Prevailing Torque, Nylon Patches or Deformed Threads: Picking a Locking Method
Every anti-loosening method buys security with some trade-off. The trick is matching the trade-off to your service environment.
Bottom line: for most Anti-Loosening Series applications the decision comes down to load, environment and assembly method — the Anti-Loosening Series guide walks through the selection.
Nylon patch screws (pre-applied)
A nylon patch in the thread creates strong prevailing torque cheaply and suits M2–M12 consumer and automotive hardware. Its limits: 120 °C continuous temperature, sensitivity to oil on installation, and a finite reassembly count — typically two or three before the patch is spent.
All-metal prevailing torque
Deformed-thread screws, serrated flanges and locking inserts survive 300 °C+, shrug off solvents and keep locking through many assembly cycles. They cost more than patches and add installation torque, which must be budgeted into your torque spec.
Positive locking
Cotter pins, lock wire and keyed inserts do not rely on friction at all — they physically prevent rotation. For safety-critical flight and rail hardware, this is the specification answer when friction methods are not certifiable.
The decision matrix
Temperature first, then reassembly count, then vibration severity, then cost. Toprecision manufactures patch-screws in-house and also offers all-metal locking fasteners, so we can quote both variants of the same drawing and let test data decide — no specification lock-in.
Anti-loosening methods under transverse vibration
| Method | Preload retained after 1000 cycles | Reusable | Cost |
|---|---|---|---|
| Plain nut (no lock) | <5% | Yes | Low |
| Spring lock washer | <3% (worse than plain) | Yes | Low |
| Nylon insert nut (NYLOC) | ~40% | Limited (5x) | Medium |
| All-metal prevailing torque | ~55% | Yes | Medium |
| Wedge lock washer (Nord-Lock) | ~85% | Yes | High |
| Pre-applied thread locker | >95% | Limited | Medium |
Need a vibration-proof fastener solution?
Toprecision supplies prevailing-torque lock nuts, nylon-insert nuts, wedge lock washers and pre-applied thread-locking patches for EV powertrains, rail and vibrating machinery. Send the vibration frequency and clamp load requirement — we will recommend the locking method and supply Junker test data. Request anti-loosening consult.
When Nylon Patches Fail
Nylon patch locking works by friction, not by positive locking. At temperatures above 120 °C, the nylon softens and loses its gripping force. In high-vibration or high-temperature environments, use deformed-thread or all-metal locking instead. Also note: nylon patches are single-use. Re-installing a screw with a used nylon patch reduces the prevailing torque by 40–60% because the nylon has already deformed around the threads.
