# Shoulder screws ASME B18.3 (inch): shoulder Ø 1/4 to 3/4 in, thread, head size, hex key, thread length

> What are the dimensions of an ASME B18.3 inch socket shoulder screw: shoulder diameter, thread, head diameter and height, hex key, thread length?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: ASME B18.3-2003 shoulder screw tables as published by AFT Fasteners and Holo-Krome; McMaster-Carr linked for CAD
- Page: https://xemstudio.com/objects/shoulder-screws-asme-b18-3/ · JSON: https://xemstudio.com/api/geometry?object=shoulder-screws-asme-b18-3 · Plain text: https://xemstudio.com/objects/shoulder-screws-asme-b18-3/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- ASME B18.3 socket shoulder screws: the shoulder diameter is the size name (1/4 in shoulder = #10-24 thread, 5/16 = 1/4-20, 3/8 = 5/16-18, 1/2 = 3/8-16, 5/8 = 1/2-13, 3/4 = 5/8-11). The shoulder is ground slightly under nominal (for 1/4 in: .2480 / .2460 max / min; 5/16: .3105 / .3085; 3/8: .3730 / .3710; 1/2: .4980 / .4960; 5/8: .6230 / .6210; 3/4: .7480 / .7450 or .7460), so a bore for it is nominal plus your clearance.
- Two independent tables (AFT Fasteners' B18.3-2003 sheet and Holo-Krome's shoulder screw sheet) agree on shoulder D max / min, head diameter A, head height H, hex key J, key engagement T and thread length E for all six sizes. Only the .7450 vs .7460 minimum for the 3/4 in shoulder differs. Other columns (neck diameters, fillet radii, chamfer C) are printed in both but their column assignment was ambiguous in extraction, so they are not used.
- Shoulder length is the dimension you select; the two sheets above do not print a length range, so no standard lengths are claimed here. Shoulder length tolerance: −.02 in up to 3/8 in shoulder, −.03 in above (AFT). McMaster-Carr carries these in inch sizes (shoulder length in 1/8 in or 1/4 in steps by size); the category links are below.
- Files: six solids, one per size, with an example 1 in (25.4 mm) shoulder length. Thread is drawn as a plain cylinder at the nominal major diameter (from the thread designation; #10 = .190 in) over the thread length E; head diameter and height are the maxima; socket depth is the minimum key engagement T. No chamfers, fillets or thread neck. Left out: larger shoulders (1 in and up), which neither sheet's text carried legibly.
- Metric ISO 7379 shoulder screws are on the companion page.

## Sizes

| shoulder Ø D (nominal) | thread | head Ø A (max), in (mm) | head height H (max), in (mm) | hex key J, in (mm) | key engagement T (min), in | thread length E, in (mm) |
|---|---|---|---|---|---|---|
| 1/4 (6.35 mm) | #10-24 | 0.375 (9.52) | 0.188 (4.78) | 1/8 (3.17) | 0.094 | 0.375 (9.52) |
| 5/16 (7.94 mm) | 1/4-20 | 0.438 (11.13) | 0.219 (5.56) | 5/32 (3.97) | 0.117 | 0.438 (11.13) |
| 3/8 (9.52 mm) | 5/16-18 | 0.562 (14.27) | 0.250 (6.35) | 3/16 (4.76) | 0.141 | 0.500 (12.70) |
| 1/2 (12.70 mm) | 3/8-16 | 0.750 (19.05) | 0.312 (7.92) | 1/4 (6.35) | 0.188 | 0.625 (15.88) |
| 5/8 (15.88 mm) | 1/2-13 | 0.875 (22.22) | 0.375 (9.52) | 5/16 (7.94) | 0.234 | 0.750 (19.05) |
| 3/4 (19.05 mm) | 5/8-11 | 1.000 (25.40) | 0.500 (12.70) | 3/8 (9.52) | 0.281 | 0.875 (22.22) |

## Where the files are

- AFT Fasteners: [Socket shoulder screw dimensions (alloy steel), ASME B18.3-2003](https://aftfasteners.com/socket-shoulder-screws-dimensions-mechanical-properties) — web — Publisher's page; dimensions are facts
- Holo-Krome (Global Industrial PDF): [Socket shoulder screw dimensions (D, A, H, J, T, E)](https://www.globalindustrial.com/site/images/holokrome/socketshoulder.pdf) — web — Publisher's page; dimensions are facts
- McMaster-Carr: [Steel shoulder screws (inch and metric) (free STEP/IGES per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/steel-shoulder-screws/) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)
- McMaster-Carr: [Shoulder screws, ISO 7379 filter (free STEP/IGES per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/shoulder-screws/specifications-met~iso-7379) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)

