TOLERANCES for Impression Die Forgings
There are practical limitations in dimensions and other characteristics of forged parts or products which vary according to the part or product and the producer's equipment. The degree of precision attainable in the manufacture of forged parts or products is dictated by the essential character of forging equipment and unavoidable contingencies in forging operations.
Theoretical exactness is seldom attained, and it is therefore necessary to make allowance for deviations. The tolerances set forth herein represent what the Forging Industry Association believes to be typical within the industry, as determined by actual measurements of forgings produced under normal operating conditions on standard forging equipment.
Experience within the industry shows that dimensional variations in forging are commonly functions of the dimensions involved, and the tolerances herein are based upon this observed fact.
The experience of producers and purchasers of forged parts and products indicates that the tolerances set forth herein will provide adequate dimensional accuracy for most applications.
THE TOLERANCES OUTLINED HEREIN ARE GUIDELINES BASED ON HISTORICAL, AVERAGED DATA. THE TERMS OF EACH TRANSACTION BETWEEN A FORGING PRODUCER AND A PURCHASER, INCLUDING TOLERANCES APPLICABLE TO THAT TRANSACTION, MUST BE NEGOTIATED AND CONFIRMED IN ADVANCE OF PRODUCTION.
There are several special ways of providing closer tolerances on selected dimensions on forgings with added operations. These include, cold and warm coining to achieve closer thickness tolerances, using special pressure padded trimmers for improving straightness, cold sizing of holes for improved tolerances on hot pierced holes, and warm forging as a manufacturing process. Be sure to contact technical personnel at your forging source for help in determining such special capabilities.

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GUIDELINE TOLERANCES FOR IMPRESSION DIE FORGINGS
A word about national standard ASME Y14.5. This tolerance guide provides dimensioning and tolerancing that is considered linear and not geometric. Geometric dimensioning and tolerancing to ASME's ANSI Y14.5M standard are being increasingly applied to forged products. Giving consideration to the fact that forgings undergo dimensional changes due to cooling and because forgings are formed in most cases between two impression dies that are not precisely on the same centerline, the ANSI Y14.5M guidelines for tolerancing are not totally appropriate to forgings.
These are reasons for FIA to refer also to the 1989 version of ASME Y14.8M an American National Standard for "Engineering Drawing and Related Document Practices for Castings and Forgings". This document more closely interprets the needed dimensional and tolerance modifications for forgings discussed in this booklet.
PRINTS AND SPECIFICATIONS
It is important that forging drawing be accurate and complete. The purchaser should indicate his first operation locating points, normally a part of the drawing, and give prior notice should these points be changed.
It is equally important that the purchaser provide drawings of the finish machined part, or equivalent information. This will assist in the design of forging dies and tools, and in establishing effective inspection procedures.
Unless the purchaser's drawings and specifications direct otherwise, all dimensions are normally assumed to refer to lines intersecting at right angles to each other (commonly referred to as X, Y, and Z axes). Furthermore, unless the purchaser's drawings or specifications direct otherwise, circular shapes are normally assumed to be figures of revolution with a center on an axis, and all circular dimensions are normally shown as diameters.
GENERAL
All individual tolerances apply to each and every forged part unless specifically noted otherwise.
Tolerances as stated in all tables are considered for use by final inspection departments at the forge plant and/or by receiving or by customer source inspection.
UNITS OF MEASURE
Tolerances in this publication are expressed in decimal inch with metric equivalents (sometimes referred to as "soft" metric conversion) in the belief that this represents a practice most common in the industry at the time of publication.
NOTE: THESE ARE GUIDELINES BASED ON AVERAGES IN THE FORGING INDUSTRY. REFINEMENTS TO THE ENCLOSED TOLERANCES CAN BE MADE IN RELATIONSHIP TO SMALLER DRAFT ANGLES, TIGHTER SQUARENESS, ROUNDNESS, PARALLELISM, HOLD STEP DESIGNS AND STRAIGHTNESS. OPERATIONS CAN BE PERFORMED BY FORGE PLANTS TO PROVIDE ADDITIONAL SERVICES WHICH IN MANY CASES REPLACE THE NEED FOR MACHINING.
DIMENSIONAL PRACTICES FOR FORGING DRAWINGS
The following procedures will apply concerning dimensioning on forging drawings: (1) Metric System _ Metric dimensions on forging drawings will be extended to one place decimal millimeter for both part dimensions and tolerances (0.1); and (2) Decimal Inch System _ Inch units of measure on forging drawings will be extended to two place decimals for both part dimensions and tolerances (0.01).
FORGINGS PRODUCED ON HAMMERS AND PRESSES LENGTH/WIDTH TOLERANCES
SCOPE
1. Length/Width Tolerances represent variations in dimensions measured parallel to the fundamental parting line of the dies. Normally, they are in addition to tolerances for die wear.
TOLERANCE
2. The Length/Width Tolerance is ±0.003 mm per mm, ±0.003 in. per inch and applies to all dimensions of length/width including diameters. This tolerance includes allowance for shrinkage, die sinking and die polishing variations. (The minimum should be plus or minus 0.8 mm or 0.03 in.)
UNITS OF MEASURE
3. Length/Width Tolerances, normally combined with tolerances for die wear are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

3.00

76.2

6.00

152.4

11.00

279.4


DIE WEAR TOLERANCES
SCOPE
1. Die wear varies according to the material that is forged and the shape of the forging. Consequently, Die Wear Tolerances for various materials are applied in addition to Length/Width Tolerances on dimensions pertaining to forged surfaces only. Die Wear Tolerances do not apply on centertocenter dimensions. (See example 4 ).
TOLERANCE
2. (a) Die Wear Tolerances for all length, width, and diameter dimensions under 750 mm or 30 in. are computed by multiplying the largest length or diameter (measured parallel to the fundamental parting line of the dies) by the appropriate factor in Table I below. Die Wear Tolerances for all length, width and diameter dimensions over 750 mm or 30 in. are taken directly from Table I.
(b) Die Wear Tolerances on external dimensions are expressed as plus values only. (See examples 5 and 6.) Die Wear Tolerances on internal dimensions are expressed as minus values only. (See examples 7 and 8.)
(c) Die Wear Tolerances per surface, on both external and internal dimensions are onehalf the computed amount.
NOTE:
Allowances for die wear occuring on dimensions measured perpendicular to the fundamental parting line of the dies are included in Die Closure Tolerances (Table II).
TABLE I: DIE WEAR TOLERANCES
Materials 
Under 30 in. or 750 mm Factor (in./inch) (mm/millimeter) 
Over 30 in. or 750 mm Constant 
in. 
mm 
Carbon, Low Alloys 
0.005 
0.15 
3.81 
Stainless 
0.007 
0.21 
5.33 
Heat Resistant Alloy 
0.009 
0.27 
6.86 
Titanium 
0.009 
0.27 
6.86 
Aluminum 
0.004 
0.12 
3.05 
Brass & Copper 
0.004 
0.12 
3.05 
UNITS OF MEASURE
3. Die Wear Tolerances combined with Length/Width Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or .01 in the inch system.
LIMITATIONS
4. The male portions of dies may, in special situations, tend to mushroom or upset rather than wear. In such cases, the requirements of the forging should be confirmed by purchaser and producer in advance of production.

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

0.07

1.8

0.09

2.3

3.00

76.2

6.00

152.4

11.00

279.4


COMPUTATION
MATERIAL: CARBON STEEL
(DIMENSIONS UNDER 30 IN. OR 750 mm)
EXAMPLE 1
(SEE FIGURE 2)

Tolerance on Length Dimension 

Plus 
Minus 

Length (mm) x Length/Width Tolerance factor 
= 279.4 x 0.003 = 
0.839 
0.839 
METRIC 
Length (mm) x Die Wear Tolerance factor 
= 279.4 x 0.005 = 
1.397 
___ 

(Table I) 

+2.236 
0.839 

Raised to the next highest 0.1mm 

+2.3 
0.9* 


Length x Length/Width Tolerance factor 
= 11 x 0.003 = 
0.033 
0.033 
INCH 
Length x Die Wear Tolerance factor 
= 11 x 0.005 = 
0.055 
___ 

(Table I)


+0.088 
0.033 

Raised to the next highest 0.01 in. 

+0.09 
0.04 
*Variance due to rounding
BACK TO TOP
EXAMPLE 2 (DIMENSIONS OVER 30 IN. OR 750 mm)
METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Length (mm) x Length/Width Tolerance factor 
= 
787.4 
x 
0.003 
= 
2.362 
2.362 

Length (mm) x Die Wear Tolerance factor 
= 
3.81 
x 
0.005 
= 
3.81 
  

(Table I) 





+6.172 
2.362 

Raised to the next highest 0.1mm 





+6.2 
2.4 


Length x Length/Width Tolerance factor 
= 
31 
x 
0.003 
= 
0.093 
0.093 
INCH 
Length x Die Wear Tolerance factor 
= 

x 
0.15 
= 
0.15 
  

(Table I)






+0.243 
0.093 

Raised to the next highest 0.01 in. 





+.25 
0.1 
EXAMPLE 3
(SEE FIGURE 2)
METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Length (mm) x Length/Width Tolerance factor 
= 
76.2 
x 
0.003 
= 
0.229 
0.229 

Greatest Length (mm) x Die Wear Tolerance factor 
= 
279.41 
x 
0.005 
= 
1.397 
  

(Table I) 





+1.626 
0.229 

Raised to the next highest 0.1mm 





+1.7 
0.3 

Minimum Tolerance 





.8 



Wide Length/Width Tolerance factor 
= 
3 
x 
0.003 
= 
0.009 
0.009 
INCH 
Greatest Length x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
0.55 
  

(Table I)






+0.064 
0.009 

Raised to the next highest 0.01 in. 





+.0.07 
0.01 

Minimum Tolerance 





0.03 

EXAMPLE 4
(SEE FIGURE 2)
<METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Dimension (mm) x Length/Width Tolerance factor 
= 
152.4 
x 
0.003 
= 
0.457 
0.457 

Raised to the next highest 0.1 mm 





+0.5 
0.5 

Minimum Tolerance 





+0.8 
0.8 


Dimension x Length/Width Tolerance factor 
= 
6 
x 
0.003 
= 
0.018 
0.018 
INCH 
Raised to the next highest 0.01 in. 
= 




+0.02 
0.02 

Minimum Tolerance 




+0.03 
0.03 

BACK TO TOP

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

0.07

1.8

0.09

2.3

4.00

101.6

11.00

279.4


COMPUTATION EXTERNAL DIMENSIONS
MATERIAL: CARBON STEEL
EXAMPLE 5 (SEE FIGURE 3)
METRIC 
Tolerance on External Dimension 





Plus 
Minus 
Diameter (mm) x Length/Width Tolerance factor 
= 
279.4 
x 
0.003 
= 
0.839 
0.839 

Diameter (mm) x Die Wear Tolerance factor 
= 
79.4 
x 
0.005 
= 
1.397 
  

(Table I) 





+2.2236 
0.839 

Raised to the next highest 0.1mm 





+2.3 
0.9* 


Diameter x Length/Width Tolerance factor 
= 
11 
x 
0.033 
= 
0.033 
0.033 
INCH 
Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.055 
= 
0.055 
  

(Table I)






+0.243 
0.033 

Raised to the next highest 0.01 in. 





+0.09 
0.04 
EXAMPLE 6 (SEE FIGURE 3)
METRIC 
Tolerance on External Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
101.6 
x 
0.003 
= 
0.305 
0.305 

Largest Diameter x Die Wear Tolerance factor (Table I) 
= 
279.4 
x 
0.005 
= 
1.397 
  







+1.702 
0.3 

Raised to the next highest 0.1mm 





+1.8 


Minimum Tolerance 





+0.8 



Diameter x Length/Width Tolerance factor 
= 
4 
x 
0.033 
= 
0.012 
0.012 
INCH 
Largest Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
0.055 
  

(Table I)






+0.067 
0.012 

Raised to the next highest 0.01 in. 





+0.07 
0.02 

Minimum Tolerance 





0.03 

BACK TO TOP

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.07

1.8

0.09

2.3

2.00

50.8

9.00

228.6


COMPUTATION EXTERNAL DIMENSIONS
MATERIAL: CARBON STEEL
EXAMPLE 7 (SEE FIGURE 4)
METRIC 
Tolerance on Internal Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
228.6 
x 
0.003 
= 
0.686 
0.686 

Largest Diameter (mm) x Die Wear Tolerance factor 
= 
279.4 
x 
0.005 
= 
— — 
1.397 

(Table I) 





+0.686 
2083 

Raised to the next highest 0.1mm 





+0.07 
2.1 

Minimum Tolerance 




+0.8 




Diameter x Length/Width Tolerance factor 
= 
9 
x 
0.033 
= 
0.027 
0.033 
INCH 
Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
— — 
0.055 

(Table I)






+0.027 
0.082 

Raised to the next highest 0.01 in. 





