The shop recently acquired a TIG welder and the rep was describing a form of spot welding called Dot welding, used by tool and die makers predominately to repair pits and imperfections in molds and stamping dies. In use a small dot or ball of appropriate metal is placed in the pit and a high amperage/low voltage electrode is placed against it. The welder is triggered and the molten bead is fused in the pit without the shrinkage from conventional welding. We get a lot of guns in with pitting in non-critical areas. Anyone ever use this method for pitting repair? If so what were your experiences?

We have a member that does a lot of mold repair.

Hopefully he chimes in.

Of course I have, albeit the technique as described by your rep will result in disaster. In TIG welding, the Tungsten (I use Thorium) electrodes must NEVER touch anything. If you do, you will contaminate the work and ruin the tip. You just regrind those.
You must activate the TIG arc with your foot pedal; it will melt the surface, and whatever filler material you place in it. Just as easy is to feed a bit of rod into it, as usual. MIG welding is the same, and with that, the wire is automatically fed into the pit. Come over and I'll show you.
Not sure what conventional welding is; but TIG and MIG are conventional now. I have not used ARC or gas for decades.

good stuff, works as advertised, takes a bit of a learning curve to get it right, you need a dual pulse machine to get good clean welds.

One can do a similar thing with a piece of welding rod...drill a hole into the imperfection, drive in a piece of welding rod, cut off close and simply melt in place.

Yes, however, a true Dot welding machine is nothing like a TIG welder.

OP,
Find yourself a competent jeweler w/ a laser welder to blend out pits.

Your welding rep hasn't the slightest clue of any TIG processes.

As mentioned you need a puddle or you are attempting TIG spot welding....prep the cup or you'll have a mess to repair.

Thanks Dan, will do.

quote:

Originally posted by Dans40XC:
OP,
Find yourself a competent jeweler w/ a laser welder to blend out pits.

Your welding rep hasn't the slightest clue of any TIG processes.

As mentioned you need a puddle or you are attempting TIG spot welding....prep the cup or you'll have a mess to repair.

Yep
I've used the fusion arc dot weld process of TiG welding under a microscope for a long time.

We have 3 micro welders
One LazeOne fusion arc
One LazeOne mold mender
One Micro TiG
All three with 25x microscopes

Find yourself a good spur and bit maker, they use what they call dot welds for decoration...Very nice work...

I fill pits with a laser welder. Works great.

it works very well but only f the guy doing itg knows what he's going - otherwise there's always bondo

quote:

Originally posted by butchloc:
it works very well but only f the guy doing itg knows what he's going - otherwise there's always bondo

So can bondo be rust blued?