Weld Nut

What a weld nut is

A weld nut is a nut made to be welded on. Once it is welded to sheet metal, a panel or a bracket, the part carries its own thread, and a bolt or machine screw can be fitted later from the other side without anyone holding a nut. That helps where the back of the panel cannot be reached once the job is assembled.

Ours are hex weld nuts to DIN 929 in 304 (A2) stainless steel. As the product photo shows, a DIN 929 nut has a raised pilot collar on one face, which locates the nut in a hole in the sheet, and small projections on the corners of that face, which are what touch the sheet when the nut is projection (resistance) welded.

Hobson publishes no welding procedure or hole sizes for these nuts in the documents we have, so weld them to your shop's procedure for stainless steel.

Choosing weldable nuts

• •Thread size: match the bolt or screw, M3 to M8.
• •Thread pitch: all metric coarse, from 0.50mm (M3) to 1.25mm (M8).
• •Material: 304 (A2) stainless steel, for stainless sheet, panels and brackets.
• •Can't weld, or only have access from one side? A rivet nut gives thin sheet a thread and is set from the front with a rivet nut tool.

Weld nut sizes

Select a size to open it in the selector.

304 stainless: where it suits

A2 is the fastener grade for the 304 group of stainless steels. Hobson's chemistry table gives A2 as 17 to 20% chromium and 8 to 13% nickel, and A4 (316) as 16 to 18.5% chromium, 10 to 14% nickel and 2 to 3% molybdenum.

Hobson's corrosion guide for metal connectors lists 304 or 316 stainless for work exposed to the weather in most zones, but 316 only within 2m of a pool edge. Neither 304 nor 316 is made to sit in seawater, per the stainless steel article Hobson publishes.

The same article says rust that appears on stainless within days or weeks is almost certainly carbon steel contamination from fabrication or the local environment, so keep stainless work clear of steel grinding dust and tools used on mild steel.

Fitting a weld nut and the bolt that goes in it

1. Make a hole in the sheet to suit the pilot collar, so the nut sits square.
2. Locate the nut with its projections against the sheet and weld it to your procedure.
3. Keep weld spatter out of the thread and check the thread runs freely before assembly.
4. Stainless bolts in stainless nuts can gall (cold weld) as they tighten. Hobson's galling sheet suggests slowing the installation speed and lubricating the threads with a lubricant containing molybdenum disulphide. The stainless steel article Hobson publishes says swapping grades (such as a 316 nut on a 304 bolt) is not a reliable fix: galling is worse with fine threads, tight clearances, poor thread profiles, no lubrication, dirt and over-tightening.

Weld nuts in Adelaide

Allmat supplies weld nuts, rivet nuts and stainless fasteners to fabricators, sheet metal workers, shopfitters and trade across Adelaide and South Australia. Add them to a quote with the screws they take, and we will price the lot.

Questions