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Stainless Steel Split Lock Washers 18-8 (304), Medium
Helical Spring Type • 1/4" to 3/4" • Bulk Quantities
Description
Fastenio helical spring (split) lock washers in 18-8 (304) stainless steel, Medium duty series. The split-coil design wedges its sharp cut edges into the nut face and the work surface, resisting back-off from vibration and load reversal.
Available in seven hole sizes from 1/4" through 3/4", in pack quantities from 5 (sample) up to 5,000 (production bulk). Manufactured to ASME B18.21.1 Medium series dimensions.
When to Use a Split Lock Washer
- Vibration-prone joints — machinery, motors, anything with rotating or reciprocating parts where standard nut friction alone may loosen.
- Stacked with a flat washer — the flat washer spreads the clamp load on the work surface; the split lock goes between flat washer and nut to bite both surfaces.
- Lower cost than a Nylon Insert Lock Nut — effective for most vibration scenarios at a fraction of the cost.
- Stainless on stainless — use 18-8 washers with 18-8 nuts and bolts to avoid galvanic mismatch in wet environments.
Material
Grade: 18-8 Stainless Steel (Type 304 / A2-70 equivalent) — austenitic alloy with excellent corrosion resistance in atmospheric, freshwater, and most chemical environments.
Finish: Plain (no plating). 18-8's self-renewing passive oxide layer provides natural corrosion protection.
Specification: ASME B18.21.1 Helical Spring Lock Washer, Medium series.
How to Order
Select your variation by Hole Size and Unit Quantity:
- Hole Size matches the bolt or screw diameter the washer is intended for (e.g., 1/4" lock washer for a 1/4" bolt).
- Medium Series — this is the standard duty class for general industrial use. Regular and Heavy series exist for lighter and heavier-duty applications respectively; Medium is by far the most common.
- Unit Quantity — 5 and 10 are sample/repair packs. 25–100 cover small projects. 250–5,000 are production-volume bulk.
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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 & Dimensions
All measurements in inches. Nominal Size matches the bolt diameter the washer is designed for. ID is the actual hole; OD is the outer diameter; Thickness is the spring-coil cross-section.
Nominal SizeInner Diameter (ID)Outer Diameter (OD)Thickness 1/4"0.260"0.487"0.062" 5/16"0.320"0.583"0.078" 3/8"0.380"0.682"0.094" 7/16"0.443"0.776"0.109" 1/2"0.505"0.870"0.125" 5/8"0.631"1.094"0.156" 3/4"0.756"1.312"0.172"
Applications
- Marine — deck hardware, fittings, anywhere salt-water resistance plus vibration tolerance is needed.
- HVAC — ductwork, compressor mounts, equipment frames, condensation-exposed joints.
- Industrial — machinery assembly, motor mounts, conveyor systems, equipment subject to vibration.
- Automotive — chassis, body brackets, exhaust hangers, mounting hardware.
- Construction — structural connections, brackets, signage, anchoring.
- Signs & Outdoor — signage, lighting fixtures, fencing, weather-exposed assemblies.
Notes
- Stack order: typical assembly is bolt → work surface → flat washer (optional) → split lock washer → nut. The lock washer must sit against the nut face for its sharp edges to bite.
- Galvanic compatibility: 18-8 washers pair best with 18-8 stainless bolts and nuts. Pairing stainless lock washers with carbon-steel bolts in wet environments will accelerate corrosion of the carbon-steel bolt.
- One-time use: split lock washers are not designed for repeated assembly/disassembly — the spring fatigues. Replace when reassembling critical joints.
- Vibration alternatives: for high-vibration applications, consider Nylon Insert Hex Lock Nuts (cross-linked below) which provide more robust locking.
Related Fastenio Products
SS Flat Washers 18-8
Stack below the lock washer for load distribution.
View →
SS Finished Hex Nuts 18-8
The nut goes against this lock washer for the clamp.
View →
SS Nylon Insert Lock Nuts
Alternative locking method for high vibration.
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