Slightly OT, but if anyone is searching the archives at some later date and hits upon bottom bracket shell, I had a nightmare trying to salvage one of these to build a frame. If you have a 3 piece crank, please just buy one from novacycle or one of the other outfits-- they cost $5 for steel without braze on bits. If you haven't got the patience, remember that the drive side is a left handed thread, that means it comes off in the opposite direction from normal. Examine your donor bikes before planning on using their BB shell-- some require weird tools to remove, not a great thing to discover when you finally get a spare evening to work on bikes. Remove EVERYTHING before cutting the shell out of the frame. Cranks can be hammered off, but if they won't come off, just use the acetylene torch to heat the crank arm near the shell, but do not heat the shell or the bolt inside the crank arm. If the arms are aluminum, they will not change color before suddenly bubbling and then melting, so watch for the bubbling and move the torch elsewhere. After heating, they come off really easily, but they are very hot.
You will not be able to gas fusion weld a bottom bracket to a frame without ruining the ball bearings inside. Like I said, they have to come out.
Once the crank arms are off, if the bits that screw into the shell won't come off, use the torch on the shell to get it to expand. Then start using a big wrench or punch and hammer to try to spin those inserts. Don't mutilate the inserts before heating the shell, or you will be in for a world of pain trying to get a tool on them later.
If all else fails, this worked for me. I took my grinder and carefully ground out a notch in the insert. I used an old chisel and the hammer to try to make it spin, but no go. Too much rust inside. So I carefully ground off as much of the insert as I could, then used a Dremel with a cut off wheel (well, 2.5 cut off wheels total...) to remove as much material as possible without ruining the threats on the BB shell. Then I used the chisel again. Apparently I removed enough material to lower the friction enough for the insert to turn inside the shell. I then worked it in and out to restore any thread I had mutilated. A whole lot of work to save $5 though.
