# Socket head cap screw, inch (ASME B18.3)

Hexagon socket head cap screw, 1960 series, Unified inch threads (UNC and UNF) #0-80 to 1/2-20, at any length. Presets
cover the common catalogue sizes (#4-40 × 1/2, 1/4-20 × 1, ...).

## Geometry

Envelope for assemblies:

- cylindrical head, diameter **A max**, height **H max**;
- hexagon socket, nominal key size **J**, depth **T** (key engagement, min), flat bottom;
- plain shank at the basic major diameter **D**, length **L** (`length`); the thread is not modelled.

The head's bearing face is on the XY plane at the origin, the head above it, the shank along -Z.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Thread, #0-80 to 1/2-20 (UNC and UNF) |
| `length` | Nominal length L under the head, inches |
| `material` | `steel` (alloy steel, black oxide), `stainless-18-8` (304), `stainless-316` |

## Sources

- **D**, basic major diameter (ASME B1.1): NBS Handbook H28 (1969) Part I, Table 2.7 "Unified standard screw thread
  series", column "Nominal size and basic major diameter" (printed p. 2.08,
  <https://nvlpubs.nist.gov/nistpubs/Legacy/hb/nbshandbook28-1969p1.pdf>); the same basic diameters head the B18.3
  tables below.
- **A max, H max, J, T min**: ASME B18.3-2012, Table 1 (hexagon socket head cap screws, 1960 series), as reproduced
  at <https://www.globalfastener.com/standards/detail_20304.html>; the same values in ASME B18.3-2003 Table 1A
  (<https://www.fasten.it/en/norms/norm/asme_b18.3_table_1a>, and <https://aftfasteners.com/socket-cap-screws-dimensions-and-mechanical-properties>),
  in Holo-Krome's *Technical Manual* (2015) Table 1, p. 1 (<https://holo-krome.com/uploads/7/2/7/5/72754089/hk_consolidated_tech_manual_full_2015.pdf>) and in Unbrako's *Engineering Guide*, p. 6
  (<https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/08/UnBrako-fasteners.pdf>; it prints 7/16 H max as .437, every other source .438).

A max, H max, J and T are the same in the 2003 and 2012 editions (they differ only in A min), so the values match
both; the recipe cites ASME B18.3-2012. Inch values as in the standard; the model converts them to millimetres (1 in = 25.4 mm).

| Size | D | A | H | J | T |
|---|---|---|---|---|---|
| #0 | 0.06 | 0.096 | 0.06 | 0.05 | 0.025 |
| #1 | 0.073 | 0.118 | 0.073 | 0.0625 | 0.031 |
| #2 | 0.086 | 0.14 | 0.086 | 0.078125 | 0.038 |
| #3 | 0.099 | 0.161 | 0.099 | 0.078125 | 0.044 |
| #4 | 0.112 | 0.183 | 0.112 | 0.09375 | 0.051 |
| #5 | 0.125 | 0.205 | 0.125 | 0.09375 | 0.057 |
| #6 | 0.138 | 0.226 | 0.138 | 0.109375 | 0.064 |
| #8 | 0.164 | 0.27 | 0.164 | 0.140625 | 0.077 |
| #10 | 0.19 | 0.312 | 0.19 | 0.15625 | 0.09 |
| 1/4 | 0.25 | 0.375 | 0.25 | 0.1875 | 0.12 |
| 5/16 | 0.3125 | 0.469 | 0.312 | 0.25 | 0.151 |
| 3/8 | 0.375 | 0.562 | 0.375 | 0.3125 | 0.182 |
| 7/16 | 0.4375 | 0.656 | 0.438 | 0.375 | 0.213 |
| 1/2 | 0.5 | 0.75 | 0.5 | 0.375 | 0.245 |

Preset list: sizes and lengths of the step.parts catalogue (MIT), see `library/NOTICE.md`.