External Tooth Lock Washers
What are external tooth lock washers? External tooth lock washers, also called external star or serrated lock washers, have teeth that face outward around the outer edge. As the fastener is tightened, the twisted teeth flatten and bite into the surface and the bolt head, and because they act on a larger diameter they give strong resistance to loosening from vibration.
External vs internal tooth lock washers
The difference is where the teeth sit. External tooth washers put the teeth on the outer edge, acting on a larger diameter, which gives more rotational grip and stronger loosening resistance than internal tooth washers of the same size. They suit larger-head fasteners such as pan head and button head screws, where the head covers the outer teeth. Internal tooth washers hide the teeth under the bolt head for a cleaner look and tight spaces but with slightly less grip. Choose external tooth for maximum bite with larger heads, and select the material for the environment, from hardenable 410 to marine-grade 316.
Material choices for external tooth lock washers
- 410 stainless: hardened, springy stainless that holds tooth bite.
- 316 stainless: marine-grade corrosion resistance for coastal use.
- Metric 18-8 (A2): metric sizing, comparable to 304.
Common applications for external tooth lock washers
- Larger-head fasteners (pan, button head)
- High-grip vibration resistance
- Electrical bonding and grounding
- Machinery, equipment, and sheet metal
For teeth on the inner edge and a cleaner look, see internal tooth lock washers, and browse every option on the main lock washers category.
External Tooth Lock Washers FAQ
What is the difference between external and internal tooth washers?
External tooth washers have outward-facing teeth on a larger diameter for more grip. Internal tooth washers hide inward-facing teeth under the bolt head for a cleaner look and tight spaces.
What fasteners suit external tooth washers?
They work best with larger-head fasteners such as pan head and button head screws, where the head covers the outer teeth.
Do external tooth washers grip more than internal?
Yes. Because the teeth act on a larger diameter, external tooth washers usually give stronger rotational resistance than internal tooth washers of the same size.