FF-W-92 — Washer, Flat (Plain)
FF-W-92 covers plain flat washers — solid or laminated discs with a centrally located hole and two flat, parallel bearing surfaces, used to distribute fastener load, prevent surface damage, and provide clearance under a nut or bolt head. Revision B was published May 9, 1974.
At a Glance
Overview
FF-W-92 covers plain flat washers — washers with a centrally located hole, a solid or laminated cross-section, and two flat, parallel bearing surfaces. Their core function is to distribute a bolt or nut's clamping load over a wider area than the fastener head alone, protect the joined material's surface from damage, and in some cases provide clearance or take up small gaps in a stack-up.
The specification's own dimensional rules are notably specific: the hole diameter must be 75 percent or less of the washer's largest outside dimension, and the bearing surface finish must be better than 32 microinches (0.8 micrometers). Thickness is capped at 25 percent of the largest outside dimension, with a minimum thickness of .006" (0.15mm) for washers under 1/4" (6mm) outside dimension, and .016" (0.4mm) for washers 1/4" (6mm) or larger.
- Washers with separable lamination layers are classified as "shim" rather than under this washer specification.
- Washers fabricated from ceramic or electrically-rated materials fall under a separate insulator classification rather than FF-W-92.
- Excludes disk-type valve washers and graphite-impregnated or pre-lubricated washer products.
Key Dimensional Rules
| Rule | Requirement |
|---|---|
| Hole Diameter | ≤ 75% of largest outside dimension |
| Bearing Surface Finish | Better than 32 microinch (0.8 µm) |
| Maximum Thickness | ≤ 25% of largest outside dimension |
| Minimum Thickness (OD < 1/4") | .006" (0.15mm) |
| Minimum Thickness (OD ≥ 1/4") | .016" (0.4mm) |
FF-W-92 covers plain flat washers only. For lock/tooth washers, see FF-W-100; for helical spring lock washers, see FF-W-84.
FF-W-92 — Frequently Asked Questions
What's excluded from FF-W-92?
Washers with separable lamination (classified as shim instead), ceramic or electrically-rated washers (classified as insulators), disk-type valve washers, and graphite-impregnated or pre-lubricated washer products.
What's the minimum thickness for an FF-W-92 washer?
.006" (0.15mm) for washers under 1/4" outside dimension, and .016" (0.4mm) for washers 1/4" or larger — with an overall thickness cap of 25% of the largest outside dimension.
Need FF-W-92 Flat Washers to Print?
Ananka Fasteners manufactures FF-W-92 flat washers with full material traceability and Mill Test Certification.
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