Inch series · controlled reference
Slotted Hex Head Machine Screw Dimensions
Complete nominal-size data from U.S. DoD military standard MS51849A for steel, slotted hex-head machine screws. Both UNF-2A and UNC-2A thread pitches are shown for every nominal size in the sheet.
Source: U.S. DoD MS51849A, Table I; the DoD record remains active and was validated in April 2026.
| Nominal size | Thread pitches | A — flats max / min | H — head height max / min | J — slot width max / min | T — slot depth max / min |
|---|---|---|---|---|---|
| #4 · 0.112 in | 48 UNF / 40 UNC | 0.187 / 0.181 | 0.060 / 0.049 | 0.039 / 0.031 | 0.036 / 0.023 |
| #6 · 0.138 in | 40 UNF / 32 UNC | 0.250 / 0.244 | 0.093 / 0.080 | 0.048 / 0.039 | 0.046 / 0.033 |
| #8 · 0.164 in | 36 UNF / 32 UNC | 0.250 / 0.244 | 0.110 / 0.096 | 0.054 / 0.045 | 0.066 / 0.052 |
| #10 · 0.190 in | 32 UNF / 24 UNC | 0.312 / 0.305 | 0.120 / 0.105 | 0.060 / 0.050 | 0.072 / 0.057 |
| 1/4 in | 28 UNF / 20 UNC | 0.375 / 0.367 | 0.190 / 0.172 | 0.075 / 0.064 | 0.101 / 0.083 |
| 5/16 in | 24 UNF / 18 UNC | 0.500 / 0.489 | 0.230 / 0.208 | 0.084 / 0.072 | 0.122 / 0.100 |
| 3/8 in | 24 UNF / 16 UNC | 0.562 / 0.551 | 0.295 / 0.270 | 0.094 / 0.081 | 0.156 / 0.131 |