Nylon Insert Jam Nuts
What are Nylon Insert Jam Nuts?
Nylon insert jam nuts are thin, low-profile hex lock nuts that use a captive nylon ring to create prevailing torque on the bolt’s threads. They’re commonly used as a secondary “jam” nut or anywhere space is tight and a standard height lock nut won’t fit.
How do Nylon Insert Jam Nuts Work?
The nylon collar interferes slightly with the male thread to add friction that resists loosening from vibration and shock. Because jam nuts are thinner, they save space while still providing a clean, serviceable locking action without liquid threadlocker.
Benefits of Nylon Insert Jam Nuts
- Low profile: Fits in tight clearances where standard lock nuts are too tall.
- Vibration resistance: Prevailing torque helps maintain clamp load.
- Clean & re-serviceable: No adhesive cure time or residue.
- Thread friendly: Nylon is gentler on coated or plated fasteners.
Common Applications for Nylon Insert Jam Nuts
- Locking against a primary nut in assemblies and linkages
- Machinery guards, conveyors, and material handling
- Automotive, powersports, and equipment panels
- Outdoor projects (choose stainless as needed)
Nylon Insert Jam Nuts — Materials & Sizing
- Threads: Match diameter & pitch exactly (e.g., 1/4"-20, 3/8"-16, M8-1.25).
- Materials: 18-8/304 stainless for general outdoor use; 316 stainless for marine/chlorides; zinc-plated carbon steel for dry indoor use.
- Strength pairing: Choose nut material/grade to suit the bolt grade and service loads.
- Temperature note: Nylon inserts perform best below ~250°F (121°C). For higher temperatures, use all-metal prevailing-torque lock nuts.
Installation Tips for Nylon Insert Jam Nuts
- Start by hand to avoid cross-threading, then finish with the proper wrench or driver.
- If using the jam method: tighten the primary nut to torque first, then snug the jam nut against it while holding the primary nut to avoid under-torque.
- Ensure 2–3 full threads extend past the nylon ring after tightening so the insert fully engages.
- Avoid lubricants on the nylon; they can reduce prevailing torque.
Are Nylon Insert Jam Nuts Reusable?
Limited reuse is possible, but the nylon ring loses prevailing torque with each cycle. Replace the nut if resistance feels weak, the insert is worn, or the joint is safety-critical.
Nylon Insert Jam Nuts FAQs
See the quick answers below for sizing, installation, temperature, and reuse guidance.
To provide a low-profile, vibration-resistant lock where space is limited or as a secondary “jam” nut against a primary nut.
Tighten to the specified torque for the bolt size/grade. If using the jam method, torque the primary nut first, then snug the jam nut against it while holding the primary nut.
A few times, but replace if prevailing torque drops, the nylon insert is damaged, or the application is safety-critical.
Typically up to ~250°F (121°C). For higher temperatures, choose an all-metal prevailing-torque lock nut.
Zinc-plated steel for dry indoor use; 18-8/304 stainless for general outdoor; 316 stainless for marine or chloride exposure.
Not for locking. A flat washer can help spread load on soft materials or oversized holes.
The insert may not be fully engaged. Use a longer bolt or reduce stack height so 2–3 full threads extend past the nylon ring.