+0.03 
0.09 
EXAMPLE 8 (SEE FIGURE 4)
METRIC 
Tolerance on Internal Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
50.8 
x 
0.003 
= 
0.152 
0.152 

Largest Diameter x Die Wear Tolerance factor (Table I) 
= 
279.4 
x 
0.005 
= 
— — 
1.397 







+0.152 
1.549 

Raised to the next highest 0.1mm 





+0.2 
1.6 

Minimum Tolerance 




+0.8 




Diameter x Length/Width Tolerance factor 
= 
2 
x 
0.003 
= 
0.006 
0.006 
INCH 
Largest Length x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
— — 
0.055 

(Table I)






+0.006 
0.061 

Raised to the next highest 0.01 in. 





+0.01 
0.07 

Minimum Tolerance 




+0.03 


BACK TO TOP
DIE CLOSURE TOLERANCES
SCOPE
1. Die Closure Tolerances relate to variations in thickness of forgings as affected by the closing of the dies and die wear, and pertain to variations in dimensions crossing the fundamental parting line.
TOLERANCE
2. Die Closure Tolerances on forgings are based on the projected area of the forging at the trim line, not including flash, but including all areas to be subsequently punched out, and are applied as plus tolerances only. See Table II, below.
TABLE II: DIE CLOSURE TOLERANCES
TABULATED FIGURES ARE PLUS VALUES ONLY


Area at the Trim Line Flash not included, expressed in square millimeters

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
1.1 
1.6 
2.3 
3.3 
4.1 
4.9 
6.4 
Stainless 
1.6 
2.3 
3.4 
4.1 
4.9 
6.4 
7.9 
Heat Resistant Alloy 
1.6 
2.3 
3.4 
4.9 
6.4 
7.9 
9.7 
Titanium 
1.6 
2.3 
3.4 
4.9 
6.4 
7.9 
9.7 
Aluminum 
1.1 
1.3 
1.8 
2.3 
3.4 
4.9 
6.4 
Brass & Copper 
1.1 
1.3 
1.8 
2.3 
3.4 
4.9 
6.4 


Area at the Trim Line Flash not included, expressed in square inches

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
0.04 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Stainless 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
0.31 
Heat Resistant Alloy 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Titanium 
0.06 
0.09 
0.13 
0.25 
0.25 
0.31 
0.38 
Aluminum 
0.04 
0.05 
0.07 
0.13 
0.13 
0.19 
0.25 
Brass Copper 
0.04 
0.05 
0.07 
1.13 
0.13 
0.19 
0.25 
BACK TO TOP
UNITS OF MEASURE
3 .
Die Closure Tolerances are expressed decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.13 
3.4 
2.00 
50.8 

MATCH TOLERANCES
SCOPE
1. (a) Match Tolerances relate to displacement of a point in one diehalf from the corresponding point in the opposite diehalf in any direction parallel to the fundamental parting line of the dies. (Values from Table III must be doubled when specified as F.I.R. or T.I.R.)
(b) Match Tolerances are applied separately and independently to all other tolerances. Where possible, measurements are made at areas of the forging unaffected by die wear.
TOLERANCE
2. Match Tolerances are based on weight of the forging after trimming and are expressed as decimal inch or decimal millimeters according to Table III, below.
MEASURING FOR MATCH TOLERANCES
3 . In cases where measurements for determining match tolerances must be made from surfaces of the forging where uneven wearing of the dies has caused surplus stock, accuracy depends on making the proper allowances for these wearcaused surpluses, and eliminating their influence from the computation.
UNITS OF MEASURE
4. Match Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.
TABLE III: MATCH TOLERANCES


Weights of Forgings after Trimming, in Pounds

METRIC 
Materials 
0 to 2.5 
Over 2.5 to 12.5 
Over 12.5 to 25 
Over 25 to 50 
Over 50 to 100 
Over 100 to 250 
Over 250 to 500 
Over 500 
Carbon, Low Alloys 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
300, 400 Stainless Steels 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Heat Resistant Alloy 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Titanium 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Aluminum 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
Brass & Copper 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 


Weights of Forgings after Trimming, in Pounds

INCH 
Materials 
0 to 5 
Over 5 to 25 
Over 25 to 50 
Over 50 to 100 
Over 100 to 200 
Over 200 to 500 
Over 500 to 1000 
Over 1000 
Carbon, Low Alloys 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
300, 400 Stainless Steels 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Heat Resistant Alloy 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Titanium 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Aluminum 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
Brass & Copper 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
Formula refers to Figure 6
D = Match Tolerance or displacement
A = Projected maximum overall dimensions measured parallel to the main parting line of the dies.
B = Projected minimum overall dimensions measured parallel to the main parting line of the dies.


AB 
NOTE: F.I.R. or T.I.R. or AB = 2D D= 
2 

BACK TO TOP
RADII TOLERANCES
SCOPE
1. Radii Tolerances relate to all fillet radii and corner radii.
TOLERANCES
2. Radii Tolerances are plus or minus onehalf the specified radii, except where corner radii are affected by subsequent removal of draft by trimming, broaching or punching. If draft is removed as result of trimming, broaching or punching, the minus radius tolerance (0.5 of specified radius) is commonly modified to allow a square corner to be formed. (See Figures 8 and Example 10.)
UNITS OF MEASURE
3.
Radii Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.06 
1.6 
0.07 
18 
0.13 
3.4 
0.025 
6.4 

COMPUTATION
EXAMPLE 9
(SEE FIGURE 7)
METRIC 
3.4 mm radius is specified 




Max radius 
= 
1.5 x 3.4 mm 
= 
5.1. mm radius 
Min radius 
= 
0.5 x 2.4 mm 
= 
1.7 mm radius 

6.4 mm radius is specified 




Max radius 
= 
1.5 x 6.4 mm 
= 
9.4 mm radius 
Min radius 
= 
0.5 x 6.4 mm 
= 
3.2 radius 
BACK TO TOP
EXAMPLE 9 (continued)
(SEE FIGURE 7)
INCH 
0.13 in. radius is specified 




Max radius 
= 
1.5 x 0.13 in 
= 
0.195 in. radius 
Raised to the next highest 

0.01in 
= 
1.7 mm radius 
Min radius 
= 
0.5 x 0.13 in 
= 
0.065 in. radius 

Raised to the next highest 0.01 in 


= 
0.07 in. radius 

0.25 mm radius is specified 




Max. radius 
= 
1.5 x 0.25 in 

0.375 in. radius 
Raised to the next highest 

0.01 in 
= 
0.38 in. radius 
Min radius 
= 
0.5 x 0.25 in 
= 
0.13 in radius 

METRIC CONVERSION

INCH 
mm 
0.13 
34 

EXAMPLE 10
(SEE FIGURE 8)
METRIC 
3.4 mm radius is specified 




Max radius 
= 
1.5 x 3.4 mm 
= 
5.1. mm radius 
Min radius = 0 mm 





INCH 
0.13 mm radius is specified 




Max radius 
= 
1.5 x 6.4 mm 
= 
9.4 mm radius 
Min radius = 0 in. 


= 

BACK TO TOP
EXTREMITY TOLERANCES
SCOPE
1. Extremity Tolerances relate to variations in height of protrusions (steps) which are perpendicular to the fundamental parting line and are independent of die closure, die wear and other factors dealt with in this book. This tolerance applies only to steps that are contained in one die.
TOLERANCE
2. Tolerances on extremities are determined by taking the step dimension times ±0.005 inch per inch or millimeter per millimeter. This tolerance includes allowances for: nonfill, shrinkage, die sinking, polishing variations, and special die wear considerations. This tolerance is in addition to the Die Closure Tolerance. Minimum tolerance should be ±0.8 mm or 0.03 in.
UNITS OF MEASURE
3. Extremity Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raided to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.03 
0.8 
0.06 
1.6 
1.00 
25.4 
12.00 
304.8 

EXAMPLE 11
FORGINGS HAVING PERPENDICULAR EXTREMETIES
METRIC 


Plus 
Minus 
Extremity Tolerance (±0.005 mm per millimeter) for the 305 mm step dimension 
305 x 0.005 = 
1.525 
1.525 
Raised to the next highest 0.1mm 

+1.6 
1.6 

INCH 
Extremity Tolerance (±0.005 in. per inch) for the 12 in. step dimension 




12 x 0.005 = 
+0.060 
0.060 
Min radius = 0 in. 



BACK TO TOP
FLASH EXTENSION TOLERANCES
SCOPE
1. Flash Extension Tolerances are based on weight of the forging after trimming, and related to the amount of flash extension. Flash is measured from the body of the forging to the trimmed edge of the flash.
TOLERANCES
2. Flash Extension Tolerances are expressed in inches or millimeters according to Table IV below.
UNITS OF MEASURE
3. Flash Extension Tolerances are expressed as decimal inch, in units of 0.01 or greater and expressed as decimal millimeter in units of 0.1 mm or greater.
TABLE IV


Materials

METRIC 
Weights of Forgings After Trimming, in kilograms 
Carbon Low Alloy & Aluminum 
Stainless Heat Resistant Alloys & Titanium 
Brass 7 Copper 
5 and under 
0 to 0.8 
0 to 1.6 
0 to 0.8 
Over 5 to 10 incl. 
0 to 1.6 
0 to 2.3 
0 to 1.6 
Over 10 to 25 incl. 
0 to 2.3 
0 to 3.3 
0 to 2.3 
Over 25 to 50 incl. 
0 to 3.3 
0 to 4.9 
0 to 3.3 
Over 50 to 100 incl. 
0 to 4.9 
0 to 6.4 
0 to 4.9 
Over 100 to 250 incl. 
0 to 6.4 
0 to 7.9 
0 to 6.4 

Over 250 to 500 incl. 
0 to 7.9 
0 to 9.7 
0 to 7.9 

Over 500 
0 to 9.7 
0 to 12.7 
0 to 9.7 
BACK TO TOP
TABLE IV (Continued)


Materials

METRIC 
Weights of Forgings After Trimming, in kilograms 
Carbon Low Alloy & Aluminum 
Stainless Heat Resistant Alloys & Titanium 
Brass & Copper 
5 and under 
0 to 0.03 
0 to 0.06 
0 to 0.03 
Over 5 to 25 incl. 
0 to 0.06 
0 to 0.09 
0 to 0.06 
Over 25 to 50 incl. 
0 to 0.09 
0 to 0.13 
0 to 0.09 
Over 50 to 100 incl. 
0 to 0.13 
0 to 0.19 
0 to 0.13 
Over 100 to 200 incl. 
0 to 0.19 
0 to 0.25 
0 to 0.19 
Over 200 to 500 incl. 
0 to 0.25 
0 to 0.31 
0 to 0.25 

Over 500 to 1000 incl. 
0 to 0.31 
0 to 0.38 
0 to 0.31 

Over 1000 
0 to 0.38 
0 to 0.50 
0 to 0.38 
STRAIGHTNESS TOLERANCES
SCOPE
1. (a) Straightness Tolerances relate to deviations of surfaces and centerlines from the specified contour. Straightness Tolerances are applied independently of, and in addition to, all other tolerances.
(b) Four general classes of shapes have been selected for guidelines in choosing appropriate Straightness Tolerances.
CLASSES OF SHAPES
Class 
Shape of Forging 
Examples 
A 
A Elongated Length dimension greater than width or height 
long connecting rods, shafts, levers, etc. 
B 
Flat and thin 
disc, plates, etc. 
C 
Flat and thin with protrusion at right angles to the parting line 
wear plates, crawler track shoes 
D 
Blocktype forgings with neither length, width. nor thickness being predominant 
pump or valve bodies steam chests, etc. 
UNITS OF MEASURE
2. 

Straightness Tolerances are expressed as decimal inch, in units of 0.01 or greater and expressed as decimal millimeter in units of 0.1 mm or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.01 in the inch system or 0.1 in the metric system.

BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS
3. 
(a) 
CLASS A Shapes (Elongated _ Length dimensions greater than width or height) Tolerance: 0.003 in. per inch or mm per millimeter of the greatest dimension. 

