ASME B18.21.1 Internal Tooth Lock Washers — Inch Series (No. 2 – 1 1/4 in)
ASME B18.21.1 internal tooth lock washer dimensions for inch-series screws — inside diameter, outside diameter and thickness per nominal size from No. 2 through 1 1/4 in, with the inward-facing tooth count the source prints, transcribed row-for-row.
Last updated: 2026-11
Specifications
The internal tooth lock washer puts its teeth where the fastener is: an inward-facing ring of hardened points that bites both the screw's bearing face and the washer's own underside when the fastener is torqued, with the teeth riding inside the bearing circle — so it works under low-profile and clearance-restricted heads (pan, fillister, some socket heads) where an external-tooth ring would stand prouder than the head itself or overhang the mating recess. The collected chart covers No. 2 through 1 1/4 in with ID, OD, thickness and the tooth count the source prints per size. Ordering nuances that the chart pins down: teeth count is a per-size fixed value (roughly six on small sizes rising on larger), and the OD of an internal-tooth washer stays close to the head's bearing diameter — which is exactly why it is the countersunk-and-pan-head companion. Like all functional lock washers it must be through-hardened; material and hardness are not tabulated — per RFQ. For vibration-heavy duty, pair the choice with the joint's dynamics; the tooth rings excel at light-preload, small-screw electrical and electronic hardware, and underperform where preload is high or joints see thermal cycling — engineered locking is an RFQ conversation.
| Standard | ASME B18.21.1 — internal tooth lock washers, inch series |
|---|---|
| Size range | Nominal screw sizes No. 2 – 1 1/4 in, 22 printed rows |
| Tabulated limits (in) | Per row: inside diameter max/min, outside diameter max/min, thickness max/min, plus teeth count as printed per size |
| Function | Inward-facing hardened teeth bite the fastener bearing face and washer underside under torque; rides inside the head bearing circle — suits pan/fillister and countersunk heads where external teeth would stand proud |
| Hardness / finish / material | Not tabulated by the collected chart — per RFQ; functional locking requires through-hardened material — state hardness and finish |
| Nominal Size (thread dia.) | A — Inside Dia. (max) | A (min) | B — Outside Dia. (max) | B (min) | C — Thickness (max) | C (min) |
|---|---|---|---|---|---|---|
| No.2 (0.086) | 0.095 | 0.089 | 0.200 | 0.175 | 0.016 | 0.010 |
| No.3 (0.099) | 0.109 | 0.102 | 0.232 | 0.215 | 0.016 | 0.010 |
| No.4 (0.112) | 0.123 | 0.115 | 0.270 | 0.245 | 0.018 | 0.012 |
| No.5 (0.125) | 0.136 | 0.129 | 0.280 | 0.255 | 0.020 | 0.014 |
| No.6 (0.138) | 0.150 | 0.141 | 0.295 | 0.275 | 0.022 | 0.016 |
| No.8 (0.164) | 0.176 | 0.168 | 0.340 | 0.325 | 0.023 | 0.018 |
| No.10 (0.190) | 0.204 | 0.195 | 0.381 | 0.365 | 0.024 | 0.018 |
| No.12 (0.216) | 0.231 | 0.221 | 0.410 | 0.394 | 0.027 | 0.020 |
| 1/4 (0.250) | 0.267 | 0.256 | 0.478 | 0.460 | 0.028 | 0.023 |
| 5/16 (0.3125) | 0.332 | 0.320 | 0.610 | 0.594 | 0.034 | 0.028 |
| 3/8 (0.375) | 0.398 | 0.384 | 0.692 | 0.670 | 0.040 | 0.032 |
| 7/16 (0.4375) | 0.464 | 0.448 | 0.789 | 0.740 | 0.040 | 0.032 |
| 1/2 (0.500) | 0.530 | 0.512 | 0.900 | 0.867 | 0.045 | 0.037 |
| 9/16 (0.5625) | 0.596 | 0.576 | 0.985 | 0.957 | 0.045 | 0.037 |
| 5/8 (0.625) | 0.663 | 0.640 | 1.071 | 1.045 | 0.050 | 0.042 |
| 11/16 (0.6875) | 0.728 | 0.704 | 1.166 | 1.130 | 0.050 | 0.042 |
| 3/4 (0.750) | 0.795 | 0.769 | 1.245 | 1.220 | 0.055 | 0.047 |
| 13/16 (0.8125) | 0.861 | 0.832 | 1.315 | 1.290 | 0.055 | 0.047 |
| 7/8 (0.875) | 0.927 | 0.894 | 1.410 | 1.364 | 0.060 | 0.052 |
| 1 (1.000) | 1.060 | 1.019 | 1.637 | 1.590 | 0.067 | 0.059 |
| 1 1/8 (1.125) | 1.192 | 1.144 | 1.830 | 1.799 | 0.067 | 0.059 |
| 1 1/4 (1.250) | 1.325 | 1.275 | 1.975 | 1.921 | 0.067 | 0.059 |
Materials
- Through-hardened spring steel or stainless is the functional requirement; soft stampings flatten without locking — specify hardness at RFQ
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASME B18.21.1 Internal Tooth Lock Washers — Inch Series (No. 2 – 1 1/4 in)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Internal or external tooth lock washer — what decides it, and where do tooth rings beat a helical spring washer?
The head decides it. Internal teeth ride inside the screw's bearing circle, so they fit under low-profile and countersunk heads without standing above the head face or overhanging a recess — the natural companion for pan, fillister and flat-head machine screws in electrical and electronic hardware. External teeth reach outside the bearing circle onto the mating surface: they hold harder against rotation and cover screws with generous bearing faces, but they need that real estate and are wrong under a countersink. Against a helical spring washer, the tooth rings win on three fronts in light-preload work: they act at the bearing faces directly (the split ring's force is a single section acting axially), they resist rotation of both the screw and the washer itself (a split ring can spin in service and lose bite), and their thickness is uniform — better under finished surfaces. Where they lose: high-preload structural joints and thermal-cycling service, where any tooth ring's hardened points embed and relax. Practical ordering: pick by head geometry first, then by vibration duty; state material and hardness at RFQ, because a non-hardened tooth ring is decoration — and the collected chart, which carries geometry and tooth counts only, will not warn you.
What is the MOQ and lead time for washers on this standard?
The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common inch sizes are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support