Nyloc Nut

How nyloc nuts lock

A nyloc nut has a thin ring of nylon inside the top of the nut. The ring is not threaded: the bolt forms a thread in it as the nut goes on, and the grip of the nylon on the bolt adds friction that resists the nut working loose under vibration. That resistance is called prevailing torque.

Nyloc nuts are one kind of prevailing torque lock nut; cone lock and other all-metal lock nuts are another. Hobson's anti-vibration paper notes that nyloc nuts suit joints that do not need a large preload, and that a standard nylon ring is not for joints exposed to high temperatures. Hobson's HUP brown ring data sheet gives -40 to +120°C for a standard ring and -40 to +230°C for the brown ring.

Nyloc nut types

• •Standard nyloc nut: the everyday full height nut, DIN 985 in metric, M2.5 to M64 and #4 to 2 inch.
• •Neptune 316 stainless (DIN 985, A4-80): high tensile stainless nyloc nuts, M4 to M36.
• •Thin nyloc nut: a lower nut for tight spaces. Metric thin nuts are ISO 10511 class 04 in M10 to M36, made for use with class 4.6 bolts; an M10 is 8.5mm high. Imperial thin nuts are zinc plated grade 2 or 304 stainless.
• •Heavy nyloc nut: a taller nut. The DIN 982 heavy nuts (class 8 from M6 to M20, class 10 from M12 to M20) are 11.5mm high in M10, against 10mm for a standard nut, and there are DIN 6924 class 8 heavy nuts in M10 and M12.
• •Hex flange nyloc nut (DIN 6926, no serrations): a built-in flange spreads the load like a washer. 304 stainless M4 to M16, zinc plated class 8 M6 to M12, and zinc yellow class 10 M12 to M24 for mining, agricultural equipment, general engineering, automotive and forklift work.
• •Dome nyloc nut (DIN 986): 304 stainless with a closed dome over the bolt end, M5 to M12.
• •HUP brown ring nyloc nut (ISO 7040): a temperature resistant nylon ring for -40 to +230°C, in zinc flake class 8 and 10 and 304 stainless A2-70, for mining and processing, rail and transport, energy, military and industrial work.

Classes, grades and finishes

The nylon itself copes outdoors: Hobson notes that long exposure to sun and salt may damage the ring, but in most conditions it still holds its prevailing torque, so nyloc nuts suit outdoor and marine work as long as the steel finish suits the site. A nut that has had long, harsh exposure should not be reused.

• •Class 6, 8 and 10 (metric steel): Hobson's tightening torque sheets work the clamp load for class 6 nyloc nuts on a class 4.6 bolt, class 8 on an 8.8 bolt and class 10 on a 10.9 bolt.
• •Grade 2, 5 and 8: the imperial steel nuts, all zinc plated except a mechanically galvanised grade 2 1/2 inch BSW.
• •Zinc plated: a 5 micron zinc coating with a clear passivate, for indoor and non-corrosive conditions.
• •Zinc yellow passivate: 5 micron zinc with a yellow passivate, more corrosion resistant than zinc plated, for low corrosion conditions or temporary fixing.
• •Mechanically galvanised: a 50 micron coating with high corrosion resistance, similar to hot dip galvanising, with better abrasion resistance and no risk of hydrogen embrittlement.
• •Zinc flake silver: a 10 micron coating with high corrosion resistance and no risk of hydrogen embrittlement (the brown ring nuts).
• •304 and 316 stainless: 316 has molybdenum added for better resistance near the sea. Neither 304 nor 316 is made to sit in seawater, and even 316 can visibly corrode where salt spray is left to build up.

Metric nyloc nut sizes

Every metric nyloc nut we carry. The size is the thread diameter (M10 fits a 10mm bolt) and the pitch is the distance between threads; coarse pitch is the everyday thread. Select a size to open it in the selector.

Imperial nyloc nut sizes: UNC, UNF and BSW

Imperial nuts are sized by the bolt diameter in inches (or gauge number for the smallest) and threads per inch (TPI). UNC is the coarse thread and UNF the fine; BSW is the older British Whitworth thread. Check the bolt before you order, as the threads do not mix.

Nyloc nut torque and tightening

Standard torque tables are not right for a nyloc nut. Part of the torque goes into turning the nut against the nylon, and none of that tightens the bolt, so add the prevailing torque to the target torque. The values below come from Hobson's tightening torque sheets and already include it. They are for DIN 985 steel nyloc nuts only: zinc plated, zinc yellow and mechanically galvanised, class 6, 8 and 10. Hobson gives no torque values for 304 or 316 stainless, Neptune, thin, heavy (DIN 982), flange or HUP brown ring nyloc nuts.

1. Use a bolt long enough for at least one full thread to stand out past the nut.
2. Run the nut on at a slow speed and keep impact tools off it: Hobson's thin nyloc nut sheet says impact tools should not be used and a slow speed avoids displacing the nylon ring.
3. Tighten to the torque for the class, finish and size; zinc plated values also apply to zinc yellow.
4. Nyloc nuts can be reused, but every use lowers the prevailing torque. Check it with a torque wrench before reusing a nut.

Nyloc nuts in Adelaide

Allmat supplies nyloc nuts, bolts, washers and threaded rod to builders, fabricators, mechanics and trade across Adelaide and South Australia. Add the nuts to a quote with the bolts and washers they go on, and we will price the lot.

Questions