Lock Nuts
What Are Lock Nuts?
Lock nuts are hex or slotted nuts engineered to resist loosening from vibration, shock, and temperature cycling. They maintain clamp load using prevailing torque (nylon insert or all-metal deformation), serrations, or a positive mechanical stop like a cotter pin.
Benefits of Lock Nuts
- Vibration resistance – helps keep joints tight under dynamic loads.
- Serviceable locking – mechanical solutions without permanent adhesives.
- Multiple mechanisms – nylon insert, all-metal prevailing torque, serrated faces, or cotter-pin lock.
- Environment coverage – options for high heat, chemicals, marine/salt, or indoor use.
Lock Nuts vs Standard Nuts — What’s the Difference?
Standard nuts rely only on thread friction; lock nuts add a locking feature: nylon collars, deformed threads, serrations, or a cotter pin through slots (castle nuts) to resist back-off.
Lock Nuts Sizes, Threads & Materials
- Threads: Match diameter and pitch (e.g., 1/4"-20, 3/8"-16, M8-1.25).
- Materials: 18-8 (304) stainless for general outdoor; 316 for marine/chlorides; zinc-plated steel for indoor; all-metal styles for high temps/chemicals.
- Strength: Pair nut property class/grade with the bolt and application requirements.
Installation Tips for Lock Nuts
- Verify exact diameter and pitch; start by hand to avoid cross-threading.
- Tighten to specified torque for the bolt size/grade and material stack.
- Jam-nut method: torque the primary nut, then hold it while tightening the jam nut against it.
- Castle nuts: torque, align a slot with the bolt hole, insert a new cotter pin, and bend to secure.
Common Applications for Lock Nuts
- Machinery, conveyors, rotating equipment
- Automotive, powersports, agricultural equipment
- Construction hardware and structural assemblies
- Marine and outdoor fixtures (with stainless materials)
Maintenance & Reuse for Lock Nuts
Nylon insert nuts lose prevailing torque with reuse—replace when resistance fades or the insert is worn. All-metal prevailing-torque nuts may be reused if torque remains within spec. Castle nuts are reusable; always replace cotter pins.
Lock Nuts FAQs
Quick answers to common lock-nut questions. If your use case isn’t covered, ask—we’ll recommend the right spec for your application.
It resists loosening from vibration and movement by adding friction (prevailing torque) or a mechanical stop (cotter pin), preserving clamp load.
Use all-metal for higher temperatures, chemical exposure, or frequent service; nylon insert for general duty below ~250°F (121°C).
Limited reuse is possible, but replace when the insert is worn or prevailing torque noticeably decreases.
Usually no. Lock nuts provide a mechanical lock; threadlocker is optional redundancy for severe vibration.
All-metal prevailing-torque (stover/two-way) or serrated cone styles. For a positive stop, use castle nuts with a cotter pin.
Follow specified torque for the bolt size/grade and materials. Under-torque reduces clamp; over-torque can damage threads or parts.
Match diameter and pitch exactly (e.g., 1/4"-20, M8-1.25) and choose a material/grade that suits load, temperature, and environment.
18-8 can be slightly magnetic after cold-working; 316 is typically less magnetic and offers better corrosion resistance.