I discovered a great welding technique last week (by that I mean well over a year ago). Whilst browsing another forum I came across a technique using a 2pence piece under a hole to stop the weld blowing through. However, these days with copper being so expensive newer coins have a lot more iron content so it is best to use an older coin (test using a magnet) other wise you could end up welding the coin to your bus! By placing a piece of copper under a hole you can plug weld it up using a MIG welder, The weld will not stick to the copper and the copper acts as a heat sink to reduce distortion. The back of the weld is a lot neater needing less grinding (ideal if the grinder can't get in there)and there is no risk of blowing a hole in thin metal. I've been welding for a few years and this is the first time I've heard of it or used it. I'll be using this when butt welding some bits - especially if I cant get behind the weld to grind down. It is a great techneque I will be using it a lot ;D You can buy a tool called a welders helper or copper spoon but I have made one using an old piece of copper pipe hammered flat at one end. Heres a picture of the one I made Obviously the copper can get hot so to stop you burning your hands you can put a stick in the open end to hold it in place with out getting burned. here it is in use..... I've used this metod quite a few times now and it is especially useful when plugging up small holes in old fragile or thin metal
Great tip, very easy. Im a sheet metal worker /welder by trade and we use this Method. Also you can use aliminium..
As Baybug says, its a great technique if you can access the back side of the welded area, the method I use is called "breaking the arc" small spot welds in quick sucession, but allowing each weld to cool slightly before the next weld is applied, this allows the welded area to be built up, although a reactolite welding screen is necessary for this technique.
thanks guys I've also seen a product from frost tools called cold front. Its a putty that is supposed to keep the surrounding area being welded cool to stop distortion. I've not used it as its a bit pricey but it may be worth a punt on my next project ;D http://www.frost.co.uk/automotive-welding-tools/cold-front-414ml.html
How quick can you pump? I've been using air-line for a while and got to say it works a treat plus no water into the equation has got to be good. I suspect once the putty is warm it stops working so you have to cool the putty - round in circles? Never tried it though.
