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Commercial Flat Washers Stainless Steel 18-8 (304), Inch
Multi-Size • #2 to 2" • Measured Dimensions • Industrial-Grade Bulk Quantities
Description
Fastenio commercial flat washers in 18-8 (304) stainless steel for industrial, marine, automotive, HVAC, and general fastening use. Commercial pattern is the standard trade designation for stainless flat washers — a plain, unhardened washer specified by its actual dimensions rather than by a plated-steel pattern table.
Available in twenty nominal sizes from #2 to 2", in pack quantities from 1 (single piece) up to 5,000 (production-volume bulk). Every size is listed with its measured inside diameter, outside diameter and thickness in the table below.
Material
Grade: 18-8 Stainless Steel (Type 304 / A2-70 equivalent) — 18% chromium, 8% nickel austenitic alloy. Excellent corrosion resistance in atmospheric, freshwater, and most chemical environments.
Finish: Plain (no plating). The natural passive oxide layer of 18-8 provides self-renewing corrosion protection.
Pattern: Commercial flat washer, inch sizes. Published dimensions govern — see the table below.
When to Use a Flat Washer
- Load distribution — spreads the clamp load over a wider area than a nut or bolt head alone, preventing material indentation.
- Surface protection — protects finished or painted surfaces from being scarred by nut/bolt rotation during torque.
- Oversized or slotted holes — covers the gap when the bolt hole is larger than the bolt diameter.
- Stack with lock washers — flat washer goes against the work surface, then split lock washer, then nut. Pairs naturally with the Fastenio split-lock and finished hex nut listings (see related products below).
How to Order
Select your variation by Nominal Size and Unit Quantity:
- Nominal Size matches the bolt or screw diameter the washer is intended for (e.g., 1/4" washer for a 1/4" bolt). The inner hole is slightly larger than nominal so the bolt clears.
- Inner Diameter (ID) is the actual measured hole size, not the nominal bolt size. If clearance matters on your job, order to this number.
- Outer Diameter and Thickness are listed per size in the table below. Order to the table.
- Unit Quantity — 1 and 5 are sample/repair packs. 10–100 cover small projects. 250–5,000 are production-volume bulk.
Built for repeat buyers. Clean listings, accurate item specifics, fast US shipping, and responsive support before and after the sale.
Not sure which size you need? Message us with your bolt size and the ID, OD and thickness your job calls for, and we'll confirm the right part before you order.
Need it faster? UPS 2nd Day Air and Next Day Air are available by request — message us with your ZIP code before purchase for a quote.
Need a larger quantity? Volume pricing is available beyond the listed pack sizes — message us with your target qty and we'll quote.
Available Sizes & Measured Dimensions
All measurements in inches. Inner Diameter is the actual measured hole diameter, not the nominal bolt size. Outer Diameter and Thickness are confirmed against our supplier's specifications.
Nominal SizeInner Diameter (ID)Outer Diameter (OD)Thickness #20.086"1/4"0.032" #40.130"5/16"0.031" #50.144"7/16"0.047" #60.158"3/8"0.031" #80.174"3/8"0.032" #100.219"1/2"0.050" #120.234"1/2"0.050" 1/4"0.285"5/8"0.050" 5/16"0.345"3/4"0.050" 3/8"0.407"7/8"0.050" 7/16"0.499"1-1/8"0.050" 1/2"0.568"1-1/4"0.062" 9/16"0.625"1-3/8"0.078" 5/8"0.688"1-1/2"0.078" 7/8"0.938"2"0.100" 1"1.062"2"0.125" 1-1/8"1.193"2-1/2"0.125" 1-1/4"1.312"2-3/4"0.125" 1-1/2"1.568"3-1/4"0.140" 2"2.123"4"0.187"
Applications
- Marine — boat fittings, deck hardware, anywhere salt-water corrosion is a concern.
- HVAC — ductwork, condenser frames, equipment mounting, condensation-exposed joints.
- Industrial — machinery assembly, conveyor systems, equipment frames, repair work.
- Automotive — chassis, body brackets, trim, exhaust hangers.
- Construction — structural connections, brackets, signage, fencing.
- Signs & Outdoor — weather-exposed assemblies, lighting fixtures, mounting hardware.
Notes
- Galvanic compatibility: 18-8 washers pair best with stainless or non-conductive substrates. Pairing stainless washers with carbon-steel bolts in wet environments will accelerate corrosion of the carbon-steel bolt.
- Stack order: typical assembly is bolt → work surface → flat washer → split lock washer (optional) → nut. Reverse the order if you want the lock washer on the bolt-head side.
- Need extra-large OD? See our SS Fender Washers (cross-linked below) for a larger outer diameter on thin or soft material.
- Vibration-prone joints: use a split lock washer or a Nylon Insert Lock Nut for added vibration resistance.
Related Fastenio Products
SS Finished Hex Nuts 18-8
The natural pair to stack with these washers.
View →
SS Split Lock Washers 18-8
Add vibration resistance to the joint.
View →
SS Fender Washers 18-8
Larger OD for thin or soft material.
View → Visit the Fastenio Store for More Fasteners → FASTENIO – Industrial-grade fasteners engineered for strength, precision, and lasting performance.
