# Socket set screw, inch (ASME B18.3)

Hexagon socket set screw (grub screw), Unified inch threads (UNC and UNF) #0-80 to 1/2-20. Presets
cover the catalogue sizes (cup point screws in the catalogue).

## Geometry

Envelope for assemblies: a plain cylinder at the basic major diameter **D**, overall length L (`length`), with a
hexagon socket of nominal key size **J** in its top end, flat-bottomed at the standard's minimum key engagement for
cup and flat point screws: **T_H min** for lengths L0 and longer, the short-length table's value below L0 (see
Sources). The thread and the point shape (cup, flat, cone, dog) are not modelled.

The top face is on the XY plane at the origin and the screw points along -Z.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Thread, #0-80 to 1/2-20 (UNC and UNF) |
| `length` | Overall length L, inches: L0 or longer, or one of the short-length table's lengths |
| `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 ASME
  B18.3 tables below.
- **J**, **T_H min** and **L0** (cup point): ASME B18.3-2012, Table 14 (hexagon socket set screws, cup point), as
  reproduced at <https://www.globalfastener.com/standards/detail_20314.html>; the same J and T_H in ASME B18.3-2003
  Table 5A (<https://www.fasten.it/en/norms/norm/asme_b18.3_table_5a>) and in Holo-Krome's *Technical Manual* (2015),
  Table 13, p. 16-17 (<https://holo-krome.com/uploads/7/2/7/5/72754089/hk_consolidated_tech_manual_full_2015.pdf>),
  whose note 3 says T_H applies only to nominal lengths equal to or longer than L0 (flat points have the same L0).
- **Short lengths**: Holo-Krome *Technical Manual* (2015), Table 14 "Hexagon key engagements for short length set
  screws", p. 18, column "cup and flat points" (single source; the table prints lengths as two-place decimals, Table
  13 note 1: 0.13 = 1/8 and so on). Lengths below L0 that this table does not list have no sourced key engagement and
  are refused.

The values are the same in ASME B18.3-2003 and B18.3-2012 for every column used here. Inch values as in the tables;
the model converts them to millimetres (1 in = 25.4 mm).

| Size | D | J | T_H min | L0 | Short lengths L: T min |
|---|---|---|---|---|---|
| #0 | 0.06 | 0.028 | 0.050 | 1/8 | 1/16: 0.030, 3/32: 0.040 |
| #1 | 0.073 | 0.035 | 0.060 | 1/8 | 1/16: 0.030, 3/32: 0.040 |
| #2 | 0.086 | 0.035 | 0.060 | 1/8 | 1/16: 0.030, 3/32: 0.040 |
| #3 | 0.099 | 0.05 | 0.070 | 3/16 | 3/32: 0.040, 1/8: 0.055 |
| #4 | 0.112 | 0.05 | 0.070 | 3/16 | 3/32: 0.045, 1/8: 0.060 |
| #5 | 0.125 | 0.0625 | 0.080 | 3/16 | 3/32: 0.040, 1/8: 0.060 |
| #6 | 0.138 | 0.0625 | 0.080 | 3/16 | 3/32: 0.040, 1/8: 0.060, 5/32: 0.070 |
| #8 | 0.164 | 0.078125 | 0.090 | 3/16 | 1/8: 0.060, 5/32: 0.070 |
| #10 | 0.19 | 0.09375 | 0.100 | 3/16 | 1/8: 0.060 |
| 1/4 | 0.25 | 0.125 | 0.125 | 1/4 | 3/16: 0.090 |
| 5/16 | 0.3125 | 0.15625 | 0.156 | 5/16 | 1/4: 0.125 |
| 3/8 | 0.375 | 0.1875 | 0.188 | 3/8 | 1/4: 0.110, 5/16: 0.140 |
| 7/16 | 0.4375 | 0.21875 | 0.219 | 7/16 | 3/8: 0.160 |
| 1/2 | 0.5 | 0.25 | 0.250 | 1/2 | 3/8: 0.175, 7/16: 0.215 |

Corrected in this audit: the socket was drawn min(L / 2, J) deep, a depth no source gives; it is now the standard's
minimum key engagement. The catalogue's 1/2 × 1/4 in screws (shorter than L0 = 1/2 in and not in the short-length
table) have no preset.

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