Hillman Fasteners 300021 Split Lock Washer 5/16 in 100 Pack

Product Description

The HILLMAN FASTENERS 300021 is a 5/16-inch split lock washer supplied in a 100-piece pack. Split lock washers are used under fastener heads or nuts to resist loosening caused by vibration and torque relaxation. The helical split design bites into both the fastener bearing surface and the mating material, creating resistance to rotation. Constructed from zinc plated steel, the 300021 offers basic corrosion resistance suited to indoor and light-duty outdoor fastening applications. These washers are a standard consumable stocked by electricians, HVAC technicians, plumbers, and general contractors.

Split lock washers in the 5/16-inch size are commonly used with 5/16-inch bolts and screws across a wide range of trade and mechanical applications. Typical installations include equipment mounting, panel attachment, pipe hanger assembly, and structural fastening where vibration or movement could loosen a connection over time. The 100-piece pack quantity makes this suitable for job-site use or shop stock replenishment.

Key Features

• 5/16-inch inside diameter fits standard 5/16-inch fasteners
• Helical split design resists loosening under vibration and dynamic loads
• Zinc plated steel construction provides basic corrosion resistance
• 100-piece pack quantity supports bulk job-site or shop stock use
• Compatible with standard hex bolts, cap screws, and machine screws

Compatibility

Designed for use with 5/16-inch threaded fasteners in general mechanical, electrical, HVAC, and plumbing applications where split lock washers are specified.

Installation Notes

Install lock washers between the fastener head or nut and the mating surface before final torque is applied. Do not reuse lock washers that have been fully compressed, as the split will no longer provide adequate bite. Follow applicable fastener torque guidelines for the bolt grade and material being joined. No special tooling is required beyond standard hand or power wrenches.