Hex Nuts

The standard hexagon nut, to ISO 4032, DIN 934 and ASME B18.2.2. Every listing gives the across-flats dimension and the nut height in both millimetres and inches, so you know which wrench it takes before it arrives.

Across flats is the number that matters

Thread size does not tell you the wrench. An M4 nut takes a 7 mm wrench and an M5 takes 8 mm; the imperial equivalents are close but not identical, and a 5/16 inch wrench on an 8 mm nut will round the corners. Each product page states the figure in both systems.

Plain nuts do not stay put

A standard hex nut relies entirely on friction from the clamp load. Under vibration it will loosen. If the joint sees any cyclic load, use a nylon insert lock nut or add a split lock washer — a plain nut plus thread locker is a distant third choice.

Material

304 stainless. Stainless nut on a stainless bolt is the classic galling pair: run them together too fast and the threads weld. Slow down and use an anti-seize compound.