# Square drive sizes ISO 1174: 1/4, 3/8, 1/2, 3/4, 1 in drive (6.3, 10, 12.5, 20, 25 mm): male and female square limits + stub rail and pocket plate

> What are the dimensions of a 1/4, 3/8, 1/2, 3/4 and 1 inch square drive (socket wrench square), male and female?

- Category: Hardware › Hand tool interfaces
- Kind: Standard part
- Basis: ISO 1174-1:1996 free sample (male squares types A and B, female squares types C and D, separation force); two Xem-drawn example plates for rack and holder design
- Page: https://xemstudio.com/objects/square-drive-iso-1174-1-4-to-1-in/ · JSON: https://xemstudio.com/api/geometry?object=square-drive-iso-1174-1-4-to-1-in · Plain text: https://xemstudio.com/objects/square-drive-iso-1174-1-4-to-1-in/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
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## Overall (mm)

| length | width | height |
|---|---|---|
| 121.0 | 41.4 | 18.0 |

**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## Notes

- The square drive on ratchets, extensions and sockets is ISO 1174-1: nominal sizes 6.3, 10, 12.5, 20 and 25 mm, which are the 1/4, 3/8, 1/2, 3/4 and 1 in drives. The male square s1 is 6.35 / 9.53 / 12.70 / 19.05 / 25.40 mm at its maximum (the inch fractions to the hundredth) with the minimum 0.09 to 0.13 mm lower. The female square s2 limits (the hole in the socket) are above the male: 6.63 / 6.41, 9.80 / 9.58, 13.03 / 12.76, 19.44 / 19.11, 25.79 / 25.46 mm (max / min). The minimum separation force of the retaining detent is 4, 11, 25 and 45 N for 6.3, 10, 12.5 and 20 mm (no 25 mm value was readable).
- The standard's free sample prints other columns (the corner dimensions e1 and e2, the retaining hole d2, depths l2 and l3, corner radii r1 and r2), but the OCR of this sample is partly garbled and those columns could not be assigned to sizes with confidence, so they are not listed. The detent ball size and the retaining-hole position are not specified in the sample (the text only says a female square with a retaining hole, not a recess, is used with a plunger retainer), so no detent ball diameter is given: measure the ball on the tool you design to. McMaster-Carr and other catalogues list drive sizes only.
- Tool-holder use: a rack that holds sockets by the square needs a male stub of s1 max or slightly under (a socket's female square is s2 min or larger, and must slide over the post); a handle or adapter with a female square needs a hole of at least s2 min. The two plates are Xem examples drawn at true size: the stub rail posts at s1 max, the pocket plate holes at s2 min. For sockets that must grip, use the standard's separation force and your own detent.
- Not here: socket bodies and wall thickness (ASME B107.1), impact-socket squares and their pin holes (ISO 2725 / ASME B107.4 are separate standards), ratchet head sizes, spline and wobble drives, and 1-1/2 in and larger squares.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| male square s1 | 6.35 / 9.53 / 12.70 / 19.05 / 25.40 mm max (1/4, 3/8, 1/2, 3/4, 1 in) | female square of a socket or adapter: s2 min 6.41 / 9.58 / 12.76 / 19.11 / 25.46 mm | slide | square-drive-stub* |
| female square s2 | 6.41 / 9.58 / 12.76 / 19.11 / 25.46 mm min | male square on a ratchet, extension or stub: the male is s1 max or less | slide | square-drive-female* |

## Sizes

| nominal (mm) | drive (in) | male s1 max (mm) | male s1 min (mm) | female s2 max (mm) | female s2 min (mm) | min separation force (N) |
|---|---|---|---|---|---|---|
| 6.3 | 1/4 | 6.35 | 6.26 | 6.63 | 6.41 | 4 |
| 10 | 3/8 | 9.53 | 9.44 | 9.80 | 9.58 | 11 |
| 12.5 | 1/2 | 12.70 | 12.59 | 13.03 | 12.76 | 25 |
| 20 | 3/4 | 19.05 | 18.92 | 19.44 | 19.11 | 45 |
| 25 | 1 | 25.40 | 25.27 | 25.79 | 25.46 | — |

## Where the files are

- ISO (iTeh Standards free sample): [ISO 1174-1:1996 square drive: male squares (types A, B) and female squares (types C, D), 6.3 to 25 mm, separation force](https://cdn.standards.iteh.ai/samples/23590/fd20f8b72777452ba01817d07f90c2e8/ISO-1174-1-1996.pdf) — web — Standards body sample pages; dimensions are facts

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/square-drive-iso-1174-1-4-to-1-in/index.json

- square-drive-stub-rail-1-4-to-1: [STEP](https://xemstudio.com/files/hardware/square-drive-iso-1174-1-4-to-1-in/square-drive-stub-rail-1-4-to-1.step) · [STL](https://xemstudio.com/files/hardware/square-drive-iso-1174-1-4-to-1-in/square-drive-stub-rail-1-4-to-1.stl) — stub rail, 121.0 × 41.4 × 18.0 mm: five square posts at the ISO 1174-1 male square s1 max 6.35, 9.53, 12.70, 19.05 and 25.40 mm (1/4, 3/8, 1/2, 3/4, 1 in), 14 mm tall on a 4 mm base; base, post height and spacing are Xem choices, the post sizes are the standard's; add your process allowance only where a socket's female square must clear the post (the standard's own clearance is the s2 min)
- square-drive-female-pocket-plate-1-4-to-1: [STEP](https://xemstudio.com/files/hardware/square-drive-iso-1174-1-4-to-1-in/square-drive-female-pocket-plate-1-4-to-1.step) · [STL](https://xemstudio.com/files/hardware/square-drive-iso-1174-1-4-to-1-in/square-drive-female-pocket-plate-1-4-to-1.stl) — female square pocket plate, 111.3 × 39.5 × 10 mm: five through square holes at the ISO 1174-1 female s2 min 6.41, 9.58, 12.76, 19.11 and 25.46 mm, smallest first; plate size and thickness are Xem choices

## Questions

**What size is a 3/8 inch square drive?**

The male square is 9.53 mm (0.375 in) at its maximum and 9.44 mm at its minimum; the female square is 9.58 to 9.80 mm (ISO 1174-1, size 10).

**What size is a 1/2 inch drive square?**

12.70 mm max / 12.59 mm min male; 12.76 to 13.03 mm female; separation force at least 25 N.

**Is the detent ball size standardised?**

Not in the free ISO 1174-1 sample used here: it does not specify the ball or the retaining hole, so measure the part you design to.

## Fits with

- [Hex bit shank 1/4 in (ISO 1173 C 6.3 and E 6.3): across flats 6.35 mm, across corners 7.18 mm, form C and E dimensions, 4–12.5 mm sizes + hex pocket gauge](https://xemstudio.com/objects/hex-bit-shank-iso-1173-1-4-in/)
- [Hex keys (Allen keys): ISO 2936 metric 0.7–36 mm and ASME B18.3 inch .050–7/8 in: across flats, across corners, long and short arm + 31 key models](https://xemstudio.com/objects/hex-keys-iso-2936-asme-b18-3/)
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/)