Plug welds

[Dreamcar]

I've got a lot of new sheet metal to install and a local store has 5/16 air punch tools for a good price. Is this considerd the correct hole size for plug welds?

[Troy]

I just use a drill - and I have a punch! There are a million places that need a hole but are too far from the edge to use an air punch (think trunk pan, floor pans, etc.). If you're that close to the edge you might as well purchase a cheap spot welder. When I'm making a hole for something that needs to attach to a frame rail (ie thick) I use 3/8" holes. For attaching two pieces of sheet metal I'll go a little smaller because 3/8" is a fairly large space to cover when you can burn through so quickly. With a copper backer it's not as bad but then you have to keep moving it around too.

Troy

[tsmithae]

3/8" is my preferred size as well and I too use a drill. The hole punch is very limited, as Troy said.

[AZMoparboy]

Hi, I am a novice too, did a lot of reading on replacing metal on my 71 challenger body. I like everything Troy says, I used all of those techniques and found one other to help in areas that I couldn't clamp well. I used self tapping sheet metal screws to draw the metal together. Then after the plug welds were done I removed the screws and with just a little bump of the welder I closed the screw hole. This may not be a very professional way of doing it but for my project it worked great. Good luck

[Dreamcar]

Thanks

[fy469rtse]

Spend the money on a spot welder instead, just drill your plug holes,
You won't regret the spot welder, minimal clean up, no grinding , factory look , great for the person with minimal experience , although by the time you get to the end you will have better skills for the experience

[green69rt]

I second all the comments here.  Except I did buy the punch, just because drilling 200 holes (probably a low estimate) can take a lot of time.   Many of the holes are along an edge that the punch can reach.   The rest need a drill; or if you want a new toy for your shop get a spot welder.  Cheap spot welders won't reach everything either.   Seems to take a combination to get the job done.

Be careful of using the punch on curved surfaces as it can introduce stress ( read "oilcanning") into the metal,  same for flange tools.