Hex Head Machine Screws
Small-diameter hex heads for machine assembly.
Machine screw sizes with hex heads, slotted or plain, in steel, stainless and brass.
Specifications & technical data.
Hex head machine screws to ASME B18.6.3 — the small-diameter hex family from #1 through 1/2″, in regular and large head patterns, fully threaded as standard.
Download our hex head machine screw dimensioning table (PDF)
| Nominal Size / Basic Screw Diameter | A — Regular Head | A — Large Head | H | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Width Across Flats | Min. Across Corners | Width Across Flats | Min. Across Corners | Head Height | |||||
| Max. | Min. | Max. | Min. | Max. | Min. | ||||
| #1 | 0.0730 | 0.125 | 0.120 | 0.134 | … | … | … | 0.044 | 0.036 |
| #2 | 0.0860 | 0.125 | 0.120 | 0.134 | … | … | … | 0.050 | 0.040 |
| #3 | 0.0990 | 0.188 | 0.181 | 0.202 | … | … | … | 0.055 | 0.044 |
| #4 | 0.1120 | 0.188 | 0.181 | 0.202 | 0.219 | 0.213 | 0.238 | 0.060 | 0.049 |
| #5 | 0.1250 | 0.188 | 0.181 | 0.202 | 0.250 | 0.244 | 0.272 | 0.070 | 0.058 |
| #6 | 0.1380 | 0.250 | 0.244 | 0.272 | … | … | … | 0.093 | 0.080 |
| #8 | 0.1640 | 0.250 | 0.244 | 0.272 | 0.312 | 0.305 | 0.340 | 0.110 | 0.096 |
| #10 | 0.1900 | 0.312 | 0.305 | 0.340 | … | … | … | 0.120 | 0.105 |
| #12 | 0.2160 | 0.312 | 0.305 | 0.340 | 0.375 | 0.367 | 0.409 | 0.155 | 0.139 |
| 1/4" | 0.2500 | 0.375 | 0.367 | 0.409 | 0.438 | 0.428 | 0.477 | 0.190 | 0.172 |
| 5/16" | 0.3125 | 0.500 | 0.489 | 0.545 | … | … | … | 0.230 | 0.208 |
| 3/8" | 0.3750 | 0.562 | 0.551 | 0.614 | … | … | … | 0.295 | 0.270 |
| 1/2" | 0.5000 | 0.750 | 0.735 | 0.820 | … | … | … | 0.400 | 0.367 |
All dimensions in inches, per ASME B18.6.3-2024. Typically stocked in 1/16″ length increments up to 5/8″, 1/8″ to 1-1/2″, and 1/4″ above. Confirm requirements with our estimating team.
Standards.
What are hex head machine screws?
Machine screws are the small end of the hex family — numbered sizes from #1 up through 1/2″, fully threaded, with an indented or trimmed hex head. They fasten panels, controls, terminals and equipment into tapped holes or with small nuts.
- Numbered sizes #1–#24 plus fractional to 1/2″
- Fully threaded as standard
- Regular and large head patterns
- Slotted or plain hex heads
Other names
- Hex machine screws
- Indented hex head screws
- Trim head hex screws
Tips for purchasing
- Pick regular or large head from the table — the large head buys bearing area on soft or slotted materials.
- Threads are UNC or UNF, class 2A as standard — name the series.
- Stainless 18-8 and 316 cover most corrosion service at this scale.
- Certs and traceability available on request.
Materials.
Representative capabilities — every item is manufactured or certified to your specification. Confirm requirements with our estimating team.
