Serrated Lockwashers
Our DIN 6798 J serrated lock washers carry their fine, overlapping teeth around the inside bore rather than the outer edge, making them the preferred serrated washer where the fastener head is smaller than the washer’s outer diameter or the bearing surface is irregular. Like the external-tooth version, the internal serration bites through coatings for reliable electrical bonding while resisting loosening from vibration.
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Serrated Lockwashers — Metric Sizes
What Is an Internal-Tooth Serrated Lockwasher?
The internal-tooth serrated lock washer is the Form J variant of DIN 6798, with its dense ring of fine teeth set around the inner bore rather than the outer rim. This arrangement concentrates the bite directly under the fastener head, which makes Form J the recommended choice whenever the screw or bolt head is smaller than the washer’s outside diameter, or when the bearing surface is convex, recessed, or otherwise non-flat — conditions where an external-tooth washer (Form A) would not seat its teeth evenly. As with all DIN 6798 serrated washers, the primary purpose is twofold: a frictional mechanical lock that supplements correct torque, and a reliable electrical bonding path created as the teeth cut through paint, plating, or oxide layers on the joined surfaces.
Key Features and Benefits
- Concentrated Bite Under the Head: Internal teeth seat directly beneath smaller fastener heads for consistent contact.
- Tolerant of Irregular Surfaces: Performs well on convex, recessed, or uneven bearing surfaces where external teeth would not seat evenly.
- Electrical Bonding: Teeth penetrate coatings to maintain a low-resistance electrical path.
- Compact Fit: Suited to socket head, pan head, and other smaller-diameter screw heads.
- Companion to Form A: Stocked alongside external-tooth washers to cover the full range of fastener head sizes.
Materials and Finishes
- Spring Steel, Phosphated: Standard finish for mechanical and electrical assemblies.
- Stainless Steel A2: General corrosion resistance.
- Stainless Steel A4: Marine and chemical environments.
Standards Compliance
- DIN 6798 J — Serrated lock washers, internal teeth
- DIN 6798 A — External tooth counterpart
- DIN 6798 V — Conical, countersunk form
Size Range and Availability
Available in M2 through M33 in metric coarse thread, in phosphated spring steel and A2/A4 stainless steel.
Frequently Asked Questions (FAQs)
1. When should I use internal-tooth instead of external-tooth serrated washers?
Use internal-tooth (Form J) washers when the fastener head is smaller than the washer’s outer diameter, or when the bearing surface is uneven, convex, or recessed.
2. What is the benefit of internal teeth?
Internal teeth concentrate contact directly under smaller fastener heads, giving more consistent bite than an external-tooth washer would in the same application.
3. Does this washer provide electrical grounding?
Yes. The internal teeth cut through coatings to maintain a reliable electrical bonding path, the same as the external-tooth version.
4. Can internal and external tooth serrated washers be used on the same job?
Yes — many assemblies stock both Form J and Form A to match the different screw head sizes used across a project.
5. What materials are available?
Phosphated spring steel, plus A2 and A4 stainless steel.
6. What sizes do you stock?
M2 through M33 in metric coarse thread.
7. Are these washers reusable?
Reuse is fine for non-critical assemblies, but the teeth deform after installation, so a new washer is recommended for critical or frequently serviced joints.
8. Will this washer damage the screw head?
Yes, by design — the teeth are meant to bite into the screw head and the work surface, so avoid using it on finished or cosmetic fasteners.
9. What standard governs this washer?
Internal-tooth serrated lock washers are manufactured to DIN 6798, Form J.
10. How does this differ from an internal-tooth washer made to DIN 6797?
DIN 6798 uses a finer, more numerous tooth pattern aimed primarily at electrical bonding, while DIN 6797 uses fewer, larger teeth aimed mainly at mechanical locking.