## Free STEP/STL (6 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/index.json

- shoulder-screw-b18-3-1-4in-shoulder-no10-24: [STEP](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-1-4in-shoulder-no10-24.step) · [STL](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-1-4in-shoulder-no10-24.stl) — ASME B18.3 shoulder screw, 1/4 in shoulder (Ø6.35 mm) × 1 in (25.4 mm) long, thread #10-24 × 0.375 in (9.52 mm) drawn as a plain Ø4.83 mm cylinder, head Ø0.375 × 0.188 in (max), 1/8 in hex socket 0.094 in deep (key engagement min); the 1 in shoulder length is an example, not a published value; no chamfers, fillets or thread neck
- shoulder-screw-b18-3-5-16in-shoulder-1-4-20: [STEP](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-5-16in-shoulder-1-4-20.step) · [STL](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-5-16in-shoulder-1-4-20.stl) — ASME B18.3 shoulder screw, 5/16 in shoulder (Ø7.94 mm) × 1 in (25.4 mm) long, thread 1/4-20 × 0.438 in (11.13 mm) drawn as a plain Ø6.35 mm cylinder, head Ø0.438 × 0.219 in (max), 5/32 in hex socket 0.117 in deep (key engagement min); the 1 in shoulder length is an example, not a published value; no chamfers, fillets or thread neck
- shoulder-screw-b18-3-3-8in-shoulder-5-16-18: [STEP](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-3-8in-shoulder-5-16-18.step) · [STL](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-3-8in-shoulder-5-16-18.stl) — ASME B18.3 shoulder screw, 3/8 in shoulder (Ø9.52 mm) × 1 in (25.4 mm) long, thread 5/16-18 × 0.500 in (12.70 mm) drawn as a plain Ø7.94 mm cylinder, head Ø0.562 × 0.250 in (max), 3/16 in hex socket 0.141 in deep (key engagement min); the 1 in shoulder length is an example, not a published value; no chamfers, fillets or thread neck
- shoulder-screw-b18-3-1-2in-shoulder-3-8-16: [STEP](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-1-2in-shoulder-3-8-16.step) · [STL](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-1-2in-shoulder-3-8-16.stl) — ASME B18.3 shoulder screw, 1/2 in shoulder (Ø12.70 mm) × 1 in (25.4 mm) long, thread 3/8-16 × 0.625 in (15.88 mm) drawn as a plain Ø9.52 mm cylinder, head Ø0.750 × 0.312 in (max), 1/4 in hex socket 0.188 in deep (key engagement min); the 1 in shoulder length is an example, not a published value; no chamfers, fillets or thread neck
- shoulder-screw-b18-3-5-8in-shoulder-1-2-13: [STEP](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-5-8in-shoulder-1-2-13.step) · [STL](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-5-8in-shoulder-1-2-13.stl) — ASME B18.3 shoulder screw, 5/8 in shoulder (Ø15.88 mm) × 1 in (25.4 mm) long, thread 1/2-13 × 0.750 in (19.05 mm) drawn as a plain Ø12.70 mm cylinder, head Ø0.875 × 0.375 in (max), 5/16 in hex socket 0.234 in deep (key engagement min); the 1 in shoulder length is an example, not a published value; no chamfers, fillets or thread neck
- shoulder-screw-b18-3-3-4in-shoulder-5-8-11: [STEP](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-3-4in-shoulder-5-8-11.step) · [STL](https://xemstudio.com/files/hardware/shoulder-screws-asme-b18-3/shoulder-screw-b18-3-3-4in-shoulder-5-8-11.stl) — ASME B18.3 shoulder screw, 3/4 in shoulder (Ø19.05 mm) × 1 in (25.4 mm) long, thread 5/8-11 × 0.875 in (22.22 mm) drawn as a plain Ø15.88 mm cylinder, head Ø1.000 × 0.500 in (max), 3/8 in hex socket 0.281 in deep (key engagement min); the 1 in shoulder length is an example, not a published value; no chamfers, fillets or thread neck

## Questions

**What thread does a 1/2 in shoulder bolt have?**

3/8-16 with a 0.625 in long thread, 3/4 in head Ø × 5/16 in tall (0.312), 1/4 in hex key.

**What hex key fits a 5/16 in shoulder screw?**

5/32 in: the 5/16 in shoulder (1/4-20) screw has a .438 in head, .219 in tall, and a 5/32 in socket.

**What is the shoulder diameter tolerance?**

Ground under nominal: 1/2 in shoulder is .4980 max / .4960 min.

## Fits with

- [Shoulder screws ISO 7379 (metric): shoulder Ø, thread, head size, hex key, thread length, M5 to M20](https://xemstudio.com/objects/shoulder-screws-iso-7379/)
- [Socket head cap screws, inch: #10-24, #10-32, 5/16-18, 3/8-16, 1/2-13 (ASME B18.3)](https://xemstudio.com/objects/socket-head-cap-screws-inch/)
- [Button head socket cap screws, inch: #4-40 to 1/2-13 (ASME B18.3)](https://xemstudio.com/objects/button-head-socket-screws-inch/)
- [Clevis pins ISO 2341 B, Ø3 to Ø8](https://xemstudio.com/objects/clevis-pins/)
- [Hex bolts, inch: 1/4-20 to 3/4-10 (ASME B18.2.1)](https://xemstudio.com/objects/hex-bolts-inch/)
- [Imperial machine screws: #4-40, #6-32, #8-32, 1/4-20](https://xemstudio.com/objects/imperial-machine-screws/)