METRIC CONVERSION

INCH 
mm 
0.04 
1.1 
11.0 
279.4 

EXAMPLE 12
(SEE FIGURE 11)
METRIC 
Greatest dimension x Straightness Tolerance 
279.4 x 0.003 = 
0.84 
Raised to the next highest 0.1 mm 

0.9 
Straightness Tolerance for CLASS A Shape in Figure 11 

0.9 

From true center lines in any plane 

INCH 
Greatest dimension x Straightness Tolerant 
11 x 0.003 = 
0.033 
Raised to the next highest 0.01 in. 

0.04 
Straightness Tolerance for CLASS A Shape in Figure 11 

0.04 

From true center lines in any plane 


BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS (continued)
(b) Class B Shapes (flat and thin)
Tolerance: Straightness Tolerance for CLASS B Shapes as shown in Table V.
TABLE V: STRAIGHTNESS TOLERANCES


Area at the Trim Line Flash not included, expressed in square millimeters

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
0.9 
1.6 
2.3 
3.3 
4.1 
4.9 
6.4 
Stainless 
1.6 
2.3 
3.3 
4.1 
4.8 
6.4 
7.9 
Heat Resistant Alloy 
1.6 
2.3 
3.3 
4.8 
6.4 
7.9 
9.7 
Titanium 
1.6 
2.3 
3.3 
4.8 
6.4 
7.9 
9.7 
Aluminum 
0.8 
0.8 
1.5 
2.3 
3.3 
4.8 
6.4 
Brass & Copper 
0.8 
0.8 
2.5 
2.3 
3.3 
4.8 
6.4 


Area at the Trim Line Flash not included, expressed in square millimeters

INCH 
Materials 
10 and under 
Over 10 to 30 incl. 
Over 30 to 50 incl. 
Over 50 to 100 incl. 
Over 100 to 50 incl. 
Over 500 to 1000 incl. 
Over 1000 
Carbon, Low Alloys 
0.04 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Stainless 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
0.31 
Heat Resistant Alloy 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Titanium 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Aluminum 
0.04 
0.05 
0.07 
0.09 
0.13 
0.19 
0.25 
Brass & Copper 
0.04 
0.05 
0.07 
0.09 
0.13 
0.19 
0.25 
BACK TO TOP

METRIC CONVERSION

INCH 
mm 
0.19 
4.9 
30.00 
762.0 
707.00 
456,038.0 

EXAMPLE 13
(SEE FIGURE 12 and 13)
METRIC 
Computed area at Trim Line 
456,038 sq. mm 
Appropriate value from Table V 
4.9 mm 
Straightness Tolerance for CLASS B Shape in Figures 12 and 13 
4.9 mm 


From the highest to lowest point of contour 
INCH 
Computed area at Trim Line 
707 Sq.in, 
Appropriate value from Table V 
0.19 in. 
Straightness Tolerance for CLASS B Shape in Figures 12 and 13 
0.19 in. 


From the highest to lowest point of contour 
BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS (continued)
(c) CLASS C Shapes (flat and thin with protrusion at right angles to the parting line)
Tolerance: The Straightness Tolerance on the flat portion of CLASS C Shapes is computed first. It is considered separately from the tolerance on the protruding portion and is determined in an identical manner as for CLASS B Shapes using Table V. The Straightness Tolerance on a protrusion is 0.003 in. per inch or mm per millimeter.

METRIC CONVERSION

INCH 
mm 
0.04 
1.1 
0.19 
4.9 
12.00 
304.8 
30.00 
762.0 

EXAMPLE 14
(SEE FIGURE 14)
METRIC 
Material: Carbon Steel 
= 
456,038 sq. mm 
The Tolerance on flat portion is computed first: 
= 
4.9 mm 
Computed area at Trim Line 
= 
4.9 mm 
Appropriate value from Table V 

Straightness Tolerance applied to flat portion 



From the highest to lowest point of contour 
INCH 
Computed area at Trim Line 
= 
707 Sq. In. 
Appropriate value from Table V 
= 
0.19 in. 
Straightness Tolerance applied to flat portion 
= 
0.19 in. 


From the highest to lowest point of contour 
BACK TO TOP
EXAMPLE 15
METRIC 
The Protrusion is checked against a line perpendicular to the plane established for checking the flat portion: 
Protrusion x Straightness 
Tolerance = 304.8 x 0.003 
= 
0.91 
Raised to the next highest 0.1 mm 
= 
1.0 

From true center lines in any plane 

INCH 
Protrusion x Straightness 


Tolerance = 12 in. x 0.003 
= 
0.036 
Raised to the next highest 0.01 in. 
= 
0.04 

From true center lines in any plane 

(d) 
CLASS D SHAPES (blocktype forgings with neither length, width nor thickness being predominant) 





Tolerance: Where tolerances are desired, agreement between purchaser and forging producer is normally reached before production proceeds.

DRAFT ANGLE TOLERANCES
SCOPE
1. 

Draft Angle Tolerances apply to all draft angles, specified on drawings that are not affected by subsequent operations. 
TOLERANCE
2. 

Draft Angle Tolerances are +2°0° unless modified by prior agreement between purchaser and producer. 

EXAMPLE 15
METRIC 
The Protrusion is checked against a line perpendicular to the plane established for checking the flat portion: 
Protrusion x Straightness 
Tolerance = 304.8 x 0.003 
= 
0.91 
Raised to the next highest 0.1 mm 
= 
1.0 

From true center lines in any plane 

INCH 
Protrusion x Straightness 


Tolerance = 12 in. x 0.003 
= 
0.036 
Raised to the next highest 0.01 in. 
= 
0.04 

From true center lines in any plane 

(d) 
CLASS D SHAPES (blocktype forgings with neither length, width nor thickness being predominant) 





Tolerance: Where tolerances are desired, agreement between purchaser and forging producer is normally reached before production proceeds.

DRAFT ANGLE TOLERANCES
SCOPE
1. 

Draft Angle Tolerances apply to all draft angles, specified on drawings that are not affected by subsequent operations. 
TOLERANCE
2. 

Draft Angle Tolerances are +2°0° unless modified by prior agreement between purchaser and producer. 

BACK TO TOP
SURFACE TOLERANCES
SCOPE
1. 

Surface Tolerances relate to depth of dressouts, scale pits and other imperfections on the surface of forgings. 
TOLERANCES AND CONDITIONS
2. 
(a) 
Dressouts, scale pits and other imperfections are commonly allowed on surfaces to be finish machined unless purchaser's specification or drawing states otherwise. Where purchaser specified stock for machining, these imperfections are commonly permitted to within 1.6 mm or 0.06 in. of the finished surface or to within one half of the stock allowance, whichever is smaller. . 




(b) 
Where surfaces of forgings are intended for use in "as forged" condition, surface imperfections are commonly permitted as shown in Table VI. 
METRIC 
Area at the Trim Line Flash not included, expressed in square millimeters 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
0.8 
1.2 
1.7 
2.1 
2.5 
3.2 
4.0 
METRIC 
Area at the Trim Line Flash not included, expressed in square inches 
Over 10 to 30 incl. 
Over 10 to 30 incl. 
Over 30 to 50 incl. 
Over 50 to 100 incl. 
Over 100 to 500 incl. 
Over 500 to 100 incl. 
Over Over 100 
0.03 
0.05 
0.07 
0.08 
0.10 
0.13 
0.16 

BACK TO TOP
FINISH ALLOWANCES FOR MACHINING
(For the purpose of designing a forging)
Finish allowance refers to the amount of material that is to be machined from the forging to obtain the finished part. Forging dimensions are commonly analyzed independently, with consideration given to all applicable tolerances including match, straightness, length and width but not including die wear.
TABLE VII: FINISH ALLOWANCES
Greatest Dimension 
Minimum Finish Stock Per Surface 
Over 
But Not Over 
in 
mm 
in 
mm 
in 
mm 
 
 
8 
203 
0.06 
1.6 
8 
203 
16 
406 
0.09 
2.4 
16 
406 
24 
610 
0.13 
3.2 
24 
610 
31 
914 
0.16 
4.0 
36 
916 
 
 
0.19 
4.8 
Return to Table of Contents
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TOLERANCES for Impression Die Forgings
There are practical limitations in dimensions and other characteristics of forged parts or products which vary according to the part or product and the producer\'s equipment. The degree of precision attainable in the manufacture of forged parts or products is dictated by the essential character of forging equipment and unavoidable contingencies in forging operations.
Theoretical exactness is seldom attained, and it is therefore necessary to make allowance for deviations. The tolerances set forth herein represent what the Forging Industry Association believes to be typical within the industry, as determined by actual measurements of forgings produced under normal operating conditions on standard forging equipment.
Experience within the industry shows that dimensional variations in forging are commonly functions of the dimensions involved, and the tolerances herein are based upon this observed fact.
The experience of producers and purchasers of forged parts and products indicates that the tolerances set forth herein will provide adequate dimensional accuracy for most applications.
THE TOLERANCES OUTLINED HEREIN ARE GUIDELINES BASED ON HISTORICAL, AVERAGED DATA. THE TERMS OF EACH TRANSACTION BETWEEN A FORGING PRODUCER AND A PURCHASER, INCLUDING TOLERANCES APPLICABLE TO THAT TRANSACTION, MUST BE NEGOTIATED AND CONFIRMED IN ADVANCE OF PRODUCTION.
There are several special ways of providing closer tolerances on selected dimensions on forgings with added operations. These include, cold and warm coining to achieve closer thickness tolerances, using special pressure padded trimmers for improving straightness, cold sizing of holes for improved tolerances on hot pierced holes, and warm forging as a manufacturing process. Be sure to contact technical personnel at your forging source for help in determining such special capabilities.

BACK TO TOP
GUIDELINE TOLERANCES FOR IMPRESSION DIE FORGINGS
A word about national standard ASME Y14.5. This tolerance guide provides dimensioning and tolerancing that is considered linear and not geometric. Geometric dimensioning and tolerancing to ASME\'s ANSI Y14.5M standard are being increasingly applied to forged products. Giving consideration to the fact that forgings undergo dimensional changes due to cooling and because forgings are formed in most cases between two impression dies that are not precisely on the same centerline, the ANSI Y14.5M guidelines for tolerancing are not totally appropriate to forgings.
These are reasons for FIA to refer also to the 1989 version of ASME Y14.8M an American National Standard for "Engineering Drawing and Related Document Practices for Castings and Forgings". This document more closely interprets the needed dimensional and tolerance modifications for forgings discussed in this booklet.
PRINTS AND SPECIFICATIONS
It is important that forging drawing be accurate and complete. The purchaser should indicate his first operation locating points, normally a part of the drawing, and give prior notice should these points be changed.
It is equally important that the purchaser provide drawings of the finish machined part, or equivalent information. This will assist in the design of forging dies and tools, and in establishing effective inspection procedures.
Unless the purchaser\'s drawings and specifications direct otherwise, all dimensions are normally assumed to refer to lines intersecting at right angles to each other (commonly referred to as X, Y, and Z axes). Furthermore, unless the purchaser\'s drawings or specifications direct otherwise, circular shapes are normally assumed to be figures of revolution with a center on an axis, and all circular dimensions are normally shown as diameters.
GENERAL
All individual tolerances apply to each and every forged part unless specifically noted otherwise.
Tolerances as stated in all tables are considered for use by final inspection departments at the forge plant and/or by receiving or by customer source inspection.
UNITS OF MEASURE
Tolerances in this publication are expressed in decimal inch with metric equivalents (sometimes referred to as "soft" metric conversion) in the belief that this represents a practice most common in the industry at the time of publication.
NOTE: THESE ARE GUIDELINES BASED ON AVERAGES IN THE FORGING INDUSTRY. REFINEMENTS TO THE ENCLOSED TOLERANCES CAN BE MADE IN RELATIONSHIP TO SMALLER DRAFT ANGLES, TIGHTER SQUARENESS, ROUNDNESS, PARALLELISM, HOLD STEP DESIGNS AND STRAIGHTNESS. OPERATIONS CAN BE PERFORMED BY FORGE PLANTS TO PROVIDE ADDITIONAL SERVICES WHICH IN MANY CASES REPLACE THE NEED FOR MACHINING.
DIMENSIONAL PRACTICES FOR FORGING DRAWINGS
The following procedures will apply concerning dimensioning on forging drawings: (1) Metric System _ Metric dimensions on forging drawings will be extended to one place decimal millimeter for both part dimensions and tolerances (0.1); and (2) Decimal Inch System _ Inch units of measure on forging drawings will be extended to two place decimals for both part dimensions and tolerances (0.01).
FORGINGS PRODUCED ON HAMMERS AND PRESSES LENGTH/WIDTH TOLERANCES
SCOPE
1. Length/Width Tolerances represent variations in dimensions measured parallel to the fundamental parting line of the dies. Normally, they are in addition to tolerances for die wear.
TOLERANCE
2. The Length/Width Tolerance is ±0.003 mm per mm, ±0.003 in. per inch and applies to all dimensions of length/width including diameters. This tolerance includes allowance for shrinkage, die sinking and die polishing variations. (The minimum should be plus or minus 0.8 mm or 0.03 in.)
UNITS OF MEASURE
3. Length/Width Tolerances, normally combined with tolerances for die wear are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

