FF-W-100 — Washer, Lock (Tooth)
FF-W-100 covers tooth lock washers — washers with sharp, twisted teeth stamped around the internal or external edge that bite into the mating surfaces to resist loosening — for use in assemblies with bolts, studs, and machine screws. Revision C dates to January 29, 1969, with no superseding document identified.
At a Glance
Overview
FF-W-100 covers tooth lock washers — flat washers with a series of sharp, slightly twisted teeth stamped around either the inside diameter, the outside diameter, or both, used in assemblies with bolts, studs, and machine screws. As the fastener is tightened, the twisted teeth flex and bite into both the fastener head/nut face and the joined material, resisting rotation and helping maintain clamp load under vibration.
Unlike helical spring lock washers (FF-W-84), which rely primarily on axial spring tension, tooth lock washers work through direct mechanical engagement with the mating surfaces — making internal-tooth and external-tooth washers a common choice for electrical grounding connections, where the teeth also help cut through surface oxide or paint to establish a reliable electrical bond, in addition to lighter-duty mechanical locking applications.
- Internal-tooth washers place the teeth around the inner bore, keeping the outer edge smooth for a finished appearance.
- External-tooth washers place the teeth around the outer edge for maximum bite, often used where appearance is not a concern.
- Internal-external tooth washers combine both for maximum locking/grounding engagement.
Tooth Configuration Reference
For helical spring lock washers instead of tooth-style, see FF-W-84. For plain (non-locking) flat washers, see FF-W-92.
FF-W-100 — Frequently Asked Questions
How does a tooth lock washer differ from a spring lock washer?
A tooth lock washer resists loosening through direct mechanical engagement — its twisted teeth bite into both mating surfaces. A spring (helical) lock washer instead relies primarily on axial spring tension from its coiled, split cross-section.
Why are tooth lock washers common in electrical work?
The sharp teeth cut through surface oxide, paint, or other non-conductive coatings on the mating parts, helping establish a reliable low-resistance electrical bond in addition to their mechanical locking function.
Need FF-W-100 Tooth Lock Washers?
Ananka Fasteners manufactures FF-W-100 tooth lock washers in internal, external, and internal-external configurations with full material traceability.
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