A weld nut is a plain nut with projections that melt: the projections carry the welding current, collapse under the electrode and become the joint. DIN 929 gives the hex form, DIN 928 the square one; both stop at M12 and M24 and both assume plain steel. The nut that is stainless, fine-pitched, taller or piloted differently is the one that gets made.
EKINSUN LTD is a custom parts manufacturer that machines weld nuts to drawing: a non-standard height, a fine or left-hand pitch, a pilot sized to your hole, a 304 or 316L body, or projections placed for your electrode. The stock ranges below come from a 2026 catalogue; the process table says which nut form suits which welding process, and the negative-space table shows the border between buying and making.
"The frame is 304 and the nut must be 304 too, M10 fine, with a pilot for the 11 mm hole. The catalogue has M10 coarse in plain steel and nothing else."
Stainless, fine pitch, pilot: three conditions, each one enough on its own.
| Form | Standard | Stock range | Stock materials | Notes |
|---|---|---|---|---|
| Hex weld nut, three projections | DIN 929 | M3–M12 | plain steel; 304 stainless | with or without pilot; the general-purpose nut for brackets and frames |
| Square weld nut, four projections | DIN 928 | M3–M24 | plain steel; 304 stainless | larger weld area; the nut for thicker sheet and higher load |
| Round weld nut with pilot | maker series | M4–M12 | plain steel | the pilot locates the nut in the hole before welding |
| Flanged weld nut | maker series | M6–M12 | plain steel | flange spreads the load and hides a rough hole |
| Hex weld nut without projections (arc weld) | DIN 929 form, plain base | M3–M10 | plain steel | for MIG / TIG fillet welding around the base |
| Weld stud / spot-weld screw | ISO 13918 | M2.5–M10 | copper-plated steel, 304, aluminium | the male counterpart — see weld bolts and studs |
| Process | Nut form | Material and finish | Why |
|---|---|---|---|
| Resistance projection welding (press welder) | hex DIN 929 or square DIN 928 with projections | plain, unplated low-carbon steel; 304 for stainless sheet | the projections concentrate the current; plating contaminates the weld and the electrode |
| Spot welding with a hand gun | round or hex with pilot, three projections | plain steel | the pilot keeps the nut on the hole while the gun comes in |
| MIG / TIG arc welding | nut without projections, or a flanged nut | plain steel; 304 / 316L for stainless | a fillet around the base, so projections are not wanted |
| Welding onto a coated or painted frame | — | — | weld before coating, or use a rivet nut or a clinch nut instead |
| Aluminium frame | — | — | steel weld nuts do not weld to aluminium; use a rivet nut, a clinch nut or an aluminium weld stud |
Read the pitch before you order the weld nut. Lay a steel rule along ten thread crests and divide by ten: 10 mm over ten pitches is a 1 mm pitch (M6 coarse), 12.5 mm is M8 coarse, 15 mm is M10 coarse, 17.5 mm is M12 coarse. A reading that is not a round number of millimetres is an inch thread, and a reading that is shorter than the coarse pitch for that diameter is a fine thread. If diameter, pitch and the size range in the table all agree, buy the stock part. If any of the three is off the shelf, that is the one we make. The full measuring routine, including the inch traps →
| What you need | In the catalogue? | What we make |
|---|---|---|
| Hex DIN 929 M3–M12 or square DIN 928 M3–M24 in plain steel | Yes | Buy it from stock. No one-off competes with a pressed weld nut. |
| The same in 304 stainless, M3–M12 hex or M3–M24 square | Yes | Stocked; buy it. |
| A weld nut in 316L / 1.4404 | No | Machined from 316L bar with projections milled or formed on the base. |
| A fine-pitch or left-hand weld nut — M10×1.25, M12×1.5, M16 LH | No | Tapped or single-pointed to your reading; the base and projections stay DIN. |
| A pilot sized to an existing hole, or a longer pilot for thick sheet | No | Turned to your hole; pilot length to your sheet. |
| A height above or below DIN, or a reduced across-flats for a tight pocket | No | Machined; the projections are placed for your electrode. |
| A weld nut above M24 | No | Turned from bar; projection or plain base. |
| A weld nut in aluminium 6061 or 7075 for an aluminium frame | No | Not a weld nut: aluminium needs a rivet nut, a clinch nut or an aluminium weld stud, and we say so instead of quoting the wrong part. |
| Material | Designation | Where it fits here |
|---|---|---|
| Low-carbon steel, plain | S235 / 1010 class | the weld nut: unplated, so the weld is clean |
| Stainless 304 | 1.4301 / A2 | stocked hex and square weld nuts for 304 frames |
| Stainless 316L | 1.4404 / A4 | machined to order for marine and chemical frames |
| Free-machining stainless | 303 / 1.4305 | not for welding; listed so it is not specified by mistake |
| Aluminium 6061 | AlMg1SiCu | the frame alloy that needs a rivet nut or clinch nut instead of a weld nut |
| Aluminium 7075 | AlZn5.5MgCu | as above; not weldable with steel nuts |
Zinc on the projections vaporises in the weld, contaminates the joint, pits the electrode and gives an inconsistent weld. Weld nuts are supplied plain and the assembly is plated or painted afterwards.
Hex DIN 929 has three projections and suits general brackets and frames; square DIN 928 has four projections and a larger weld area, so it takes thicker sheet and higher load, and it is stocked to M24 where the hex form stops at M12.
Yes, with a 304 weld nut on a 304 frame; the stock range covers M3–M12 hex and M3–M24 square. For 316L frames the nut is machined in 316L so the joint stays a single alloy.
The pilot is a short spigot that sits in the sheet hole and locates the nut before the electrode comes down. Its diameter must match the hole, which is why a nut with a pilot for a non-standard hole is made rather than bought.
EKINSUN LTD is a custom parts manufacturer that machines weld nuts in plain steel, 304 and 316L with the pitch, height, pilot and projection pattern the drawing calls for, from 1 piece, with a quote within 12 hours.
No list price. The drivers are material, pitch, whether a pilot or a non-standard height is machined, and quantity. A batch of steel nuts with a special pilot costs little more than the tapping; a single 316L fine-pitch nut is a turned part and priced as one. The quote states the drivers.
Thread and pitch, sheet material and thickness, hole diameter, height or across-flats if they matter, projection pattern, quantity. From 1 piece, quote within 12 hours.
Weld nuts machined to pitch, height, pilot and material — from 1 piece, quote in 12 hours.