Tooth Lock Washer
Washers · star washer · internal tooth washer · external tooth washer
Definition: A tooth lock washer has radial teeth that bite into the fastener and the mating surface, resisting loosening and ensuring electrical continuity.
Anatomy
■ Body■ Hole
Governing standards: ASME B18.21.1
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| #8 | M4 | 3/8 OD | 0.02 thick |
| 1/4 | M6 | 1/2 OD | 0.03 thick |
| 3/8 | M10 | 11/16 OD | 0.04 thick |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Spring steel | spring steel, zinc-plated | — | None |
| Stainless | spring stainless | — | None |
Materials
- Spring steel (zinc-plated)
- Stainless spring steel
- Phosphor bronze
Pros & Cons
Pros
- Teeth bite through paint and oxidation for good ground
- Prevents rotation under light vibration
- Cheap and compact
Cons
- Scar the mating surface
- Little effect once fully tightened
- Single-use in practice
Typical Uses
- Electrical grounding
- Appliance assembly
- Light anti-loosening
- Soft metal biting
Alternatives & Related
- Split Lock Washer — The other common anti-loosening washer
- Keps Nut — Nut with the tooth washer built in
Where to Buy
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FAQ
Internal vs external tooth washer?
Internal teeth sit under a small head and look neater; external teeth spread grip over a larger radius for more bite. Combination washers have both.
Do tooth lock washers work?
They help with electrical bonding and light vibration, but like split washers they are not a substitute for proper preload or a lock nut in critical joints.