3.00

76.2

6.00

152.4

11.00

279.4


DIE WEAR TOLERANCES
SCOPE
1. Die wear varies according to the material that is forged and the shape of the forging. Consequently, Die Wear Tolerances for various materials are applied in addition to Length/Width Tolerances on dimensions pertaining to forged surfaces only. Die Wear Tolerances do not apply on centertocenter dimensions. (See example 4 ).
TOLERANCE
2. (a) Die Wear Tolerances for all length, width, and diameter dimensions under 750 mm or 30 in. are computed by multiplying the largest length or diameter (measured parallel to the fundamental parting line of the dies) by the appropriate factor in Table I below. Die Wear Tolerances for all length, width and diameter dimensions over 750 mm or 30 in. are taken directly from Table I.
(b) Die Wear Tolerances on external dimensions are expressed as plus values only. (See examples 5 and 6.) Die Wear Tolerances on internal dimensions are expressed as minus values only. (See examples 7 and 8.)
(c) Die Wear Tolerances per surface, on both external and internal dimensions are onehalf the computed amount.
NOTE:
Allowances for die wear occuring on dimensions measured perpendicular to the fundamental parting line of the dies are included in Die Closure Tolerances (Table II).
TABLE I: DIE WEAR TOLERANCES
Materials 
Under 30 in. or 750 mm Factor (in./inch) (mm/millimeter) 
Over 30 in. or 750 mm Constant 
in. 
mm 
Carbon, Low Alloys 
0.005 
0.15 
3.81 
Stainless 
0.007 
0.21 
5.33 
Heat Resistant Alloy 
0.009 
0.27 
6.86 
Titanium 
0.009 
0.27 
6.86 
Aluminum 
0.004 
0.12 
3.05 
Brass & Copper 
0.004 
0.12 
3.05 
UNITS OF MEASURE
3. Die Wear Tolerances combined with Length/Width Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or .01 in the inch system.
LIMITATIONS
4. The male portions of dies may, in special situations, tend to mushroom or upset rather than wear. In such cases, the requirements of the forging should be confirmed by purchaser and producer in advance of production.

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

0.07

1.8

0.09

2.3

3.00

76.2

6.00

152.4

11.00

279.4


COMPUTATION
MATERIAL: CARBON STEEL
(DIMENSIONS UNDER 30 IN. OR 750 mm)
EXAMPLE 1
(SEE FIGURE 2)

Tolerance on Length Dimension 

Plus 
Minus 

Length (mm) x Length/Width Tolerance factor 
= 279.4 x 0.003 = 
0.839 
0.839 
METRIC 
Length (mm) x Die Wear Tolerance factor 
= 279.4 x 0.005 = 
1.397 
___ 

(Table I) 

+2.236 
0.839 

Raised to the next highest 0.1mm 

+2.3 
0.9* 


Length x Length/Width Tolerance factor 
= 11 x 0.003 = 
0.033 
0.033 
INCH 
Length x Die Wear Tolerance factor 
= 11 x 0.005 = 
0.055 
___ 

(Table I)


+0.088 
0.033 

Raised to the next highest 0.01 in. 

+0.09 
0.04 
*Variance due to rounding
BACK TO TOP
EXAMPLE 2 (DIMENSIONS OVER 30 IN. OR 750 mm)
METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Length (mm) x Length/Width Tolerance factor 
= 
787.4 
x 
0.003 
= 
2.362 
2.362 

Length (mm) x Die Wear Tolerance factor 
= 
3.81 
x 
0.005 
= 
3.81 
  

(Table I) 





+6.172 
2.362 

Raised to the next highest 0.1mm 





+6.2 
2.4 


Length x Length/Width Tolerance factor 
= 
31 
x 
0.003 
= 
0.093 
0.093 
INCH 
Length x Die Wear Tolerance factor 
= 

x 
0.15 
= 
0.15 
  

(Table I)






+0.243 
0.093 

Raised to the next highest 0.01 in. 





+.25 
0.1 
EXAMPLE 3
(SEE FIGURE 2)
METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Length (mm) x Length/Width Tolerance factor 
= 
76.2 
x 
0.003 
= 
0.229 
0.229 

Greatest Length (mm) x Die Wear Tolerance factor 
= 
279.41 
x 
0.005 
= 
1.397 
  

(Table I) 





+1.626 
0.229 

Raised to the next highest 0.1mm 





+1.7 
0.3 

Minimum Tolerance 





.8 



Wide Length/Width Tolerance factor 
= 
3 
x 
0.003 
= 
0.009 
0.009 
INCH 
Greatest Length x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
0.55 
  

(Table I)






+0.064 
0.009 

Raised to the next highest 0.01 in. 





+.0.07 
0.01 

Minimum Tolerance 





0.03 

EXAMPLE 4
(SEE FIGURE 2)
<METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Dimension (mm) x Length/Width Tolerance factor 
= 
152.4 
x 
0.003 
= 
0.457 
0.457 

Raised to the next highest 0.1 mm 





+0.5 
0.5 

Minimum Tolerance 





+0.8 
0.8 


Dimension x Length/Width Tolerance factor 
= 
6 
x 
0.003 
= 
0.018 
0.018 
INCH 
Raised to the next highest 0.01 in. 
= 




+0.02 
0.02 

Minimum Tolerance 




+0.03 
0.03 

BACK TO TOP

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

0.07

1.8

0.09

2.3

4.00

101.6

11.00

279.4


COMPUTATION EXTERNAL DIMENSIONS
MATERIAL: CARBON STEEL
EXAMPLE 5 (SEE FIGURE 3)
METRIC 
Tolerance on External Dimension 





Plus 
Minus 
Diameter (mm) x Length/Width Tolerance factor 
= 
279.4 
x 
0.003 
= 
0.839 
0.839 

Diameter (mm) x Die Wear Tolerance factor 
= 
79.4 
x 
0.005 
= 
1.397 
  

(Table I) 





+2.2236 
0.839 

Raised to the next highest 0.1mm 





+2.3 
0.9* 


Diameter x Length/Width Tolerance factor 
= 
11 
x 
0.033 
= 
0.033 
0.033 
INCH 
Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.055 
= 
0.055 
  

(Table I)






+0.243 
0.033 

Raised to the next highest 0.01 in. 





+0.09 
0.04 
EXAMPLE 6 (SEE FIGURE 3)
METRIC 
Tolerance on External Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
101.6 
x 
0.003 
= 
0.305 
0.305 

Largest Diameter x Die Wear Tolerance factor (Table I) 
= 
279.4 
x 
0.005 
= 
1.397 
  







+1.702 
0.3 

Raised to the next highest 0.1mm 





+1.8 


Minimum Tolerance 





+0.8 



Diameter x Length/Width Tolerance factor 
= 
4 
x 
0.033 
= 
0.012 
0.012 
INCH 
Largest Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
0.055 
  

(Table I)






+0.067 
0.012 

Raised to the next highest 0.01 in. 





+0.07 
0.02 

Minimum Tolerance 





0.03 

BACK TO TOP

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.07

1.8

0.09

2.3

2.00

50.8

9.00

228.6


COMPUTATION EXTERNAL DIMENSIONS
MATERIAL: CARBON STEEL
EXAMPLE 7 (SEE FIGURE 4)
METRIC 
Tolerance on Internal Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
228.6 
x 
0.003 
= 
0.686 
0.686 

Largest Diameter (mm) x Die Wear Tolerance factor 
= 
279.4 
x 
0.005 
= 
— — 
1.397 

(Table I) 





+0.686 
2083 

Raised to the next highest 0.1mm 





+0.07 
2.1 

Minimum Tolerance 




+0.8 




Diameter x Length/Width Tolerance factor 
= 
9 
x 
0.033 
= 
0.027 
0.033 
INCH 
Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
— — 
0.055 

(Table I)






+0.027 
0.082 

Raised to the next highest 0.01 in. 





+0.03 
0.09 
EXAMPLE 8 (SEE FIGURE 4)
METRIC 
Tolerance on Internal Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
50.8 
x 
0.003 
= 
0.152 
0.152 

Largest Diameter x Die Wear Tolerance factor (Table I) 
= 
279.4 
x 
0.005 
= 
— — 
1.397 







+0.152 
1.549 

Raised to the next highest 0.1mm 





+0.2 
1.6 

Minimum Tolerance 




+0.8 




Diameter x Length/Width Tolerance factor 
= 
2 
x 
0.003 
= 
0.006 
0.006 
INCH 
Largest Length x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
— — 
0.055 

(Table I)






+0.006 
0.061 

Raised to the next highest 0.01 in. 





+0.01 
0.07 

Minimum Tolerance 




+0.03 


BACK TO TOP
DIE CLOSURE TOLERANCES
SCOPE
1. Die Closure Tolerances relate to variations in thickness of forgings as affected by the closing of the dies and die wear, and pertain to variations in dimensions crossing the fundamental parting line.
TOLERANCE
2. Die Closure Tolerances on forgings are based on the projected area of the forging at the trim line, not including flash, but including all areas to be subsequently punched out, and are applied as plus tolerances only. See Table II, below.
TABLE II: DIE CLOSURE TOLERANCES
TABULATED FIGURES ARE PLUS VALUES ONLY


Area at the Trim Line Flash not included, expressed in square millimeters

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
1.1 
1.6 
2.3 
3.3 
4.1 
4.9 
6.4 
Stainless 
1.6 
2.3 
3.4 
4.1 
4.9 
6.4 
7.9 
Heat Resistant Alloy 
1.6 
2.3 
3.4 
4.9 
6.4 
7.9 
9.7 
Titanium 
1.6 
2.3 
3.4 
4.9 
6.4 
7.9 
9.7 
Aluminum 
1.1 
1.3 
1.8 
2.3 
3.4 
4.9 
6.4 
Brass & Copper 
1.1 
1.3 
1.8 
2.3 
3.4 
4.9 
6.4 


Area at the Trim Line Flash not included, expressed in square inches

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
0.04 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Stainless 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
0.31 
Heat Resistant Alloy 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Titanium 
0.06 
0.09 
0.13 
0.25 
0.25 
0.31 
0.38 
Aluminum 
0.04 
0.05 
0.07 
0.13 
0.13 
0.19 
0.25 
Brass Copper 
0.04 
0.05 
0.07 
1.13 
0.13 
0.19 
0.25 
BACK TO TOP
UNITS OF MEASURE
3 .
Die Closure Tolerances are expressed decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.13 
3.4 
2.00 
50.8 

MATCH TOLERANCES
SCOPE
1. (a) Match Tolerances relate to displacement of a point in one diehalf from the corresponding point in the opposite diehalf in any direction parallel to the fundamental parting line of the dies. (Values from Table III must be doubled when specified as F.I.R. or T.I.R.)
(b) Match Tolerances are applied separately and independently to all other tolerances. Where possible, measurements are made at areas of the forging unaffected by die wear.
TOLERANCE
2. Match Tolerances are based on weight of the forging after trimming and are expressed as decimal inch or decimal millimeters according to Table III, below.
MEASURING FOR MATCH TOLERANCES
3 . In cases where measurements for determining match tolerances must be made from surfaces of the forging where uneven wearing of the dies has caused surplus stock, accuracy depends on making the proper allowances for these wearcaused surpluses, and eliminating their influence from the computation.
UNITS OF MEASURE
4. Match Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.
TABLE III: MATCH TOLERANCES


Weights of Forgings after Trimming, in Pounds

METRIC 
Materials 
0 to 2.5 
Over 2.5 to 12.5 
Over 12.5 to 25 
Over 25 to 50 
Over 50 to 100 
Over 100 to 250 
Over 250 to 500 
Over 500 
Carbon, Low Alloys 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
300, 400 Stainless Steels 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Heat Resistant Alloy 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Titanium 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Aluminum 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
Brass & Copper 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 


Weights of Forgings after Trimming, in Pounds

INCH 
Materials 
0 to 5 
Over 5 to 25 
Over 25 to 50 
Over 50 to 100 
Over 100 to 200 
Over 200 to 500 
Over 500 to 1000 
Over 1000 
Carbon, Low Alloys 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
300, 400 Stainless Steels 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Heat Resistant Alloy 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Titanium 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Aluminum 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
Brass & Copper 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
Formula refers to Figure 6
D = Match Tolerance or displacement
A = Projected maximum overall dimensions measured parallel to the main parting line of the dies.
B = Projected minimum overall dimensions measured parallel to the main parting line of the dies.


