FF-W-92 Flat Washers — Plain Solid & Laminated
The specification for FF-W-92 flat washers covers plain flat washers — highly specified solid or laminated washers with a centrally located hole and two flat, parallel bearing surfaces. They are utilized across military and industrial sectors to effectively distribute fastener loads, prevent surface damage, and provide structural clearance under a nut or bolt head. The current FF-W-92 revision B was published on May 9, 1974.
At a Glance
FF-W-92 Flat Washers Overview
FF-W-92 flat washers are fundamental Federal Specification fasteners designed to ensure the integrity of a bolted joint. These plain flat washers feature a centrally located hole, either a solid or laminated cross-section, and two flat, parallel bearing surfaces. Their core function in any assembly is to distribute a bolt or nut's clamping load over a significantly wider area than the fastener head alone.
The standard establishes highly specific dimensional rules to guarantee structural consistency. For example, the inner 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). Maximum thickness is capped at 25 percent of the largest outside dimension, while minimum thickness requirements scale based on the outside diameter (OD).
- Washers with fully separable lamination layers are typically classified as "shims" rather than falling under this specific washer standard.
- Washers fabricated from ceramic or specific electrically-rated materials fall under separate insulator classifications rather than FF-W-92.
- The specification excludes disk-type valve washers as well as graphite-impregnated or pre-lubricated washer products.
Load Distribution and Clearances
When installing FF-W-92 flat washers in industrial or military applications, their primary role is to ensure optimal load distribution to prevent embedding or galling of the base material. The precision surface finish mandated by FF-W-92 revision B ensures that rotational friction is minimized during tightening, allowing for accurate torque readings. Engineers and procurement specialists frequently rely on the Defense Logistics Agency (DLA) ASSIST portal to verify the latest material grades—such as Carbon Steel and Corrosion-Resistant Steel (CRES)—for these components.
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.
Frequently Asked Questions
What's excluded from FF-W-92?
Washers with separable lamination (classified as shims 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 these washers?
.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 compliant FF-W-92 solid or laminated washers with full material traceability and Mill Test Certification.
Prefer email? sales@anankafasteners.com
