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Eight zinc-plated breakaway lock nuts 5/16-18 thread

MIDWEST FASTENER CORP

MIDWEST FASTENER CORP 77783 Breakaway Lock Nut 5/16"-18 Zinc 8 PK

SKU CH-K4WS-4J1A5

Pack of eight breakaway lock nuts with 5/16"-18 threads and zinc plating

  • Product typeNuts
  • Breakaway design prevents over-tightening during installation
  • 5/16"-18 thread fits matching bolts precisely
  • Zinc plating resists corrosion in harsh environments
  • Eight-piece pack covers multiple fastening points
  • Manufacturer-direct supply ensures consistent quality control

Breakaway Lock Nut 5/16"-18 Zinc 8 PK

The Midwest Fastener Corp 77783 is a breakaway lock nut with a 5/16"-18 thread size and zinc-plated finish. It is supplied in a pack of eight pieces for fastening applications where a permanent, tamper-resistant joint is required. The nut features a breakaway head design that shears off at a predetermined torque, leaving a tamper-proof cone.

Mechanics needing permanent tamper-resistant

This pack suits mechanics and maintenance crews who need a fastener that cannot be removed with standard tools after installation. It is not for assemblies requiring routine disassembly or adjustment, nor for applications where a reusable locking nut is specified. Buyers needing a different thread pitch or a non-breakaway locking style should look at other hardware.

5/16"-18 thread with breakaway shear head

The critical specification is the 5/16"-18 thread combined with the breakaway shear-head mechanism. This thread size must match the mating bolt or stud exactly for the shear function to operate correctly. Verify the thread requirement before purchase because an incorrect pitch will prevent the nut from engaging or shearing as designed.

How it compares

Measured against everything we stock in General Hardware & Accessories, at today’s prices. Recalculated every night.

Price $26.99
Pricier than about 59% of the 2,607 comparable items (median $18.99).

Specifications

Product
Brand nameMIDWEST FASTENER
Product typeNuts

Questions about this item

What thread size bolt does the 5/16"-18 breakaway lock nut fit?

It fits a 5/16"-18 thread bolt, which has an 18 threads-per-inch pitch.

Can these zinc-plated nuts be used with existing Grade 5 or Grade 8 bolts?

Yes, the zinc plating provides corrosion resistance compatible with standard graded bolts.

How do I confirm the breakaway feature has engaged after tightening?

The hex section will shear off at the designed torque, leaving the conical locking portion permanently secured.

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