AB 
NOTE: F.I.R. or T.I.R. or AB = 2D D= 
2 

BACK TO TOP
RADII TOLERANCES
SCOPE
1. Radii Tolerances relate to all fillet radii and corner radii.
TOLERANCES
2. Radii Tolerances are plus or minus onehalf the specified radii, except where corner radii are affected by subsequent removal of draft by trimming, broaching or punching. If draft is removed as result of trimming, broaching or punching, the minus radius tolerance (0.5 of specified radius) is commonly modified to allow a square corner to be formed. (See Figures 8 and Example 10.)
UNITS OF MEASURE
3.
Radii Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.06 
1.6 
0.07 
18 
0.13 
3.4 
0.025 
6.4 

COMPUTATION
EXAMPLE 9
(SEE FIGURE 7)
METRIC 
3.4 mm radius is specified 




Max radius 
= 
1.5 x 3.4 mm 
= 
5.1. mm radius 
Min radius 
= 
0.5 x 2.4 mm 
= 
1.7 mm radius 

6.4 mm radius is specified 




Max radius 
= 
1.5 x 6.4 mm 
= 
9.4 mm radius 
Min radius 
= 
0.5 x 6.4 mm 
= 
3.2 radius 
BACK TO TOP
EXAMPLE 9 (continued)
(SEE FIGURE 7)
INCH 
0.13 in. radius is specified 




Max radius 
= 
1.5 x 0.13 in 
= 
0.195 in. radius 
Raised to the next highest 

0.01in 
= 
1.7 mm radius 
Min radius 
= 
0.5 x 0.13 in 
= 
0.065 in. radius 

Raised to the next highest 0.01 in 


= 
0.07 in. radius 

0.25 mm radius is specified 




Max. radius 
= 
1.5 x 0.25 in 

0.375 in. radius 
Raised to the next highest 

0.01 in 
= 
0.38 in. radius 
Min radius 
= 
0.5 x 0.25 in 
= 
0.13 in radius 

METRIC CONVERSION

INCH 
mm 
0.13 
34 

EXAMPLE 10
(SEE FIGURE 8)
METRIC 
3.4 mm radius is specified 




Max radius 
= 
1.5 x 3.4 mm 
= 
5.1. mm radius 
Min radius = 0 mm 





INCH 
0.13 mm radius is specified 




Max radius 
= 
1.5 x 6.4 mm 
= 
9.4 mm radius 
Min radius = 0 in. 


= 

BACK TO TOP
EXTREMITY TOLERANCES
SCOPE
1. Extremity Tolerances relate to variations in height of protrusions (steps) which are perpendicular to the fundamental parting line and are independent of die closure, die wear and other factors dealt with in this book. This tolerance applies only to steps that are contained in one die.
TOLERANCE
2. Tolerances on extremities are determined by taking the step dimension times ±0.005 inch per inch or millimeter per millimeter. This tolerance includes allowances for: nonfill, shrinkage, die sinking, polishing variations, and special die wear considerations. This tolerance is in addition to the Die Closure Tolerance. Minimum tolerance should be ±0.8 mm or 0.03 in.
UNITS OF MEASURE
3. Extremity Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raided to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.03 
0.8 
0.06 
1.6 
1.00 
25.4 
12.00 
304.8 

EXAMPLE 11
FORGINGS HAVING PERPENDICULAR EXTREMETIES
METRIC 


Plus 
Minus 
Extremity Tolerance (±0.005 mm per millimeter) for the 305 mm step dimension 
305 x 0.005 = 
1.525 
1.525 
Raised to the next highest 0.1mm 

+1.6 
1.6 

INCH 
Extremity Tolerance (±0.005 in. per inch) for the 12 in. step dimension 




12 x 0.005 = 
+0.060 
0.060 
Min radius = 0 in. 



BACK TO TOP
FLASH EXTENSION TOLERANCES
SCOPE
1. Flash Extension Tolerances are based on weight of the forging after trimming, and related to the amount of flash extension. Flash is measured from the body of the forging to the trimmed edge of the flash.
TOLERANCES
2. Flash Extension Tolerances are expressed in inches or millimeters according to Table IV below.
UNITS OF MEASURE
3. Flash Extension Tolerances are expressed as decimal inch, in units of 0.01 or greater and expressed as decimal millimeter in units of 0.1 mm or greater.
TABLE IV


Materials

METRIC 
Weights of Forgings After Trimming, in kilograms 
Carbon Low Alloy & Aluminum 
Stainless Heat Resistant Alloys & Titanium 
Brass 7 Copper 
5 and under 
0 to 0.8 
0 to 1.6 
0 to 0.8 
Over 5 to 10 incl. 
0 to 1.6 
0 to 2.3 
0 to 1.6 
Over 10 to 25 incl. 
0 to 2.3 
0 to 3.3 
0 to 2.3 
Over 25 to 50 incl. 
0 to 3.3 
0 to 4.9 
0 to 3.3 
Over 50 to 100 incl. 
0 to 4.9 
0 to 6.4 
0 to 4.9 
Over 100 to 250 incl. 
0 to 6.4 
0 to 7.9 
0 to 6.4 

Over 250 to 500 incl. 
0 to 7.9 
0 to 9.7 
0 to 7.9 

Over 500 
0 to 9.7 
0 to 12.7 
0 to 9.7 
BACK TO TOP
TABLE IV (Continued)


Materials

METRIC 
Weights of Forgings After Trimming, in kilograms 
Carbon Low Alloy & Aluminum 
Stainless Heat Resistant Alloys & Titanium 
Brass & Copper 
5 and under 
0 to 0.03 
0 to 0.06 
0 to 0.03 
Over 5 to 25 incl. 
0 to 0.06 
0 to 0.09 
0 to 0.06 
Over 25 to 50 incl. 
0 to 0.09 
0 to 0.13 
0 to 0.09 
Over 50 to 100 incl. 
0 to 0.13 
0 to 0.19 
0 to 0.13 
Over 100 to 200 incl. 
0 to 0.19 
0 to 0.25 
0 to 0.19 
Over 200 to 500 incl. 
0 to 0.25 
0 to 0.31 
0 to 0.25 

Over 500 to 1000 incl. 
0 to 0.31 
0 to 0.38 
0 to 0.31 

Over 1000 
0 to 0.38 
0 to 0.50 
0 to 0.38 
STRAIGHTNESS TOLERANCES
SCOPE
1. (a) Straightness Tolerances relate to deviations of surfaces and centerlines from the specified contour. Straightness Tolerances are applied independently of, and in addition to, all other tolerances.
(b) Four general classes of shapes have been selected for guidelines in choosing appropriate Straightness Tolerances.
CLASSES OF SHAPES
Class 
Shape of Forging 
Examples 
A 
A Elongated Length dimension greater than width or height 
long connecting rods, shafts, levers, etc. 
B 
Flat and thin 
disc, plates, etc. 
C 
Flat and thin with protrusion at right angles to the parting line 
wear plates, crawler track shoes 
D 
Blocktype forgings with neither length, width. nor thickness being predominant 
pump or valve bodies steam chests, etc. 
UNITS OF MEASURE
2. 

Straightness Tolerances are expressed as decimal inch, in units of 0.01 or greater and expressed as decimal millimeter in units of 0.1 mm or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.01 in the inch system or 0.1 in the metric system.

BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS
3. 
(a) 
CLASS A Shapes (Elongated _ Length dimensions greater than width or height) Tolerance: 0.003 in. per inch or mm per millimeter of the greatest dimension. 

METRIC CONVERSION

INCH 
mm 
0.04 
1.1 
11.0 
279.4 

EXAMPLE 12
(SEE FIGURE 11)
METRIC 
Greatest dimension x Straightness Tolerance 
279.4 x 0.003 = 
0.84 
Raised to the next highest 0.1 mm 

0.9 
Straightness Tolerance for CLASS A Shape in Figure 11 

0.9 

From true center lines in any plane 

INCH 
Greatest dimension x Straightness Tolerant 
11 x 0.003 = 
0.033 
Raised to the next highest 0.01 in. 

0.04 
Straightness Tolerance for CLASS A Shape in Figure 11 

0.04 

From true center lines in any plane 


BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS (continued)
(b) Class B Shapes (flat and thin)
Tolerance: Straightness Tolerance for CLASS B Shapes as shown in Table V.
TABLE V: STRAIGHTNESS TOLERANCES


Area at the Trim Line Flash not included, expressed in square millimeters

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
0.9 
1.6 
2.3 
3.3 
4.1 
4.9 
6.4 
Stainless 
1.6 
2.3 
3.3 
4.1 
4.8 
6.4 
7.9 
Heat Resistant Alloy 
1.6 
2.3 
3.3 
4.8 
6.4 
7.9 
9.7 
Titanium 
1.6 
2.3 
3.3 
4.8 
6.4 
7.9 
9.7 
Aluminum 
0.8 
0.8 
1.5 
2.3 
3.3 
4.8 
6.4 
Brass & Copper 
0.8 
0.8 
2.5 
2.3 
3.3 
4.8 
6.4 


Area at the Trim Line Flash not included, expressed in square millimeters

INCH 
Materials 
10 and under 
Over 10 to 30 incl. 
Over 30 to 50 incl. 
Over 50 to 100 incl. 
Over 100 to 50 incl. 
Over 500 to 1000 incl. 
Over 1000 
Carbon, Low Alloys 
0.04 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Stainless 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
0.31 
Heat Resistant Alloy 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Titanium 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Aluminum 
0.04 
0.05 
0.07 
0.09 
0.13 
0.19 
0.25 
Brass & Copper 
0.04 
0.05 
0.07 
0.09 
0.13 
0.19 
0.25 
BACK TO TOP

METRIC CONVERSION

INCH 
mm 
0.19 
4.9 
30.00 
762.0 
707.00 
456,038.0 

EXAMPLE 13
(SEE FIGURE 12 and 13)
METRIC 
Computed area at Trim Line 
456,038 sq. mm 
Appropriate value from Table V 
4.9 mm 
Straightness Tolerance for CLASS B Shape in Figures 12 and 13 
4.9 mm 


From the highest to lowest point of contour 
INCH 
Computed area at Trim Line 
707 Sq.in, 
Appropriate value from Table V 
0.19 in. 
Straightness Tolerance for CLASS B Shape in Figures 12 and 13 
0.19 in. 


From the highest to lowest point of contour 
BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS (continued)
(c) CLASS C Shapes (flat and thin with protrusion at right angles to the parting line)
Tolerance: The Straightness Tolerance on the flat portion of CLASS C Shapes is computed first. It is considered separately from the tolerance on the protruding portion and is determined in an identical manner as for CLASS B Shapes using Table V. The Straightness Tolerance on a protrusion is 0.003 in. per inch or mm per millimeter.

METRIC CONVERSION

INCH 
mm 
0.04 
1.1 
0.19 
4.9 
12.00 
304.8 
30.00 
762.0 

EXAMPLE 14
(SEE FIGURE 14)
METRIC 
Material: Carbon Steel 
= 
456,038 sq. mm 
The Tolerance on flat portion is computed first: 
= 
4.9 mm 
Computed area at Trim Line 
= 
4.9 mm 
Appropriate value from Table V 

Straightness Tolerance applied to flat portion 



From the highest to lowest point of contour 
INCH 
Computed area at Trim Line 
= 
707 Sq. In. 
Appropriate value from Table V 
= 
0.19 in. 
Straightness Tolerance applied to flat portion 
= 
0.19 in. 


From the highest to lowest point of contour 
BACK TO TOP
EXAMPLE 15
METRIC 
The Protrusion is checked against a line perpendicular to the plane established for checking the flat portion: 
Protrusion x Straightness 
Tolerance = 304.8 x 0.003 
= 
0.91 
Raised to the next highest 0.1 mm 
= 
1.0 

From true center lines in any plane 

INCH 
Protrusion x Straightness 


Tolerance = 12 in. x 0.003 
= 
0.036 
Raised to the next highest 0.01 in. 
= 
0.04 

From true center lines in any plane 

(d) 
CLASS D SHAPES (blocktype forgings with neither length, width nor thickness being predominant) 





Tolerance: Where tolerances are desired, agreement between purchaser and forging producer is normally reached before production proceeds.

DRAFT ANGLE TOLERANCES
SCOPE
1. 

