#4 Nylon Flat Washers: Sizing and When to Use Them
By Mutual Screw & Supply | Published: 2026-11-01
Category: Buying Guides
A practical buying guide to #4 nylon flat washers with 1/4-inch OD and .093-inch thickness, including sizing checks, insulation uses, and clear decision rules.
Quick answer
Choose #4 nylon flat washers with a 1/4-inch outside diameter and .093-inch thickness when you need a small, non-conductive washer that spreads load without scratching the surface. Verify the #4 screw size and the .115-inch inside diameter before ordering.
Why the .093-inch thickness changes the decision
A .093-inch nylon washer is thick enough to act as a distinct spacer and insulator, not just a thin shim. That extra thickness can matter when you are trying to keep a metal fastener head away from a conductive surface or when you need a little more clearance under the head. It also means the washer will compress slightly under load, so do not treat it as a rigid metal spacer. If your assembly depends on precise stack height, account for that compression or choose a metal washer instead.
Where nylon beats metal, and where it does not
Nylon is the right call when electrical insulation, surface protection, or mild vibration damping matters more than high clamp load. It will not rust and it will not scratch painted or soft surfaces. But nylon has lower strength and temperature resistance than steel, so it is a poor fit for high-torque joints, hot environments, or applications where the washer must carry a structural load. For those cases, a metal flat washer is the safer choice.
Sizing pitfalls with #4 washers
#4 is a small screw size, and the washer dimensions matter more than the label. The inside diameter must clear the screw thread, and the outside diameter must fit inside the bearing area without overhanging into a counterbore or edge. A 1/4-inch outside diameter is compact, so check that it still covers enough surface to spread the load. If the washer is too small, it can pull into soft material; if it is too large, it may interfere with nearby components.
Decision rules for #4 nylon flat washers
- Check the screw size first: Use these washers only with #4 screws. Confirm the screw is actually #4, not a metric M3 or a different imperial size, because the .115-inch inside diameter is sized for #4. If the screw is not #4, stop and match the washer to the actual screw diameter.
- Match the outside diameter to the bearing area: A .250-inch outside diameter is small. Measure the surface under the fastener head and make sure the washer sits fully on it without hanging over an edge or dropping into a hole. Overhang or drop-through means you need a different outside diameter.
- Use thickness as a design choice: The .093-inch thickness provides a defined spacer and insulation layer. If you need a thinner shim, this washer may be too thick; if you need a rigid spacer, nylon may be too soft. Thickness is not just a number; it changes clamp height and compression.
- Choose nylon for insulation and surface protection: Pick these washers when the goal is to isolate the fastener electrically or protect a soft, painted, or plated surface. Do not use them as a substitute for a hardened metal washer in structural or high-torque joints. Insulation and protection are the primary jobs; load-bearing strength is not.
Product facts
- #4 x 1/4" OD Flat Washers | .093" Thick | Nylon (400 / Pkg.): #4 flat washers made from nylon with a plain finish, .115-inch inside diameter, .250-inch outside diameter, and .093-inch thickness. These dimensions confirm the washer fits #4 screws and provides a compact, non-conductive bearing surface for small fasteners.
#4 x 1/4" OD Flat Washers | .093" Thick | Nylon (400 / Pkg.)
Who these washers fit
Best for
- Small #4 fastener assemblies that need electrical insulation
- Protecting painted, plastic, or soft metal surfaces from screw heads
- Light-duty spacing or vibration damping in electronics and light equipment
Not for
- High-torque or structural joints where a metal washer is required
- Applications with exposure to high heat or harsh chemicals
- Screws that are not #4 size
