Welding question

[Bob_Koch]

I'm watching the progress that bud's truck is making on chopping his cab. Looks great by the way. I see the sections have a small gap between them for the weld. When I was learning welding, I was taught that the metal pieces should make a tight fit. No gap between them before welding. Now I'm seeing the clamps that actually give some space. I've seen these for sale from Eastwood and at Harbor Freight. Someone enlighten me here. When do I want that small gap between my pieces to be welded and when don't I.

Thanks guys, I always appreciate the great info here.

[buds truck]

I'm watching the progress that bud's truck is making on chopping his cab. Looks great by the way. I see the sections have a small gap between them for the weld. When I was learning welding, I was taught that the metal pieces should make a tight fit. No gap between them before welding. Now I'm seeing the clamps that actually give some space. I've seen these for sale from Eastwood and at Harbor Freight. Someone enlighten me here. When do I want that small gap between my pieces to be welded and when don't I.

Thanks guys, I always appreciate the great info here.

word I get is when you butt weld without a small space betweed the metal, it can make the metal expand and oil can the work. I have welded for years and have done it both ways. The gaps in my roof are there solely to make room for the clamps. By the way, Bob, I got my clamps on e bay for a lot less than eastwood, could not find them at harbor freight. Bud

[Tony WestOZ]

Generally a gap is preferred. As mentioned it helps with reducing warping, and reduces the chances of bad penetration.

Sometimes if I am doing a small patch I will go for no gap, but this is only when using oxy and no (or minimal amounts of) filler wire.

[Plymouthy Adams]

butt welding is great...with this you use no media..just the two pieces of material..I like to do this with pinch weld look..say lower rockers as they join..trim one about 1/8 inch longer and use the torch to melt them together..as for the little clamps..they are the cats meow..I have plenty of them..as for the gap..I like the small gap you need with these...as I weld primary with torch...just don't care for the brittle bead the mig leaves..the torch welds are easy to gind, bend real well and easier to work with hammer/dolly without cracking...matter of preferrance for sure...