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SOCKET CAP,
SHOULDER, AND SET SCREWS,
HEX AND SPLINE KEYS (INCH SERIES)
ASME B18.3-1998 |
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TABLE 8 DIMENSIONS OF HEXAGON KEYS AND BITS
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Nominal Key or
Bit and
Socket Size |
Hexagon Width
Across Flats
W |
Hexagon Width
Across Corners
Y
[Note (2)] |
Length of
Short Arm
B |
Length of Long
Arm
C |
Minimum
Radius
of Bend
R |
Length
of Bit,
+0.062
L
[Note (3)] |
Maximum
Chamfer,
K
[Note (4)] |
|
Short Series |
Long Series |
|
Max. |
Min. |
Max. |
Min. |
Max. |
Min. |
Max. |
Min. |
Max. |
Min. |
|
...
...
...
1/16 |
0.028
0.035
0.050
0.062 |
0.0280
0.0350
0.0500
0.0625 |
0.0275
0.0345
0.0490
0.0615 |
0.0314
0.0393
0.0560
0.0701 |
0.0300
0.0378
0.0540
0.0680 |
0.312
0.438
0.625
0.656 |
0.125
0.250
0.438
0.469 |
1.312
1.312
1.750
1.844 |
1.125
1.125
1.562
1.656 |
2.688
2.766
2.938
3.094 |
2.500
2.578
2.750
2.906 |
0.062
0.062
0.062
0.062 |
...
...
...
... |
0.003
0.004
0.006
0.008 |
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5/64
3/32
7/64
1/8 |
0.078
0.094
0.109
0.125 |
0.0781
0.0937
0.1094
0.1250 |
0.0771
0.0927
0.1079
0.1235 |
0.0880
0.1058
0.1238
0.1418 |
0.0859
0.1035
0.1210
0.1390 |
0.703
0.750
0.797
0.844 |
0.516
0.562
0.609
0.656 |
1.969
2.094
2.219
2.344 |
1.781
1.906
2.031
2.156 |
3.281
3.469
3.656
3.844 |
3.094
3.281
3.469
3.656 |
0.078
0.094
0.109
0.125 |
...
...
...
... |
0.008
0.009
0.014
0.015 |
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9/64
5/32
3/16
7/32 |
0.141
0.156
0.188
0.219 |
0.1406
0.1562
0.1875
0.2187 |
0.1391
0.1547
0.1860
0.2172 |
0.1593
0.1774
0.2135
0.2490 |
0.1566
0.1745
0.2105
0.2460 |
0.891
0.938
1.031
1.125 |
0.703
0.750
0.844
0.938 |
2.469
2.594
2.844
3.094 |
2.281
2.406
2.656
2.906 |
4.031
4.219
4.594
4.969 |
3.844
4.031
4.406
4.781 |
0.141
0.156
0.188
0.219 |
...
...
...
... |
0.016
0.016
0.022
0.024 |
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1/4
5/16 |
0.250
0.312 |
0.2500
0.3125 |
0.2485
0.3110 |
0.2845
0.3570 |
0.2815
0.3531 |
1.219
1.344 |
1.031
1.156 |
3.344
3.844 |
3.156
3,656 |
5.344
6.094 |
5.156
5.906 |
0.250
0.312 |
...
... |
0.030
0.032 |
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Cam-Tech Industries uses up to 5/16" key
only. |
GENERAL NOTE: For
additional requirements refer to notes (4) THROUGH (6).
NOTES:
(1) Hexagon Keys are furnished as Short Arm Series or Long Arm Series.
(2) Any truncation or rounding of hexagon comers within the specified
across-corner dimensions shall be evident on all corners.
(3) For nominal socket sizes above 1 in., it is recommended that bits be
used in conjunction with standard hexagon wrenches or power drives. When the
application makes the use of keys necessary, the keys should conform to the
dimensions listed. Bits 1 in. and smaller are available, but the lengths
have not been standardized.
(4) Each end shall be square with the axis of each arm within 4 deg and
edges may be sharp or chamfered at the option of the manufacturer. The
chamfer shall not exceed the values listed.
(5) Material (Steel Alloy). Hexagon keys and bits shall be fabricated
from an alloy steel having two or more of the following alloying elements:
chromium, nickel, molybdenum, or vanadium, in sufficient quantity to ensure
that the specified minimum hardness of 48 HRC at the surface for nominal
sizes up to and including 3/8 in., and 45 HRC for nominal sizes over 3/8
in., is met when hexagon keys and bits are hardened by quenching from the
austenitizing temperature and tempered.
(6) For plated hexagon keys and bits, all dimensions are before plating.
Because of the high hardness of these products, it is recommended that they
not be electroplated.
(7) For applicability of keys and bits to various socket screw types and
sizes, see Nonmandatory Appendix B, Table B-1.
(8) Designation. To promote uniformity and understanding in communications
relating to products conforming to this Standard, it is recommended that
Hexagon Keys or Bits be designated in accordance with the following data,
preferably in the sequence shown: (a) product name (b) designation of the
standard (c) nominal key or bit size (d) series (e) protective finish, if
required
EXAMPLES:
Hexagon Key, ASME B18.3, '/, Short Arm Series
Hexagon Key, ASME B18.3, 1/8 Long Arm Series, Nickel Plated. [See Note (6).]
Hexagon Key Bit, ASME B18.3, 11/2 Hex
Reprinted from ASME
B18.3-2003, by permission of The American Society of Mechanical Engineers.
All rights reserved.
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