# Split lock washers, inch (ASME B18.21.1): regular and high-collar spring washer ID, OD, thickness, width, #2 to 2 in

> What is the outside diameter and thickness of a 1/4 or 3/8 split lock washer, and how does a high-collar differ from a regular one?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: AFT Fasteners' regular / high-alloy table (ASME B18.21.1-1999) checked against the same table on a Tanner Bolt / CDE PDF, plus the same PDF family's high-collar sheet (ASME B18.21.1-2009); numbers only
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**Exact dimensions.** True size, with no tolerance added.

## Notes

- Inches (OD also in mm). Regular (and 'high-alloy', which AFT and the CDE sheet say is dimensionally identical): nominal size, inside diameter min and max, outside diameter max, minimum mean section thickness (T + t) / 2, minimum section width W. AFT and the CDE PDF give identical numbers for every regular row (#2 to 2 in).
- Column reading: both PDFs print a leading decimal that equals the nominal size, then two inside-diameter values and the OD. AFT lists the pair as min then max; the CDE sheet lists it larger-first with its own labels garbled, so the smaller of the pair is shown as ID min and the larger as ID max. The last two columns of each row are thickness and width: for regular washers they are 0.062 and 0.109 for 1/4 in (thickness first).
- High collar (CDE sheet, ASME B18.21.1-2009, #4 to 1-1/2): the sheet's column headers are garbled in the extracted text. Its last two numbers are shown as width W and thickness (T + t) / 2 because the radial width of a washer cannot exceed (OD − ID min) / 2, and for 1/4 in that is 0.0555 in, which fits 0.047 but not 0.078. Check this table against the standard before relying on it. Heavy and extra-duty split washers (a distributor sheet prints them) are not tabulated here.
- Not drawn: a split lock washer is a helix whose free height is not a column in any table read, so there is no honest solid; a flat ring would misstate it. Companion pages: tooth lock washers (tooth-lock-washers-inch-asme-b18-21-1), DIN 127 (spring-lock-washers-din-127-b) and Nord-Lock wedge washers. McMaster-Carr sells lock washers with per-part STEP; linked, not copied.

