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I was told that brass it the thing to use a welding backer. does anyone know if copper would also work as I have access to some fairly thick pieces and will try to beg them off the guy that has them so I can practice welding this weekend

Jason,

I have alwaqys been told that Copper was the best backer material for welding.

Copper or aluminum is what you should use, do not use brass it will contaminate your weld.

but I thought the bren welding jigs are made from brass?

TOM R wrote:but I thought the bren welding jigs are made from brass?

No they are aluminum, and some guys have made them from copper.

okey dokey

Ok...I'm extrememly interested in how your backer works. Does it bolt to the holes in the reciever to keep it still? Or is the whole thing clamped to a jig of some sorts? Man I wish there was a tutorial picture of the various steps you guys a taking on this task.

Skip in Va

I'll try to explain my understaning of it. maybe others will chime in with more info.
When the recievers are cut up, they use a torch that blows away a little material that needs to be replaced when you weld it back together. you need to place the backing metal inside the reciever under the area to be welded and shim it so it is tight against the area you are working on. that way when you weld there is much less material you will have to grind down inside because the backer held the welding flush on the inside. If you would use steel it would just weld it to the reciever, but the welding will not stick to copper. I did a trial run and it work ok but the backer I used needs to be much thicker than the scrap I used.
another guy told me that thicker material will also act as a heat sink to help prevent warping.

sounds rite to me jason

Roger that Jason!

Description well worded, and understood.

Thanks....

Skip in Va

this afternoon I was at an abandoned farmplace that I trap and came accross some heavy pieces of cast-iron. I tried using it as a backer with some scrap, and got the best results so far.

has anyone else used cast? the price is right when you find it laying around.

that is a great/cheap (especialy since I have some)idea anyone see a prob with using cast as a backer

Guys I will post some pictures of the "jig", now keep in mind that this is only for the I.O. rec. that are chopped in the rails. The 3 cuts don’t need this.

I would be cautious when using the cast backer as it may weld itself fast if you are tig welding these like they should be. That’s why aluminum or copper is used, but either way makes sure that you heat the area that you are welding first with a propane or map torch. Or after you have made all your tacks they will get small cracks cause the backer will act as a heat sink and draw the heat.