Complete guide to nylon insert lock nuts, flange locking nuts, and vibration proof self locking nuts for automotive, machinery, and industrial applications.
Nylon Insert Lock Nuts (Nyloc): How They Work
Nylon insert lock nuts (commonly called Nyloc nuts, DIN 985 / ISO 10511) have a nylon collar inserted into the top of the nut that creates a friction lock against the bolt thread. When the bolt is installed, the nylon deforms around the thread roots, creating resistance to loosening. Factory supply of nylon insert lock nuts covers grades from Grade 6 to Grade 10 in both zinc-plated carbon steel and stainless steel (A2-70, A4-80). Temperature range: standard nylon inserts are rated to approximately 120°C; high-temperature nylon inserts (nylon 6/6 with heat stabilizers) extend this to 200°C. For mechanical equipment experiencing vibration (pumps, compressors, gearboxes), Nyloc nuts provide effective locking without special tools. The nylon insert is reusable up to 15-20 cycles before losing effectiveness.
High Strength Flange Locking Nuts
High strength flange locking nuts (DIN 6925 / EN 1665) combine the locking function of a nylon insert with the increased bearing area of a flange nut. The integrated flange (typically 1.5× the nut width across flats) distributes load over a larger母材 area, reducing the risk of母材 crushing and eliminating the need for a separate washer. The flange locking nut with serrated flange face provides additional vibration resistance through the serrations biting into the母材 surface. These nuts are the standard for automotive wheel hub connections (wheel nuts are flange locking nuts), suspension components, and any application where vibration-induced loosening is the primary failure mode. Available in Grade 8, 10, and 12 in zinc-plated carbon steel, and in A4-316 stainless for corrosion-critical applications.
Vibration Proof Self Locking Nuts for Automotive
Vibration proof self locking nuts for automotive applications are tested to specific vibration profiles defined in automotive standards (ISO 16130, AVL, or individual OEM specifications). Unlike general-purpose Nyloc nuts, automotive vibration proof locking nuts must maintain preload through temperature cycling (-40°C to +150°C), humidity exposure, and mechanical vibration testing. Round lock nuts with integrated stop washer (also called CADO nuts or castle nuts with cotter pin) use a slotted outer ring that accepts a cotter pin through the bolt for positive locking—this is the traditional method for securing wheel hub nuts, steering linkage, and other critical safety components where the nut absolutely cannot loosen. Always replace cotter pin nuts with new cotter pins at each service.
Lock Nut Type Selection Guide
| Lock Nut Type | Reusable | Temperature Limit | Vibration Resistance | Common Applications |
|---|---|---|---|---|
| Nylon Insert (Nyloc) | 15-20 times | 120°C (standard) | Good | General machinery, appliances |
| Nylon Insert (High Temp) | 10-15 times | 200°C | Good | Engines, exhaust, HVAC |
| All Metal Prevailing Torque | Yes (limited) | 650°C+ | Excellent | High temp, chemical, aerospace |
| Flange Locking (Serrated) | No | 200°C | Very Good | Automotive, wheel hubs, suspension |
| Castle Nut + Cotter Pin | Yes (with new pin) | No limit | Excellent (positive lock) | Wheel hubs, steering, critical safety |
| Lock Washer (Spring) | Yes | No limit | Moderate | Not recommended alone for vibration |
Frequently Asked Questions
Can nylon insert lock nuts be reused?
Yes, nylon insert nuts can be reused approximately 15-20 times before the nylon loses its grip. Mark or discard after extended reuse cycles.
What temperature do nylon insert nuts fail at?
Standard nylon insert nuts begin losing effectiveness above 120°C. High-temperature versions (with heat stabilizers) are good to 200°C.
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