Backing for plug welds ???

[Crazy Horse]

I've been working on some outer rims here, found some good replacements but I had to remove the center area of the rims which were riveted in. As a result, I have what I need but I have to plug weld the rivet holes with my mig welder. Someone told me I should back the hole with something that the weld wouldn't adhere to and it would make a neater job with less grinding later. Somewhere I think I heard that copper would work. I was also thinking of maybe a rock (stone), brick, or something like that. Anybody done this and had luck with it?

 

[el6147]

copper will work very well.

 

[UncleTom]

copper, carbon

 

[ericlb]

it needs to be a metal some types of rock, welding heat can cause to explode or at the very least contaminate the weld, use brass or bronze for a backing plate, ive also used a 4lb hammer one time , and it worked, but that was because i was 5 miles from the house and its what i had available to use at the time

 

[jon f mn]

Don't try rock or stone, it will get in the weld. Copper or brass will, but I wonder why? If you are using wirefeed with gas you shouldn't need it. Just weld both sides and there should be little need for grinding. A well rounded bump inside won't hurt anything, just make sure nothing is sharp.

 

[tbish]

use brass or copper the heat is likely to cause the stone to pop or explode

 

[gitrib]

If you are using a mig wire feed you do not need a back up.Just weld on both sides and grind smooth. Just go round and round with your arc. gitrib

 

[mkirsch]

I bought a copper welding spoon at Harbor Freight for just such a purpose. Has a big curved copper plate attached to an insulated handle.

 

[JMS/.MN]

Remember the carbon arc attachment for a stick welder. The carbon rods could be used for that. Don"t conventional flashlight batteries have small dia carbon rods in the center?

 

[Janicholson]

Graphite block is best. Far cleaner and less likely to get blended into the metal. Jim

 

[echofarmma]

I work in a shipyard and most of the time copper is not available so the welders always use pieces of 1/4 aluminum plate when they need a non-stick backer. Its also alot cheaper than copper.

 

[teddy52food]

What is graphite block? I do a lot of welding & never heard of it.

 

[Janicholson]

The solid form of graphite, a block (like pencil lead but more pure) is sanded to fit the curve of the repair so as to shape the metal as it hardens. It melts at about 6650*F thus it does not melt when shaping the weld opening. Jim
Some applications of it.

 

[samn40]

I simply use the face of my copper hammer which is kept in the workshop for hitting those things that don't need dented!
Sam