CuW Guide Pin for Vacuum Interrupters
In vacuum interrupter assemblies, guide pins control the moving contact's travel path and prevent rotation during opening and closing.
Copper tungsten pins are mostly a copper body with a CuW tip on the working face — tungsten only where the arc or the spark lands, because CuW costs several times what copper does. We join the tip three ways: one-piece sintered, friction welded, or brazed. We do not cast-on and we do not electron-beam weld. Guide pins for vacuum interrupter assemblies, domed and slotted contact pins, and solid CuW pins turned from rod, in CuW70 and CuW80 (CuW75 on request), machined to drawing. EDM and resistance welding electrode pins use the same material and production route and are quoted from your print — we do not carry them as catalogue items.
In vacuum interrupter assemblies, guide pins control the moving contact's travel path and prevent rotation during opening and closing.
Most copper tungsten pins are not solid CuW. They are a copper body with a CuW tip on the working face, because CuW costs several times what copper does and only the last few millimetres see the arc or the spark. How that tip is joined is part of the specification, not a detail. It sets joint strength, the temperature the joint will take, and whether there is a filler layer sitting in the current path.
| Route | What it is | Where we use it |
|---|---|---|
| One-piece sintered | The whole pin pressed, sintered and copper-infiltrated as a single CuW part, then machined | Small pins, and anything where the full length is under duty. No joint to fail |
| Friction welded | CuW and copper joined by rotating one against the other under axial load. No filler metal, no intermediate layer | Round sections where full joint strength matters and a brazed seam is not wanted in the current path |
| Brazed | CuW tip brazed to the copper body with a filler alloy | The general case — most tip geometries, most sizes |
We do not cast-on and we do not electron-beam weld. Those are the other two routes used on high-voltage arcing contacts, and if your drawing calls for either, say so at enquiry rather than after the order — we would be quoting a process change, not a price.
If the drawing does not specify a route, tell us what the pin does and the size, and we will say which one we would run and why.
| Form | Construction | Where it goes |
|---|---|---|
| Guide pin | Threaded stud, copper body with a cross hole, CuW ring on the end face | Vacuum interrupter assemblies — controls the moving contact's travel and stops it rotating |
| Domed-tip contact pin | Flanged threaded stud, copper shank, CuW dome | Make-and-break contact where the arc lands on a small radiused face |
| Slotted-tip contact pin | Flanged stud, copper shank, split CuW tip | Plug-in contact that has to give slightly on insertion |
| Solid pin, CuW tip | Small one-piece pin with a CuW dome, no flange | Where there is no room for a flange or a brazed joint of any size |
| Solid CuW pin | Turned from CuW rod throughout | Whole length under arc or spark duty, or too small to braze |
Tipped construction is cheaper than solid CuW on anything above a few millimetres of tip, which is most of this list. Below that the joint costs more than the tungsten it saves, and the pin is made one-piece. Brazing CuW to copper covers the filler choice and the wetting problem the tungsten skeleton creates on the brazed route.
| Grade | Tungsten | Use |
|---|---|---|
| CuW70 | 70 wt% | The default, and with CuW80 the grade most drawings actually call for |
| CuW75 | 75 wt% | Available, less often specified. Between the two above |
| CuW80 | 80 wt% | The other grade in common use. Severe duty, and fine detail that has to hold its shape — accept the conductivity penalty deliberately |
Across the range, conductivity runs roughly 32–45% IACS and hardness roughly HB 175–240, both tracking tungsten content (ASTM B702 typical values). More tungsten buys erosion resistance and costs conductivity; there is no grade that gives you both. Choosing a CuW grade works through it, and the properties guide has the full data.
The material and the production route are the same — press, sinter, infiltrate, then CNC turn and grind — so electrode pins are within what we build. We quote them from your drawing.
We do not carry them as catalogue items. Our standard range is medium-voltage switchgear parts, and electrode work is made to print rather than picked off a shelf. If you want a standard electrode from a stock list, a specialist electrode supplier will serve you faster. If you want a specific geometry in a specific grade, in quantities a stockist will not tool up for, send the print.
CuW pins get specified three ways depending on who wrote the drawing. European and Chinese prints usually give the composite grade directly — CuW70, CuW75, CuW80. North American EDM and welding prints often give an ASTM B702 class instead. And plenty of drawings still carry a proprietary trade designation from whichever supplier the part was first bought from.
All three describe the same tungsten weight percentage. Send whichever is on your drawing and we confirm the equivalent grade before quoting rather than assuming a cross-reference. Where a drawing carries another manufacturer's trade name, we quote the equivalent CuW grade and supply it under its own designation.
A drawing, the quantity, and what the pin does. The last one matters: two pins with identical dimensions want different grades and different constructions depending on whether the tip sees an arc, a spark, or only sliding wear.
Yes. Send the sample and say which dimensions are functional. If it is worn, tell us where — copying a worn pin reproduces the wear, and on a contact face that means reproducing the failure.
No to both. Our routes are one-piece sintered, friction welded, and brazed. If your existing part is cast-on or EB welded, send it anyway — in most pin geometries one of our three routes will meet the same requirement, and we will tell you plainly if it will not.
CuW is for arc and spark duty. A pin that only carries current and never arcs is cheaper and more conductive in plain copper. A contact sealed inside a vacuum bottle is CuCr, not CuW. The material comparison draws the boundaries.