# Split lock washer (DIN 127 B)

Split lock washer (spring washer) with square ends, DIN 127 form B, M2 to M100, with catalogue sizes as presets.

## Geometry

One helical turn of a rectangular section from the inner diameter **d1** (min) to the outer diameter **d2** (max),
thickness **s**, and free height **h** (form B, max). The section stays in the plane through the axis as it climbs,
so the washer is exactly h high and d2 wide; the split is where the two ends meet, h − s apart axially. The washer lies
on the XY plane at the origin and climbs along +Z.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Thread size, M2 to M100 |
| `material` | `spring-steel`, `stainless-a2`, `stainless-a4` |

## Source

DIN 127:1987-10, *Spring lock washers with square ends or tang ends*, dimension table (form B), read from the
reproduction on fasten.it (<https://fasten.it/norms/norm/din_127>; the only source found; fasteners.eu has no DIN 127 page) (mm).

| Size | d1 min | d2 max | s | h max (B) |
|---|---|---|---|---|
| M2 | 2.1 | 4.4 | 0.5 | 1.2 |
| M2.2 | 2.3 | 4.8 | 0.6 | 1.4 |
| M2.5 | 2.6 | 5.1 | 0.6 | 1.4 |
| M3 | 3.1 | 6.2 | 0.8 | 1.9 |
| M3.5 | 3.6 | 6.7 | 0.8 | 1.9 |
| M4 | 4.1 | 7.6 | 0.9 | 2.1 |
| M5 | 5.1 | 9.2 | 1.2 | 2.8 |
| M6 | 6.1 | 11.8 | 1.6 | 3.8 |
| M7 | 7.1 | 12.8 | 1.6 | 3.8 |
| M8 | 8.1 | 14.8 | 2 | 4.7 |
| M10 | 10.2 | 18.1 | 2.2 | 5.2 |
| M12 | 12.2 | 21.1 | 2.5 | 5.9 |
| M14 | 14.2 | 24.1 | 3 | 7.1 |
| M16 | 16.2 | 27.4 | 3.5 | 8.3 |
| M18 | 18.2 | 29.4 | 3.5 | 8.3 |
| M20 | 20.2 | 33.6 | 4 | 9.4 |
| M22 | 22.5 | 35.9 | 4 | 9.4 |
| M24 | 24.5 | 40 | 5 | 11.8 |
| M27 | 27.5 | 43 | 5 | 11.8 |
| M30 | 30.5 | 48.2 | 6 | 14.2 |
| M36 | 36.5 | 58.2 | 6 | 14.2 |
| M39 | 39.5 | 61.2 | 6 | 14.2 |
| M42 | 42.5 | 68.2 | 7 | 16.5 |
| M45 | 45.5 | 71.2 | 7 | 16.5 |
| M48 | 49 | 75 | 7 | 16.5 |
| M52 | 53 | 83 | 8 | 18.9 |
| M56 | 57 | 87 | 8 | 18.9 |
| M60 | 61 | 91 | 8 | 18.9 |
| M64 | 65 | 95 | 8 | 18.9 |
| M68 | 69 | 99 | 8 | 18.9 |
| M72 | 73 | 103 | 8 | 18.9 |
| M80 | 81 | 111 | 8 | 18.9 |
| M90 | 91 | 121 | 8 | 18.9 |
| M100 | 101 | 131 | 8 | 18.9 |

Preset list: sizes of the step.parts catalogue (MIT), see `library/NOTICE.md`. The catalogue's generic split lock washers name no standard; their presets use DIN 127 B. DIN 127 has no M33 size.