Machinery's Handbook, 31st Edition
2544
Metric Keys and Keyways Metric Square And Rectangular Keys and Keyways: Width Tolerances and Deviations Greater than Basic Size
This ANSI/ASME B18.25.3M standard covers requirements for square and rectangular parallel keys and keyways intended for both alignment of shafts and hubs, and transmit- ting torque between shafts and hubs. Keys covered by this standard have a relatively loose width tolerance. All width tolerances are positive. Keys with minus width tolerances and a smaller tolerance range are covered by ANSI/ASME B18.25.1M-1996 (Withdrawn). Dimensions and tolerances for square and rectangular keys are shown in Table 3. Recom- mended dimensions and tolerances for keyways are shown in Table 4. All dimensions in this standard are in millimeters.
Table 3. Dimensions and Tolerances for Metric Square and Rectangular Parallel Keys ANSI/ASME B18.25.3M-2003 Width Tolerances and Deviations Greater than Basic Size Width, b Thickness, h Chamfer or Radius, s
Range of Lengths From To a
Basic Size Tolerance Basic Size Tolerance Min.
Max.
Square Keys
2 3 4 5 6 5 6
2 3 4 5 6 3 4 5 7 6 8 6 8 6 9 7
20 36 45 56 70 56 70
+0.040 − 0.000 +0.045 − 0.000
+0.040 − 0.000 +0.045 − 0.000 +0.160 − 0.000 +0.175 − 0.000 +0.190 − 0.000 +0.175 − 0.000 +0.19 − 0.000 +0.175 − 0.000 +0.190 − 0.000 +0.175 − 0.000 +0.190 − 0.000 +0.210 − 0.000 +0.190 − 0.000 +0.210 − 0.000
6 8
0.16
0.25
10 14
0.25
0.40
Rectangular Keys
10 14
+0.045 − 0.000
0.25
0.40
8
18
90
+0.050 − 0.000
10
0.40
0.60
22
110
12
28
140
14
36
160
+0.075 − 0.000
0.40
0.60
45
180
16
10 7 11
18
50 56 63
200
8
+0.050 − 0.033
20
0.60
0.80
12
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