Draft Angle Tolerances apply to all draft angles, specified on drawings that are not affected by subsequent operations. 
TOLERANCE
2. 

Draft Angle Tolerances are +2°0° unless modified by prior agreement between purchaser and producer. 

EXAMPLE 15
METRIC 
The Protrusion is checked against a line perpendicular to the plane established for checking the flat portion: 
Protrusion x Straightness 
Tolerance = 304.8 x 0.003 
= 
0.91 
Raised to the next highest 0.1 mm 
= 
1.0 

From true center lines in any plane 

INCH 
Protrusion x Straightness 


Tolerance = 12 in. x 0.003 
= 
0.036 
Raised to the next highest 0.01 in. 
= 
0.04 

From true center lines in any plane 

(d) 
CLASS D SHAPES (blocktype forgings with neither length, width nor thickness being predominant) 





Tolerance: Where tolerances are desired, agreement between purchaser and forging producer is normally reached before production proceeds.

DRAFT ANGLE TOLERANCES
SCOPE
1. 

Draft Angle Tolerances apply to all draft angles, specified on drawings that are not affected by subsequent operations. 
TOLERANCE
2. 

Draft Angle Tolerances are +2°0° unless modified by prior agreement between purchaser and producer. 

BACK TO TOP
SURFACE TOLERANCES
SCOPE
1. 

Surface Tolerances relate to depth of dressouts, scale pits and other imperfections on the surface of forgings. 
TOLERANCES AND CONDITIONS
2. 
(a) 
Dressouts, scale pits and other imperfections are commonly allowed on surfaces to be finish machined unless purchaser\'s specification or drawing states otherwise. Where purchaser specified stock for machining, these imperfections are commonly permitted to within 1.6 mm or 0.06 in. of the finished surface or to within one half of the stock allowance, whichever is smaller. . 




(b) 
Where surfaces of forgings are intended for use in "as forged" condition, surface imperfections are commonly permitted as shown in Table VI. 
METRIC 
Area at the Trim Line Flash not included, expressed in square millimeters 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
0.8 
1.2 
1.7 
2.1 
2.5 
3.2 
4.0 
METRIC 
Area at the Trim Line Flash not included, expressed in square inches 
Over 10 to 30 incl. 
Over 10 to 30 incl. 
Over 30 to 50 incl. 
Over 50 to 100 incl. 
Over 100 to 500 incl. 
Over 500 to 100 incl. 
Over Over 100 
0.03 
0.05 
0.07 
0.08 
0.10 
0.13 
0.16 

BACK TO TOP
FINISH ALLOWANCES FOR MACHINING
(For the purpose of designing a forging)
Finish allowance refers to the amount of material that is to be machined from the forging to obtain the finished part. Forging dimensions are commonly analyzed independently, with consideration given to all applicable tolerances including match, straightness, length and width but not including die wear.
TABLE VII: FINISH ALLOWANCES
Greatest Dimension 
Minimum Finish Stock Per Surface 
Over 
But Not Over 
in 
mm 
in 
mm 
in 
mm 
 
 
8 
203 
0.06 
1.6 
8 
203 
16 
406 
0.09 
2.4 
16 
406 
24 
610 
0.13 
3.2 
24 
610 
31 
914 
0.16 
4.0 
36 
916 
 
 
0.19 
4.8 
Return to Table of Contents
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TOLERANCES for Impression Die Forgings
There are practical limitations in dimensions and other characteristics of forged parts or products which vary according to the part or product and the producer\'s equipment. The degree of precision attainable in the manufacture of forged parts or products is dictated by the essential character of forging equipment and unavoidable contingencies in forging operations.
Theoretical exactness is seldom attained, and it is therefore necessary to make allowance for deviations. The tolerances set forth herein represent what the Forging Industry Association believes to be typical within the industry, as determined by actual measurements of forgings produced under normal operating conditions on standard forging equipment.
Experience within the industry shows that dimensional variations in forging are commonly functions of the dimensions involved, and the tolerances herein are based upon this observed fact.
The experience of producers and purchasers of forged parts and products indicates that the tolerances set forth herein will provide adequate dimensional accuracy for most applications.
THE TOLERANCES OUTLINED HEREIN ARE GUIDELINES BASED ON HISTORICAL, AVERAGED DATA. THE TERMS OF EACH TRANSACTION BETWEEN A FORGING PRODUCER AND A PURCHASER, INCLUDING TOLERANCES APPLICABLE TO THAT TRANSACTION, MUST BE NEGOTIATED AND CONFIRMED IN ADVANCE OF PRODUCTION.
There are several special ways of providing closer tolerances on selected dimensions on forgings with added operations. These include, cold and warm coining to achieve closer thickness tolerances, using special pressure padded trimmers for improving straightness, cold sizing of holes for improved tolerances on hot pierced holes, and warm forging as a manufacturing process. Be sure to contact technical personnel at your forging source for help in determining such special capabilities.

BACK TO TOP
GUIDELINE TOLERANCES FOR IMPRESSION DIE FORGINGS
A word about national standard ASME Y14.5. This tolerance guide provides dimensioning and tolerancing that is considered linear and not geometric. Geometric dimensioning and tolerancing to ASME\'s ANSI Y14.5M standard are being increasingly applied to forged products. Giving consideration to the fact that forgings undergo dimensional changes due to cooling and because forgings are formed in most cases between two impression dies that are not precisely on the same centerline, the ANSI Y14.5M guidelines for tolerancing are not totally appropriate to forgings.
These are reasons for FIA to refer also to the 1989 version of ASME Y14.8M an American National Standard for "Engineering Drawing and Related Document Practices for Castings and Forgings". This document more closely interprets the needed dimensional and tolerance modifications for forgings discussed in this booklet.
PRINTS AND SPECIFICATIONS
It is important that forging drawing be accurate and complete. The purchaser should indicate his first operation locating points, normally a part of the drawing, and give prior notice should these points be changed.
It is equally important that the purchaser provide drawings of the finish machined part, or equivalent information. This will assist in the design of forging dies and tools, and in establishing effective inspection procedures.
Unless the purchaser\'s drawings and specifications direct otherwise, all dimensions are normally assumed to refer to lines intersecting at right angles to each other (commonly referred to as X, Y, and Z axes). Furthermore, unless the purchaser\'s drawings or specifications direct otherwise, circular shapes are normally assumed to be figures of revolution with a center on an axis, and all circular dimensions are normally shown as diameters.
GENERAL
All individual tolerances apply to each and every forged part unless specifically noted otherwise.
Tolerances as stated in all tables are considered for use by final inspection departments at the forge plant and/or by receiving or by customer source inspection.
UNITS OF MEASURE
Tolerances in this publication are expressed in decimal inch with metric equivalents (sometimes referred to as "soft" metric conversion) in the belief that this represents a practice most common in the industry at the time of publication.
NOTE: THESE ARE GUIDELINES BASED ON AVERAGES IN THE FORGING INDUSTRY. REFINEMENTS TO THE ENCLOSED TOLERANCES CAN BE MADE IN RELATIONSHIP TO SMALLER DRAFT ANGLES, TIGHTER SQUARENESS, ROUNDNESS, PARALLELISM, HOLD STEP DESIGNS AND STRAIGHTNESS. OPERATIONS CAN BE PERFORMED BY FORGE PLANTS TO PROVIDE ADDITIONAL SERVICES WHICH IN MANY CASES REPLACE THE NEED FOR MACHINING.
DIMENSIONAL PRACTICES FOR FORGING DRAWINGS
The following procedures will apply concerning dimensioning on forging drawings: (1) Metric System _ Metric dimensions on forging drawings will be extended to one place decimal millimeter for both part dimensions and tolerances (0.1); and (2) Decimal Inch System _ Inch units of measure on forging drawings will be extended to two place decimals for both part dimensions and tolerances (0.01).
FORGINGS PRODUCED ON HAMMERS AND PRESSES LENGTH/WIDTH TOLERANCES
SCOPE
1. Length/Width Tolerances represent variations in dimensions measured parallel to the fundamental parting line of the dies. Normally, they are in addition to tolerances for die wear.
TOLERANCE
2. The Length/Width Tolerance is ±0.003 mm per mm, ±0.003 in. per inch and applies to all dimensions of length/width including diameters. This tolerance includes allowance for shrinkage, die sinking and die polishing variations. (The minimum should be plus or minus 0.8 mm or 0.03 in.)
UNITS OF MEASURE
3. Length/Width Tolerances, normally combined with tolerances for die wear are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

3.00

76.2

6.00

152.4

11.00

279.4


DIE WEAR TOLERANCES
SCOPE
1. Die wear varies according to the material that is forged and the shape of the forging. Consequently, Die Wear Tolerances for various materials are applied in addition to Length/Width Tolerances on dimensions pertaining to forged surfaces only. Die Wear Tolerances do not apply on centertocenter dimensions. (See example 4 ).
TOLERANCE
2. (a) Die Wear Tolerances for all length, width, and diameter dimensions under 750 mm or 30 in. are computed by multiplying the largest length or diameter (measured parallel to the fundamental parting line of the dies) by the appropriate factor in Table I below. Die Wear Tolerances for all length, width and diameter dimensions over 750 mm or 30 in. are taken directly from Table I.
(b) Die Wear Tolerances on external dimensions are expressed as plus values only. (See examples 5 and 6.) Die Wear Tolerances on internal dimensions are expressed as minus values only. (See examples 7 and 8.)
(c) Die Wear Tolerances per surface, on both external and internal dimensions are onehalf the computed amount.
NOTE:
Allowances for die wear occuring on dimensions measured perpendicular to the fundamental parting line of the dies are included in Die Closure Tolerances (Table II).
TABLE I: DIE WEAR TOLERANCES
Materials 
Under 30 in. or 750 mm Factor (in./inch) (mm/millimeter) 
Over 30 in. or 750 mm Constant 
in. 
mm 
Carbon, Low Alloys 
0.005 
0.15 
3.81 
Stainless 
0.007 
0.21 
5.33 
Heat Resistant Alloy 
0.009 
0.27 
6.86 
Titanium 
0.009 
0.27 
6.86 
Aluminum 
0.004 
0.12 
3.05 
Brass & Copper 
0.004 
0.12 
3.05 
UNITS OF MEASURE
3. Die Wear Tolerances combined with Length/Width Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or .01 in the inch system.
LIMITATIONS
4. The male portions of dies may, in special situations, tend to mushroom or upset rather than wear. In such cases, the requirements of the forging should be confirmed by purchaser and producer in advance of production.

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

0.07

1.8

0.09

2.3

3.00

76.2

6.00

152.4

11.00

279.4


COMPUTATION
MATERIAL: CARBON STEEL
(DIMENSIONS UNDER 30 IN. OR 750 mm)
EXAMPLE 1
(SEE FIGURE 2)

Tolerance on Length Dimension 

Plus 
Minus 

Length (mm) x Length/Width Tolerance factor 
= 279.4 x 0.003 = 
0.839 
0.839 
METRIC 
Length (mm) x Die Wear Tolerance factor 
= 279.4 x 0.005 = 
1.397 
___ 

(Table I) 

+2.236 
0.839 

Raised to the next highest 0.1mm 

+2.3 
0.9* 


Length x Length/Width Tolerance factor 
= 11 x 0.003 = 
0.033 
0.033 
INCH 
Length x Die Wear Tolerance factor 
= 11 x 0.005 = 
0.055 
___ 

(Table I)


+0.088 
0.033 

Raised to the next highest 0.01 in. 

+0.09 
0.04 
*Variance due to rounding
BACK TO TOP
EXAMPLE 2 (DIMENSIONS OVER 30 IN. OR 750 mm)
METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Length (mm) x Length/Width Tolerance factor 
= 
787.4 
x 
0.003 
= 
2.362 
2.362 

Length (mm) x Die Wear Tolerance factor 
= 
3.81 
x 
0.005 
= 
3.81 
  

(Table I) 





+6.172 
2.362 

Raised to the next highest 0.1mm 





+6.2 
2.4 


Length x Length/Width Tolerance factor 
= 
31 
x 
0.003 
= 
0.093 
0.093 
INCH 
Length x Die Wear Tolerance factor 
= 

x 
0.15 
= 
0.15 
  

(Table I)






+0.243 
0.093 

Raised to the next highest 0.01 in. 





