Tooth Lock Washers

Tooth lock washers are mechanical locking washers designed with hardened teeth—bent slightly out of plane—along their inner edge, outer edge, or both. As the fastener is tightened, these teeth bite into the fastener face and the mating surface simultaneously, creating multiple points of resistance against rotation. Unlike split lock washers, which rely primarily on spring tension, tooth lock washers depend on this mechanical "biting" action, making them especially effective in applications with high vibration, shock loading, or where a reliable electrical bonding/grounding path is also required.

Tooth lock washers are widely used in electrical and electronics assembly, automotive manufacturing, HVAC equipment, appliance production, and general machinery, particularly where consistent locking performance and surface contact matter more than pure spring force.

Within this category, Lily Bearing offers a comprehensive range of tooth lock washer types to suit different tooth configurations, fastener standards, and application needs:

• External-Tooth Lock Washers – Teeth positioned around the outer edge, providing a strong grip on the material being fastened and effective resistance against loosening.
• Metric External-Tooth Lock Washers – Sized to metric fastener standards for globally manufactured equipment and assemblies.
• Mil. Spec. External-Tooth Lock Washers – Manufactured to military specifications for consistent quality and performance in defense and high-reliability applications.
• Tight-Grip External-Tooth Lock Washers – Featuring sharper, more aggressive external teeth for enhanced holding power in demanding applications.
• Countersunk External-Tooth Lock Washers – Designed with a countersunk profile to sit flush under countersunk screw heads while still providing external-tooth locking action.
• Countersunk Tight-Grip External-Tooth Lock Washers – Combines a countersunk fit for flush installation with aggressive tooth design for superior resistance to loosening under heavy vibration.
• Internal-Tooth Lock Washers – Teeth positioned on the inner edge, gripping the fastener shank directly to prevent loosening.
• Metric Internal-Tooth Lock Washers – Sized to metric standards, ideal for applications requiring inner-edge locking with metric fasteners.
• Mil. Spec. Internal-Tooth Lock Washers – Built to military specifications for high-vibration or dynamic environments requiring certified reliability.
• Internal-Tooth Lock Washers for Soft Material – Designed with teeth profiles that provide secure grip without damaging softer substrates such as aluminum, plastic, or coated surfaces.
• Internal-/External-Tooth Lock Washers – Combine both internal and external teeth for dual-point contact, gripping the fastener and the material surface simultaneously for enhanced overall stability.

Each subcategory is available in a range of sizes, thicknesses, and material finishes (including carbon steel, stainless steel, and zinc-plated options) to meet diverse fastening and industrial requirements.

Frequently Asked Questions

What Is the Difference Between External-Tooth and Internal-Tooth Lock Washers?

External-tooth lock washers have teeth around the outer edge that grip the surrounding material, making them well-suited for larger fastener heads and softer or thinner materials. Internal-tooth lock washers have teeth on the inner edge that grip the fastener shank directly, and they are often preferred where a compact outer diameter is needed or where electrical grounding contact with the fastener is important.

When Should I Use an Internal-/External-Tooth Lock Washer Instead of a Single-Type Washer?

Internal-/external-tooth lock washers are ideal when maximum locking security is required, since the dual tooth configuration grips both the fastener and the mating surface at the same time, offering greater resistance to loosening under heavy vibration or dynamic loads.

Why Would I Choose a Countersunk Tooth Lock Washer?

Countersunk tooth lock washers are designed to sit flush with countersunk screw heads, maintaining a smooth surface finish while still delivering reliable tooth-locking performance—commonly needed in applications where a flat, low-profile assembly surface is required.

What Makes Tight-Grip External-Tooth Lock Washers Different From Standard Ones?

Tight-Grip versions feature sharper, more aggressive teeth geometry than standard external-tooth washers, providing stronger bite and increased resistance to loosening in high-vibration or heavy-duty applications.

Are Tooth Lock Washers Suitable for Soft or Delicate Materials?

Standard tooth lock washers can mark or damage soft materials such as aluminum, plastic, or coated surfaces. For these applications, Internal-Tooth Lock Washers for Soft Material are specifically designed to provide secure locking without damaging the substrate.

Do Mil. Spec. Tooth Lock Washers Offer Any Advantage Over Standard Washers?

Yes. Mil. Spec. tooth lock washers are manufactured and tested to strict military specifications for material composition, dimensional accuracy, and performance consistency, making them suitable for aerospace, defense, and other applications with rigorous reliability requirements.

Can Tooth Lock Washers Be Used for Electrical Grounding Applications?

Yes. Because the teeth bite directly into both the fastener and the mating surface, tooth lock washers (particularly internal-tooth and internal-/external-tooth types) are commonly used to establish a reliable electrical bonding or grounding path in electrical and electronics assemblies.