Using tig for spot or plug welds

Ram48 · Thu Apr 16, 2015 11:40 am

Hello
I am a rookie hobby welder and would like some information on spot and plug welding with a tig.
The material will be 16,18 and 20ga sheet metal to any combination of each. ad will become part of an enclosure for a cnc mill.
Does it pay to buy one of those Spot welding cups?
My tig machine does have a "spot timer" on it.
Thanks for any help you can give me
Ray Mc

LtBadd · Thu Apr 16, 2015 6:56 pm

Ram48 wrote:Hello
I am a rookie hobby welder and would like some information on spot and plug welding with a tig.
The material will be 16,18 and 20ga sheet metal to any combination of each. ad will become part of an enclosure for a cnc mill.
Does it pay to buy one of those Spot welding cups?
My tig machine does have a "spot timer" on it.
Thanks for any help you can give me
Ray Mc

I've never seen or heard of a "spot welding cup", can you post a link?

rick9345 · Thu Apr 16, 2015 8:10 pm

http://www.eastwood.com/tig-spot-weld-kit.html

https://www.youtube.com/watch?v=3-LSuFsqoWc

CMSRacing · Thu Apr 16, 2015 10:51 pm

I can't say I have any experience with this setup, but I do have a few spot welders at the shop. The first thing I can tell you about spot welding is that everything needs to be clean and flat. Those clamps that come with the cups are probably more important than the cup its self. For spot welding to work you need to melt the top sheet into the bottom sheet. The test is, if you pull the sheets apart and you get a hole in the top sheet with a weld nugget on the bottom, you did it right. If the two sheets have a gap, it won't work. Unless this works differently from typical spot welders.
There are plenty of spot welds on your car, so won't say spot welding is worthless, but it can be a pain. The name of the game is power. My biggest spot welder is a 230v. It's ok for 20ga and up, but no way would I try 16ga.
If you don't feel comfortable welding the sheets, I would recommend rivets instead. What type of CNC is this going on? Is this for the controller housing? Desk top might be ok, but a big mill will shake apart any spot weld you try to make.

Fri Apr 17, 2015 2:38 am

To simplify things, forget the spot weld, with jigs and timers and clamps. Drill a 1/4" hole in the top piece and simply fuse the hole to the bottom plate. There's your plug weld.

motox · Fri Apr 17, 2015 5:37 am

i agree with mike
this method put very little heat into the
sheet metal if you alternate between holes.
craig

MinnesotaDave · Fri Apr 17, 2015 10:13 am

weldin mike 27 wrote:To simplify things, forget the spot weld, with jigs and timers and clamps. Drill a 1/4" hole in the top piece and simply fuse the hole to the bottom plate. There's your plug weld.

That's what I do with cars - but I mig it on cars - goes pretty quick.

Fri Apr 17, 2015 10:17 am

I am a fan of plug welds, with either process it's a great way to make a hidden weld, neat joint. That's like crouching tiger, hidden dragon.

kiwi2wheels · Fri Apr 17, 2015 11:14 am

You may find a Whitney Punch useful to make to the holes.

motox · Fri Apr 17, 2015 3:54 pm

yes punch, cleaner holes less burrs.
craig