+.25 
0.1 
EXAMPLE 3
(SEE FIGURE 2)
METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Length (mm) x Length/Width Tolerance factor 
= 
76.2 
x 
0.003 
= 
0.229 
0.229 

Greatest Length (mm) x Die Wear Tolerance factor 
= 
279.41 
x 
0.005 
= 
1.397 
  

(Table I) 





+1.626 
0.229 

Raised to the next highest 0.1mm 





+1.7 
0.3 

Minimum Tolerance 





.8 



Wide Length/Width Tolerance factor 
= 
3 
x 
0.003 
= 
0.009 
0.009 
INCH 
Greatest Length x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
0.55 
  

(Table I)






+0.064 
0.009 

Raised to the next highest 0.01 in. 





+.0.07 
0.01 

Minimum Tolerance 





0.03 

EXAMPLE 4
(SEE FIGURE 2)
<METRIC 
Tolerance on Length Dimension 





Plus 
Minus 
Dimension (mm) x Length/Width Tolerance factor 
= 
152.4 
x 
0.003 
= 
0.457 
0.457 

Raised to the next highest 0.1 mm 





+0.5 
0.5 

Minimum Tolerance 





+0.8 
0.8 


Dimension x Length/Width Tolerance factor 
= 
6 
x 
0.003 
= 
0.018 
0.018 
INCH 
Raised to the next highest 0.01 in. 
= 




+0.02 
0.02 

Minimum Tolerance 




+0.03 
0.03 

BACK TO TOP

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.04

1.1

0.07

1.8

0.09

2.3

4.00

101.6

11.00

279.4


COMPUTATION EXTERNAL DIMENSIONS
MATERIAL: CARBON STEEL
EXAMPLE 5 (SEE FIGURE 3)
METRIC 
Tolerance on External Dimension 





Plus 
Minus 
Diameter (mm) x Length/Width Tolerance factor 
= 
279.4 
x 
0.003 
= 
0.839 
0.839 

Diameter (mm) x Die Wear Tolerance factor 
= 
79.4 
x 
0.005 
= 
1.397 
  

(Table I) 





+2.2236 
0.839 

Raised to the next highest 0.1mm 





+2.3 
0.9* 


Diameter x Length/Width Tolerance factor 
= 
11 
x 
0.033 
= 
0.033 
0.033 
INCH 
Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.055 
= 
0.055 
  

(Table I)






+0.243 
0.033 

Raised to the next highest 0.01 in. 





+0.09 
0.04 
EXAMPLE 6 (SEE FIGURE 3)
METRIC 
Tolerance on External Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
101.6 
x 
0.003 
= 
0.305 
0.305 

Largest Diameter x Die Wear Tolerance factor (Table I) 
= 
279.4 
x 
0.005 
= 
1.397 
  







+1.702 
0.3 

Raised to the next highest 0.1mm 





+1.8 


Minimum Tolerance 





+0.8 



Diameter x Length/Width Tolerance factor 
= 
4 
x 
0.033 
= 
0.012 
0.012 
INCH 
Largest Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
0.055 
  

(Table I)






+0.067 
0.012 

Raised to the next highest 0.01 in. 





+0.07 
0.02 

Minimum Tolerance 





0.03 

BACK TO TOP

METRIC CONVERSION 
INCH 
mm 
0.03

0.8

0.07

1.8

0.09

2.3

2.00

50.8

9.00

228.6


COMPUTATION EXTERNAL DIMENSIONS
MATERIAL: CARBON STEEL
EXAMPLE 7 (SEE FIGURE 4)
METRIC 
Tolerance on Internal Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
228.6 
x 
0.003 
= 
0.686 
0.686 

Largest Diameter (mm) x Die Wear Tolerance factor 
= 
279.4 
x 
0.005 
= 
— — 
1.397 

(Table I) 





+0.686 
2083 

Raised to the next highest 0.1mm 





+0.07 
2.1 

Minimum Tolerance 




+0.8 




Diameter x Length/Width Tolerance factor 
= 
9 
x 
0.033 
= 
0.027 
0.033 
INCH 
Diameter x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
— — 
0.055 

(Table I)






+0.027 
0.082 

Raised to the next highest 0.01 in. 





+0.03 
0.09 
EXAMPLE 8 (SEE FIGURE 4)
METRIC 
Tolerance on Internal Dimension 





Plus 
Minus 
Diameter x Length/Width Tolerance factor 
= 
50.8 
x 
0.003 
= 
0.152 
0.152 

Largest Diameter x Die Wear Tolerance factor (Table I) 
= 
279.4 
x 
0.005 
= 
— — 
1.397 







+0.152 
1.549 

Raised to the next highest 0.1mm 





+0.2 
1.6 

Minimum Tolerance 




+0.8 




Diameter x Length/Width Tolerance factor 
= 
2 
x 
0.003 
= 
0.006 
0.006 
INCH 
Largest Length x Die Wear Tolerance factor 
= 
11 
x 
0.005 
= 
— — 
0.055 

(Table I)






+0.006 
0.061 

Raised to the next highest 0.01 in. 





+0.01 
0.07 

Minimum Tolerance 




+0.03 


BACK TO TOP
DIE CLOSURE TOLERANCES
SCOPE
1. Die Closure Tolerances relate to variations in thickness of forgings as affected by the closing of the dies and die wear, and pertain to variations in dimensions crossing the fundamental parting line.
TOLERANCE
2. Die Closure Tolerances on forgings are based on the projected area of the forging at the trim line, not including flash, but including all areas to be subsequently punched out, and are applied as plus tolerances only. See Table II, below.
TABLE II: DIE CLOSURE TOLERANCES
TABULATED FIGURES ARE PLUS VALUES ONLY


Area at the Trim Line Flash not included, expressed in square millimeters

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
1.1 
1.6 
2.3 
3.3 
4.1 
4.9 
6.4 
Stainless 
1.6 
2.3 
3.4 
4.1 
4.9 
6.4 
7.9 
Heat Resistant Alloy 
1.6 
2.3 
3.4 
4.9 
6.4 
7.9 
9.7 
Titanium 
1.6 
2.3 
3.4 
4.9 
6.4 
7.9 
9.7 
Aluminum 
1.1 
1.3 
1.8 
2.3 
3.4 
4.9 
6.4 
Brass & Copper 
1.1 
1.3 
1.8 
2.3 
3.4 
4.9 
6.4 


Area at the Trim Line Flash not included, expressed in square inches

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
0.04 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Stainless 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
0.31 
Heat Resistant Alloy 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Titanium 
0.06 
0.09 
0.13 
0.25 
0.25 
0.31 
0.38 
Aluminum 
0.04 
0.05 
0.07 
0.13 
0.13 
0.19 
0.25 
Brass Copper 
0.04 
0.05 
0.07 
1.13 
0.13 
0.19 
0.25 
BACK TO TOP
UNITS OF MEASURE
3 .
Die Closure Tolerances are expressed decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.13 
3.4 
2.00 
50.8 

MATCH TOLERANCES
SCOPE
1. (a) Match Tolerances relate to displacement of a point in one diehalf from the corresponding point in the opposite diehalf in any direction parallel to the fundamental parting line of the dies. (Values from Table III must be doubled when specified as F.I.R. or T.I.R.)
(b) Match Tolerances are applied separately and independently to all other tolerances. Where possible, measurements are made at areas of the forging unaffected by die wear.
TOLERANCE
2. Match Tolerances are based on weight of the forging after trimming and are expressed as decimal inch or decimal millimeters according to Table III, below.
MEASURING FOR MATCH TOLERANCES
3 . In cases where measurements for determining match tolerances must be made from surfaces of the forging where uneven wearing of the dies has caused surplus stock, accuracy depends on making the proper allowances for these wearcaused surpluses, and eliminating their influence from the computation.
UNITS OF MEASURE
4. Match Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.
TABLE III: MATCH TOLERANCES


Weights of Forgings after Trimming, in Pounds

METRIC 
Materials 
0 to 2.5 
Over 2.5 to 12.5 
Over 12.5 to 25 
Over 25 to 50 
Over 50 to 100 
Over 100 to 250 
Over 250 to 500 
Over 500 
Carbon, Low Alloys 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
300, 400 Stainless Steels 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Heat Resistant Alloy 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Titanium 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
6.4 
Aluminum 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 
Brass & Copper 
0.5 
0.8 
1.2 
1.6 
2.4 
3.2 
4.0 
4.8 


Weights of Forgings after Trimming, in Pounds

INCH 
Materials 
0 to 5 
Over 5 to 25 
Over 25 to 50 
Over 50 to 100 
Over 100 to 200 
Over 200 to 500 
Over 500 to 1000 
Over 1000 
Carbon, Low Alloys 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
300, 400 Stainless Steels 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Heat Resistant Alloy 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Titanium 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Aluminum 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
Brass & Copper 
0.02 
0.03 
0.05 
0.06 
0.09 
0.13 
0.16 
0.19 
Formula refers to Figure 6
D = Match Tolerance or displacement
A = Projected maximum overall dimensions measured parallel to the main parting line of the dies.
B = Projected minimum overall dimensions measured parallel to the main parting line of the dies.


AB 
NOTE: F.I.R. or T.I.R. or AB = 2D D= 
2 

BACK TO TOP
RADII TOLERANCES
SCOPE
1. Radii Tolerances relate to all fillet radii and corner radii.
TOLERANCES
2. Radii Tolerances are plus or minus onehalf the specified radii, except where corner radii are affected by subsequent removal of draft by trimming, broaching or punching. If draft is removed as result of trimming, broaching or punching, the minus radius tolerance (0.5 of specified radius) is commonly modified to allow a square corner to be formed. (See Figures 8 and Example 10.)
UNITS OF MEASURE
3.
Radii Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.06 
1.6 
0.07 
18 
0.13 
3.4 
0.025 
6.4 

COMPUTATION
EXAMPLE 9
(SEE FIGURE 7)
METRIC 
3.4 mm radius is specified 




Max radius 
= 
1.5 x 3.4 mm 
= 
5.1. mm radius 
Min radius 
= 
0.5 x 2.4 mm 
= 
1.7 mm radius 

6.4 mm radius is specified 




Max radius 
= 
1.5 x 6.4 mm 
= 
9.4 mm radius 
Min radius 
= 
0.5 x 6.4 mm 
= 
3.2 radius 
BACK TO TOP
EXAMPLE 9 (continued)
(SEE FIGURE 7)
INCH 
0.13 in. radius is specified 




Max radius 
= 
1.5 x 0.13 in 
= 
0.195 in. radius 
Raised to the next highest 

0.01in 
= 
1.7 mm radius 
Min radius 
= 
0.5 x 0.13 in 
= 
0.065 in. radius 

Raised to the next highest 0.01 in 


= 
0.07 in. radius 

0.25 mm radius is specified 




Max. radius 
= 
1.5 x 0.25 in 

0.375 in. radius 
Raised to the next highest 

0.01 in 
= 
0.38 in. radius 
Min radius 
= 
0.5 x 0.25 in 
= 
0.13 in radius 

METRIC CONVERSION

INCH 
mm 
0.13 
34 

EXAMPLE 10
(SEE FIGURE 8)
METRIC 
3.4 mm radius is specified 




Max radius 
= 
1.5 x 3.4 mm 
= 
5.1. mm radius 
Min radius = 0 mm 





INCH 
0.13 mm radius is specified 




Max radius 
= 
1.5 x 6.4 mm 
= 
9.4 mm radius 
Min radius = 0 in. 


= 

BACK TO TOP
EXTREMITY TOLERANCES
SCOPE
1. Extremity Tolerances relate to variations in height of protrusions (steps) which are perpendicular to the fundamental parting line and are independent of die closure, die wear and other factors dealt with in this book. This tolerance applies only to steps that are contained in one die.
TOLERANCE
2. Tolerances on extremities are determined by taking the step dimension times ±0.005 inch per inch or millimeter per millimeter. This tolerance includes allowances for: nonfill, shrinkage, die sinking, polishing variations, and special die wear considerations. This tolerance is in addition to the Die Closure Tolerance. Minimum tolerance should be ±0.8 mm or 0.03 in.
UNITS OF MEASURE
3. Extremity Tolerances are expressed as decimal millimeter in units of 0.1 mm or greater and expressed as decimal inch, in units of 0.01 or greater. Decimals used in computing tolerances are totaled and raided to the next highest 0.1 in the metric system or 0.01 in the inch system.

METRIC CONVERSION

INCH 
mm 
0.03 
0.8 
0.06 
1.6 
1.00 
25.4 
12.00 
304.8 

EXAMPLE 11
FORGINGS HAVING PERPENDICULAR EXTREMETIES
METRIC 


Plus 
Minus 
Extremity Tolerance (±0.005 mm per millimeter) for the 305 mm step dimension 
305 x 0.005 = 
1.525 
1.525 
Raised to the next highest 0.1mm 

+1.6 
1.6 

INCH 
Extremity Tolerance (±0.005 in. per inch) for the 12 in. step dimension 




12 x 0.005 = 
+0.060 
0.060 
Min radius = 0 in. 



