"Weld Bolt" Means Two Different Problems
Half the people searching this term want a fastener designed to be welded on; the other half are holding a grade 8.8 hex bolt and wondering if they can weld it to a frame. Both land here on purpose — because the answer to the second problem is usually the first one:
You need a weld-on fastener
Projection weld bolts, weld studs, tab bolts, threaded bosses — a stud or thread that becomes part of the fabrication. We machine them in the sizes and materials catalogs don't stock.
You want to weld a standard bolt
If it's class 8.8/10.9, don't — welding heat destroys the quench-and-temper right at the joint. The sound route is a purpose-made bolt in weldable steel, sized up to carry the load. That's what we make.
Weld Fastener Types We Machine
| Type | What it does | Where catalogs run out |
|---|---|---|
| Projection weld bolts | Pilot locates in the hole, weld lugs fuse under resistance welding | Stainless, metric fine threads, long or stepped shanks |
| Weld studs (arc / CD blanks) | Stud welded to plate; thread stands proud for assembly | Odd lengths, large diameters, 316L and duplex |
| Tab & plate weld bolts | Flat tab MIG/TIG-welded into fabrications and frames | Custom tab shapes, heavy sections, imperial threads |
| Threaded weld bosses & bungs | Internally threaded boss welded into tube or sheet | Non-catalog threads (BSP, fine metric), exact standoff heights |
| Weld nuts, machined | Nut counterpart, matched material and pitch | Anything beyond common zinc-plated low-carbon sizes |
Every type is turned or milled from bar to your print — or measured from the old fastener if the original supplier is gone, the same way we handle any replacement bolt from a sample.
Which Steels Actually Weld — an Honest Table
Weldability is decided by the material, not by wishing. This is the guidance we apply when quoting:
| Material | Weldability | Notes for the joint |
|---|---|---|
| Low-carbon steel (C1010/C1020, S235/A36) | Excellent | The standard weld-fastener material — resistance, arc and MIG/TIG all fine |
| 304 / 316 stainless | Good | Use matching filler; L grades (316L) resist carbide sensitization at the weld |
| A2-70 / A4-70 bolt grades | Weldable with care | Cold-worked strength drops in the heat-affected zone — size accordingly |
| Class 8.8 / 10.9 / 12.9 | Do not weld | Quench-and-temper strength is destroyed by welding heat; joint can turn brittle |
| Medium/high-carbon & alloy steel (C45, 42CrMo4) | Not without preheat/PWHT | Cracking risk; if the design forces it, talk to us about geometry instead |
The engineering answer to "can I weld a high-tensile bolt?" is to change the part, not the process: a purpose-machined weld bolt in low-carbon steel, one or two sizes up in diameter, carries the load without gambling a welded joint on tempered steel. Tell us the load and we'll size it with you.
The Jobs That Land on Our Bench
"We need twenty M10 projection weld bolts in 316 — every catalog stocks only plain steel."
Stainless weld fasteners are a made-to-order item almost everywhere. We machine them from 316L bar with the pilot and lug geometry your resistance welder needs, in three weeks, with a material certificate.
"Threaded bosses to weld into a tube frame — M12×1.25 fine, exact 18 mm standoff."
Weld bungs and bosses in odd threads and exact heights are a lathe job, not a catalog search. Chamfered weld edge, machined seat, any thread we can gauge — including non-standard threads.
"The weld studs on our conveyor panels are obsolete — supplier gone, thread unknown."
Send one old stud, even worn. We gauge the thread, measure the weld end, and reproduce it — plus spares in the same run. No drawing needed.
Specs & What We Hold
- Threads: metric coarse and fine, UNC/UNF, BSP — gauged to ISO 965 6g or your imperial class
- Sizes: M4 to M36 typical for weld fasteners (larger — see large bolts)
- Weld geometry to your process: projection lug count and height, CD tip, chamfered bung edges
- Materials certified: EN 10204 3.1 certificate traceable to bar heat, on request
- Finish: plain (best for welding), or post-weld-appropriate coatings on request — we'll flag anything (zinc!) that shouldn't go near an arc
Frequently Asked Questions
You shouldn't — welding heat destroys the quench-and-temper where the joint needs it most. The sound route is a purpose-machined bolt in weldable low-carbon steel, sized up for the load. That's what this page is for.
Yes — 304 and 316/316L, machined from bar with matching weld geometry. Catalog weld fasteners are overwhelmingly plain low-carbon steel, so stainless is a normal made-to-order job for us, from one piece.
Projection weld bolts, arc/CD weld studs, tab and plate weld bolts, threaded weld bosses and bungs, and matching machined weld nuts — metric, UNC/UNF and fine pitches.
One piece. Cold-formed catalog weld bolts make sense by the thousand; machining from bar makes sense from one to a few hundred — no tooling, no minimum.
A drawing, dimensioned sketch or the old fastener, plus the base material and welding process (MIG/TIG, resistance, arc stud). We confirm material and geometry before machining. Quote in 24 hours.
Get Weld Bolts Quoted
Drawing, sketch or the old fastener. Engineers reply in 24h.
// Qty & price
1 pc
Sample price
Confirm fit before a run
3–50
Unit price drops
Setup cost shared
50+
Best price
All tiers quoted upfront
- →No distributor — you pay the maker directly
- →CAD saved after first order — reorder anytime at lower unit price