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Hex Keys (Excerpt from JIS B 4648 2008)

Last updated:18 June 2019

Width across
flats　s　mm 		Diagonal distance　e　mm Length of long shaft
　ℓ 1　mm 		Length of short shaft　ℓ 2　mm Minimum Rockwell hardness　HRC Minimum guaranteed torque Md　N・m
Nominal dia. Max. Min. Max. Min. Standard type M type L type Tolerance Standard dimension Tolerance
0.7 0.71 0.70 0.79 0.76 33 - - 0
-2 		7 0
-2 		52 0.08
0.9 0.89 0.88 0.99 0.96 33 - - 0
-2 		11 0
-2 		52 0.18
1.3 1.27 1.24 1.42 1.37 41 63.5 81 0
-2 		13 0
-2 		52 0.53
1.5 1.50 1.48 1.68 1.63(b) 46.5 63.5 91.5 0
-2 		15.5 0
-2 		52 0.82
2 2.00 1.96 2.25 2.18(c) 52 77 102 0
-2 		18 0
-2 		52 1.9
2.5 2.50 2.46 2.82 2.75(c) 58.5 87.5 114.5 0
-4 		20.5 0
-2 		52 3.8
3 3.00 2.96 3.39 3.31(c) 66 93 129 0
-4 		23 0
-2 		52 6.6
4 4.00 3.95 4.53 4.44(c) 74 104 144 0
-4 		29 0
-2 		52 16
5 5.00 4.95 5.67 5.58(d) 85 120 165 0
-4 		33 0
-2 		52 30
6 6.00 5.95 6.81 6.71(d) 96 141 186 0
-6 		38 0
-2 		52 52
8 8.00 7.94 9.09 8.97 108 158 208 0
-6 		44 0
-2 		52 120
10 10.00 9.94 11.37 11.23 122 180 234 0
-6 		50 0
-2 		48 220
12 12.00 11.89 13.65 13.44 137 202 262 0
-6 		57 0
-2 		48 370
14 14.00 13.89 15.93 15.70 154 229 294 0
-7 		70 0
-3 		48 590
17 17.00 16.89 19.35 19.09 177 262 337 0
-7 		80 0
-3 		45 980
19 19.00 18.87 21.63 21.32 199 - - 0
-7 		89 0
-3 		45 1360
22 22.00 21.87 25.05 24.71 222 - - 0
-12 		102 0
-5 		45 2110
24 24.00 23.87 27.33 26.97 248 - - 0
-12 		114 0
-5 		45 2750
27 27.00 26.87 30.75 30.36 277 - - 0
-12 		127 0
-5 		45 3910
32 32.00 31.84 36.45 35.98 347 - - 0
-12 		157 0
-5 		45 4000
36 36.00 35.84 41.01 40.50 391 - - 0
-12 		176 0
-5 		45 4000
41 41.00 40.84 46.71 46.15 435 - - 0
-12 		195 0
-5 		45 4000
46 46.00 45.84 52.41 51.80 480 - - 0
-12 		215 0
-5 		45 4000
・e max = 1.14 s max − 0.03(1.5 ≦ s ≦ 46)
・e min = 1.13 s min (8 ≦ s ≦ 46)
・ (b) e min = 1.13 s min − 0.04
・ (c) e min = 1.13 s min − 0.03
・ (d) e min = 1.13 s min − 0.02
・ The spanner should be hardened across its entire length and through to its center.
・ Md where s = 27 mm or lower is calculated by Md = 0.85 (0.7Rm) (0.224 5s3). However, Rm is a tensile
strength approximated from the spanner’s minimum Rockwell hardness.

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