BACK TO TOP
FLASH EXTENSION TOLERANCES
SCOPE
1. Flash Extension Tolerances are based on weight of the forging after trimming, and related to the amount of flash extension. Flash is measured from the body of the forging to the trimmed edge of the flash.
TOLERANCES
2. Flash Extension Tolerances are expressed in inches or millimeters according to Table IV below.
UNITS OF MEASURE
3. Flash Extension Tolerances are expressed as decimal inch, in units of 0.01 or greater and expressed as decimal millimeter in units of 0.1 mm or greater.
TABLE IV


Materials

METRIC 
Weights of Forgings After Trimming, in kilograms 
Carbon Low Alloy & Aluminum 
Stainless Heat Resistant Alloys & Titanium 
Brass 7 Copper 
5 and under 
0 to 0.8 
0 to 1.6 
0 to 0.8 
Over 5 to 10 incl. 
0 to 1.6 
0 to 2.3 
0 to 1.6 
Over 10 to 25 incl. 
0 to 2.3 
0 to 3.3 
0 to 2.3 
Over 25 to 50 incl. 
0 to 3.3 
0 to 4.9 
0 to 3.3 
Over 50 to 100 incl. 
0 to 4.9 
0 to 6.4 
0 to 4.9 
Over 100 to 250 incl. 
0 to 6.4 
0 to 7.9 
0 to 6.4 

Over 250 to 500 incl. 
0 to 7.9 
0 to 9.7 
0 to 7.9 

Over 500 
0 to 9.7 
0 to 12.7 
0 to 9.7 
BACK TO TOP
TABLE IV (Continued)


Materials

METRIC 
Weights of Forgings After Trimming, in kilograms 
Carbon Low Alloy & Aluminum 
Stainless Heat Resistant Alloys & Titanium 
Brass & Copper 
5 and under 
0 to 0.03 
0 to 0.06 
0 to 0.03 
Over 5 to 25 incl. 
0 to 0.06 
0 to 0.09 
0 to 0.06 
Over 25 to 50 incl. 
0 to 0.09 
0 to 0.13 
0 to 0.09 
Over 50 to 100 incl. 
0 to 0.13 
0 to 0.19 
0 to 0.13 
Over 100 to 200 incl. 
0 to 0.19 
0 to 0.25 
0 to 0.19 
Over 200 to 500 incl. 
0 to 0.25 
0 to 0.31 
0 to 0.25 

Over 500 to 1000 incl. 
0 to 0.31 
0 to 0.38 
0 to 0.31 

Over 1000 
0 to 0.38 
0 to 0.50 
0 to 0.38 
STRAIGHTNESS TOLERANCES
SCOPE
1. (a) Straightness Tolerances relate to deviations of surfaces and centerlines from the specified contour. Straightness Tolerances are applied independently of, and in addition to, all other tolerances.
(b) Four general classes of shapes have been selected for guidelines in choosing appropriate Straightness Tolerances.
CLASSES OF SHAPES
Class 
Shape of Forging 
Examples 
A 
A Elongated Length dimension greater than width or height 
long connecting rods, shafts, levers, etc. 
B 
Flat and thin 
disc, plates, etc. 
C 
Flat and thin with protrusion at right angles to the parting line 
wear plates, crawler track shoes 
D 
Blocktype forgings with neither length, width. nor thickness being predominant 
pump or valve bodies steam chests, etc. 
UNITS OF MEASURE
2. 

Straightness Tolerances are expressed as decimal inch, in units of 0.01 or greater and expressed as decimal millimeter in units of 0.1 mm or greater. Decimals used in computing tolerances are totaled and raised to the next highest 0.01 in the inch system or 0.1 in the metric system.

BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS
3. 
(a) 
CLASS A Shapes (Elongated _ Length dimensions greater than width or height) Tolerance: 0.003 in. per inch or mm per millimeter of the greatest dimension. 

METRIC CONVERSION

INCH 
mm 
0.04 
1.1 
11.0 
279.4 

EXAMPLE 12
(SEE FIGURE 11)
METRIC 
Greatest dimension x Straightness Tolerance 
279.4 x 0.003 = 
0.84 
Raised to the next highest 0.1 mm 

0.9 
Straightness Tolerance for CLASS A Shape in Figure 11 

0.9 

From true center lines in any plane 

INCH 
Greatest dimension x Straightness Tolerant 
11 x 0.003 = 
0.033 
Raised to the next highest 0.01 in. 

0.04 
Straightness Tolerance for CLASS A Shape in Figure 11 

0.04 

From true center lines in any plane 


BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS (continued)
(b) Class B Shapes (flat and thin)
Tolerance: Straightness Tolerance for CLASS B Shapes as shown in Table V.
TABLE V: STRAIGHTNESS TOLERANCES


Area at the Trim Line Flash not included, expressed in square millimeters

METRIC 
Materials 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
Carbon, Low Alloys 
0.9 
1.6 
2.3 
3.3 
4.1 
4.9 
6.4 
Stainless 
1.6 
2.3 
3.3 
4.1 
4.8 
6.4 
7.9 
Heat Resistant Alloy 
1.6 
2.3 
3.3 
4.8 
6.4 
7.9 
9.7 
Titanium 
1.6 
2.3 
3.3 
4.8 
6.4 
7.9 
9.7 
Aluminum 
0.8 
0.8 
1.5 
2.3 
3.3 
4.8 
6.4 
Brass & Copper 
0.8 
0.8 
2.5 
2.3 
3.3 
4.8 
6.4 


Area at the Trim Line Flash not included, expressed in square millimeters

INCH 
Materials 
10 and under 
Over 10 to 30 incl. 
Over 30 to 50 incl. 
Over 50 to 100 incl. 
Over 100 to 50 incl. 
Over 500 to 1000 incl. 
Over 1000 
Carbon, Low Alloys 
0.04 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
Stainless 
0.06 
0.09 
0.13 
0.16 
0.19 
0.25 
0.31 
Heat Resistant Alloy 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Titanium 
0.06 
0.09 
0.13 
0.19 
0.25 
0.31 
0.38 
Aluminum 
0.04 
0.05 
0.07 
0.09 
0.13 
0.19 
0.25 
Brass & Copper 
0.04 
0.05 
0.07 
0.09 
0.13 
0.19 
0.25 
BACK TO TOP

METRIC CONVERSION

INCH 
mm 
0.19 
4.9 
30.00 
762.0 
707.00 
456,038.0 

EXAMPLE 13
(SEE FIGURE 12 and 13)
METRIC 
Computed area at Trim Line 
456,038 sq. mm 
Appropriate value from Table V 
4.9 mm 
Straightness Tolerance for CLASS B Shape in Figures 12 and 13 
4.9 mm 


From the highest to lowest point of contour 
INCH 
Computed area at Trim Line 
707 Sq.in, 
Appropriate value from Table V 
0.19 in. 
Straightness Tolerance for CLASS B Shape in Figures 12 and 13 
0.19 in. 


From the highest to lowest point of contour 
BACK TO TOP
STRAIGHTNESS TOLERANCES
TOLERANCES AND APPLICATIONS (continued)
(c) CLASS C Shapes (flat and thin with protrusion at right angles to the parting line)
Tolerance: The Straightness Tolerance on the flat portion of CLASS C Shapes is computed first. It is considered separately from the tolerance on the protruding portion and is determined in an identical manner as for CLASS B Shapes using Table V. The Straightness Tolerance on a protrusion is 0.003 in. per inch or mm per millimeter.

METRIC CONVERSION

INCH 
mm 
0.04 
1.1 
0.19 
4.9 
12.00 
304.8 
30.00 
762.0 

EXAMPLE 14
(SEE FIGURE 14)
METRIC 
Material: Carbon Steel 
= 
456,038 sq. mm 
The Tolerance on flat portion is computed first: 
= 
4.9 mm 
Computed area at Trim Line 
= 
4.9 mm 
Appropriate value from Table V 

Straightness Tolerance applied to flat portion 



From the highest to lowest point of contour 
INCH 
Computed area at Trim Line 
= 
707 Sq. In. 
Appropriate value from Table V 
= 
0.19 in. 
Straightness Tolerance applied to flat portion 
= 
0.19 in. 


From the highest to lowest point of contour 
BACK TO TOP
EXAMPLE 15
METRIC 
The Protrusion is checked against a line perpendicular to the plane established for checking the flat portion: 
Protrusion x Straightness 
Tolerance = 304.8 x 0.003 
= 
0.91 
Raised to the next highest 0.1 mm 
= 
1.0 

From true center lines in any plane 

INCH 
Protrusion x Straightness 


Tolerance = 12 in. x 0.003 
= 
0.036 
Raised to the next highest 0.01 in. 
= 
0.04 

From true center lines in any plane 

(d) 
CLASS D SHAPES (blocktype forgings with neither length, width nor thickness being predominant) 





Tolerance: Where tolerances are desired, agreement between purchaser and forging producer is normally reached before production proceeds.

DRAFT ANGLE TOLERANCES
SCOPE
1. 

Draft Angle Tolerances apply to all draft angles, specified on drawings that are not affected by subsequent operations. 
TOLERANCE
2. 

Draft Angle Tolerances are +2°0° unless modified by prior agreement between purchaser and producer. 

EXAMPLE 15
METRIC 
The Protrusion is checked against a line perpendicular to the plane established for checking the flat portion: 
Protrusion x Straightness 
Tolerance = 304.8 x 0.003 
= 
0.91 
Raised to the next highest 0.1 mm 
= 
1.0 

From true center lines in any plane 

INCH 
Protrusion x Straightness 


Tolerance = 12 in. x 0.003 
= 
0.036 
Raised to the next highest 0.01 in. 
= 
0.04 

From true center lines in any plane 

(d) 
CLASS D SHAPES (blocktype forgings with neither length, width nor thickness being predominant) 





Tolerance: Where tolerances are desired, agreement between purchaser and forging producer is normally reached before production proceeds.

DRAFT ANGLE TOLERANCES
SCOPE
1. 

Draft Angle Tolerances apply to all draft angles, specified on drawings that are not affected by subsequent operations. 
TOLERANCE
2. 

Draft Angle Tolerances are +2°0° unless modified by prior agreement between purchaser and producer. 

BACK TO TOP
SURFACE TOLERANCES
SCOPE
1. 

Surface Tolerances relate to depth of dressouts, scale pits and other imperfections on the surface of forgings. 
TOLERANCES AND CONDITIONS
2. 
(a) 
Dressouts, scale pits and other imperfections are commonly allowed on surfaces to be finish machined unless purchaser\'s specification or drawing states otherwise. Where purchaser specified stock for machining, these imperfections are commonly permitted to within 1.6 mm or 0.06 in. of the finished surface or to within one half of the stock allowance, whichever is smaller. . 




(b) 
Where surfaces of forgings are intended for use in "as forged" condition, surface imperfections are commonly permitted as shown in Table VI. 
METRIC 
Area at the Trim Line Flash not included, expressed in square millimeters 
0 to 6.5 x 1000 
Over 6.5 to 20 x 1000 
Over 20 to 32 x 1000 
Over 32 to 65 x 1000 
Over 65 to 300 x 1000 
Over 300 to 650 x 1000 
Over 650 x 1000 
0.8 
1.2 
1.7 
2.1 
2.5 
3.2 
4.0 
METRIC 
Area at the Trim Line Flash not included, expressed in square inches 
Over 10 to 30 incl. 
Over 10 to 30 incl. 
Over 30 to 50 incl. 
Over 50 to 100 incl. 
Over 100 to 500 incl. 
Over 500 to 100 incl. 
Over Over 100 
0.03 
0.05 
0.07 
0.08 
0.10 
0.13 
0.16 

BACK TO TOP
FINISH ALLOWANCES FOR MACHINING
(For the purpose of designing a forging)
Finish allowance refers to the amount of material that is to be machined from the forging to obtain the finished part. Forging dimensions are commonly analyzed independently, with consideration given to all applicable tolerances including match, straightness, length and width but not including die wear.
TABLE VII: FINISH ALLOWANCES
Greatest Dimension 
Minimum Finish Stock Per Surface 
Over 
But Not Over 
in 
mm 
in 
mm 
in 
mm 
 
 
8 
203 
0.06 
1.6 
8 
203 
16 
406 
0.09 
2.4 
16 
406 
24 
610 
0.13 
3.2 
24 
610 
31 
914 
0.16 
4.0 
36 
916 
 
 
0.19 
4.8 
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