## Sizes

| type | size | nominal (in) | ID min (in) | ID max (in) | OD max (in) | width W min (in) | mean thickness (T+t)/2 min (in) | OD max (mm) |
|---|---|---|---|---|---|---|---|---|
| regular | #2 | 0.086 | 0.088 | 0.094 | 0.172 | 0.035 | 0.020 | 4.37 |
| regular | #3 | 0.099 | 0.101 | 0.107 | 0.195 | 0.040 | 0.025 | 4.95 |
| regular | #4 | 0.112 | 0.114 | 0.120 | 0.209 | 0.040 | 0.025 | 5.31 |
| regular | #5 | 0.125 | 0.127 | 0.133 | 0.236 | 0.047 | 0.031 | 5.99 |
| regular | #6 | 0.138 | 0.141 | 0.148 | 0.250 | 0.047 | 0.031 | 6.35 |
| regular | #8 | 0.164 | 0.167 | 0.174 | 0.293 | 0.055 | 0.040 | 7.44 |
| regular | #10 | 0.19 | 0.193 | 0.200 | 0.334 | 0.062 | 0.047 | 8.48 |
| regular | #12 | 0.216 | 0.220 | 0.227 | 0.377 | 0.070 | 0.056 | 9.58 |
| regular | 1/4 | 0.25 | 0.252 | 0.260 | 0.487 | 0.109 | 0.062 | 12.37 |
| regular | 5/16 | 0.312 | 0.314 | 0.322 | 0.583 | 0.125 | 0.078 | 14.81 |
| regular | 3/8 | 0.375 | 0.377 | 0.385 | 0.680 | 0.141 | 0.094 | 17.27 |
| regular | 7/16 | 0.438 | 0.440 | 0.450 | 0.776 | 0.156 | 0.109 | 19.71 |
| regular | 1/2 | 0.5 | 0.502 | 0.512 | 0.869 | 0.171 | 0.125 | 22.07 |
| regular | 9/16 | 0.562 | 0.564 | 0.574 | 0.965 | 0.188 | 0.141 | 24.51 |
| regular | 5/8 | 0.625 | 0.628 | 0.641 | 1.073 | 0.203 | 0.156 | 27.25 |
| regular | 3/4 | 0.75 | 0.753 | 0.766 | 1.265 | 0.234 | 0.188 | 32.13 |
| regular | 7/8 | 0.875 | 0.878 | 0.894 | 1.459 | 0.266 | 0.219 | 37.06 |
| regular | 1 | 1. | 1.003 | 1.024 | 1.656 | 0.297 | 0.250 | 42.06 |
| regular | 1-1/8 | 1.125 | 1.129 | 1.153 | 1.847 | 0.328 | 0.281 | 46.91 |
| regular | 1-1/4 | 1.25 | 1.254 | 1.280 | 2.036 | 0.359 | 0.312 | 51.71 |
| regular | 1-3/8 | 1.375 | 1.379 | 1.408 | 2.219 | 0.391 | 0.344 | 56.36 |
| regular | 1-1/2 | 1.5 | 1.504 | 1.534 | 2.419 | 0.422 | 0.375 | 61.44 |
| regular | 1-3/4 | 1.75 | 1.758 | 1.789 | 2.679 | 0.424 | 0.389 | 68.05 |
| regular | 2 | 2. | 2.008 | 2.039 | 2.936 | 0.427 | 0.422 | 74.57 |
| high collar | #4 | 0.112 | 0.114 | 0.120 | 0.173 | 0.022 | 0.022 | 4.39 |
| high collar | #6 | 0.138 | 0.141 | 0.148 | 0.216 | 0.030 | 0.030 | 5.49 |
| high collar | #8 | 0.164 | 0.167 | 0.174 | 0.267 | 0.042 | 0.047 | 6.78 |
| high collar | #10 | 0.19 | 0.193 | 0.200 | 0.294 | 0.042 | 0.047 | 7.47 |
| high collar | 1/4 | 0.25 | 0.252 | 0.260 | 0.363 | 0.047 | 0.078 | 9.22 |
| high collar | 5/16 | 0.3125 | 0.314 | 0.322 | 0.457 | 0.062 | 0.093 | 11.61 |
| high collar | 3/8 | 0.375 | 0.377 | 0.385 | 0.550 | 0.076 | 0.125 | 13.97 |
| high collar | 7/16 | 0.4375 | 0.440 | 0.450 | 0.644 | 0.090 | 0.140 | 16.36 |
| high collar | 1/2 | 0.5 | 0.502 | 0.512 | 0.733 | 0.103 | 0.172 | 18.62 |
| high collar | 9/16 | 0.5625 | 0.564 | 0.574 | 0.819 | 0.116 | 0.187 | 20.80 |
| high collar | 5/8 | 0.625 | 0.628 | 0.641 | 0.917 | 0.125 | 0.203 | 23.29 |
| high collar | 3/4 | 0.75 | 0.753 | 0.766 | 1.105 | 0.154 | 0.218 | 28.07 |
| high collar | 7/8 | 0.875 | 0.878 | 0.894 | 1.291 | 0.182 | 0.234 | 32.79 |
| high collar | 1 | 1. | 1.003 | 1.024 | 1.478 | 0.208 | 0.250 | 37.54 |
| high collar | 1-1/8 | 1.125 | 1.129 | 1.153 | 1.663 | 0.236 | 0.313 | 42.24 |
| high collar | 1-1/4 | 1.25 | 1.254 | 1.280 | 1.790 | 0.236 | 0.313 | 45.47 |
| high collar | 1-1/2 | 1.5 | 1.504 | 1.534 | 2.159 | 0.292 | 0.375 | 54.84 |

## Where the files are

- AFT Fasteners: [Regular and high-alloy split helical spring lock washers (ASME B18.21.1-1999), #2 to 2 in](https://www.aftfasteners.com/regular-high-alloy-split-helical-spring-lockwashers/) — web — Publisher's page; dimensions are facts
- Tanner Bolt / CDE sheet (Shopify CDN): [Split lock washers, regular and high-alloy, ASME B18.21.1-1999: ID, OD, thickness, width](https://cdn2.shopify.com/s/files/1/0056/7856/3437/files/Washerssplitalloy.pdf) — web — Maker datasheet; numbers only
- Tanner Bolt / CDE sheet (Shopify CDN): [High-collar helical spring lock washers (ASME B18.21.1-2009), #4 to 1-1/2](https://cdn2.shopify.com/s/files/1/0056/7856/3437/files/Washershicollar.pdf) — web — Maker datasheet; numbers only
- McMaster-Carr: [Split lock washers (regular and high collar) (free STEP/IGES per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/lock-washers/) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)

## Questions

**What is the OD of a 3/8 split lock washer?**

0.680 in max (regular, ASME B18.21.1); ID 0.377 to 0.385 in, minimum section width 0.141 in, minimum mean thickness 0.094 in.

**How is a high-collar lock washer different?**

Smaller OD and thicker, narrower section: for 1/4 in the OD max is 0.363 in against 0.487 in regular (CDE sheet; column assignment deduced, see notes).

**What ID does a 1/4 lock washer have?**

0.252 to 0.260 in for regular and high collar (1/4 in screw, nominal 0.250).

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