Gagemakers Tolerances Machinery's Handbook, 31st Edition
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Table 6. American National Standard Gagemakers Tolerances ANSI B4.4M-1981 (Withdrawn)
Gagemakers Tolerance
Workpiece Tolerance
IT Grade
ISO Symbol a
Recommended Gage Usage
Class
Low-precision gages recommended to be used to inspect workpieces held to internal (hole) tolerances C11 and H11 and to external (shaft) tolerances c11 and h11.
ZM 0.05 IT11 IT11
YM 0.05 IT9 IT9 Gages recommended to be used to inspect workpieces held to internal (hole) tolerances D9 and H9 and to external (shaft) tolerances d9 and h9. XM 0.05 IT8 IT8 Precision gages recommended to be used to inspect workpieces held to internal (hole) tolerances F8 and H8. XXM 0.05 IT7 IT7 Recommended to be used for gages to inspect workpieces held to internal (hole) tolerances G7, H7, K7, N7, P7, S7, and U7, and to external (shaft) tolerances f7 and h7. XXXM 0.05 IT6 IT6 High-precision gages recommended to be used to inspect workpieces held to external (shaft) tolerances g6, h6, k6, n6, p6, s6, and u6. a Gagemakers tolerance is equal to 5 percent of workpiece tolerance or 5 percent of applicable IT grade value. See Table 7. For workpiece tolerance class values, see previous Table 2 through Table 5, inclusive. Table 7. American National Standard Gagemakers Tolerances ANSI B4.4M-1981 (Withdrawn) Basic Size Class ZM Class YM Class XM Class XXM Class XXXM Over To 0.05 IT11 0.05 IT9 0.05 IT8 0.05 IT7 0.05 IT6 0 3 0.0030 0.0012 0.0007 0.0005 0.0003 3 6 0.0037 0.0015 0.0009 0.0006 0.0004 6 10 0.0045 0.0018 0.0011 0.0007 0.0005 10 18 0.0055 0.0021 0.0013 0.0009 0.0006 18 30 0.0065 0.0026 0.0016 0.0010 0.0007 30 50 0.0080 0.0031 0.0019 0.0012 0.0008 50 80 0.0095 0.0037 0.0023 0.0015 0.0010 80 120 0.0110 0.0043 0.0027 0.0017 0.0011 120 180 0.0125 0.0050 0.0031 0.0020 0.0013 180 250 0.0145 0.0057 0.0036 0.0023 0.0015 250 315 0.0160 0.0065 0.0040 0.0026 0.0016 315 400 0.0180 0.0070 0.0044 0.0028 0.0018 400 500 0.0200 0.0077 0.0048 0.0031 0.0020 All dimensions are in millimeters. For closer gagemakers tolerance classes than Class XXXM, specify 5 percent of IT5, IT4, or IT3 and use the designation 0.05 IT5, 0.05 IT4, etc.
Min. (GO) size Gagemakers Tolerance Normal Workpiece Distribution Curve
Max. (GO) size Workpiece Tolerance
Min. (GO) size Gagemakers Tolerance Wear Allowance
Workpiece Tolerance
Gagemakers Tolerance Wear Allowance
Internal Dimensions (holes)
External Dimensions (holes)
Fig. 4. Relationship between Gagemakers Tolerance, Wear Allowance and Workpiece Tolerance
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