need advice on tublular welding

I wouldn't put any more brass on it because it will all have to come off to weld. My first thought would be to get some pipe where the inside diameter fits the outside diameter of the frame and make a patch. The frame may not be mild steel but that won't be an issue if your patch is thicker than the parent material.

A small MIG welder using the on-off technique...once the hole is filled, grind the top stuff down to almost flush, LET IT COOL, then lay a nice bead (or a couple of stringers), to tie the base metals together. If desired weld a small patch over the area for extra insurance and peace of mind.

Doobie

Zorro wrote: I wouldn't put any more brass on it because it will all have to come off to weld. (clip) ^^^^^^^^^^^ "I wouldn't put any more brass on it because IT WILL ALL HAVE TO COME OFF TO WELD!" I am repeating that because it is critically important. The alloy of steel with brass is brittle. You must not wind up with brittle areas in your repair. This is on the bottom of a motorcycle frame, and your life may depend on it.

BTW, I am glad you did not succeed in closing those holes with braze rod. The repair would have been cosmetic only.

Thanks for the advice. I think I'm going to hire a professional, but I have a couple of questions. First, what is the on-off technique using a MIG. Second, if brazing is so bad, why is it so hard to grind it off. Is it simply that it does not adhere to the base metal or is it something else.

thanks

Well applied bronze brazing is in the 40kpsi to 50kpsi range, not too shabby! But it is still less then the 60kpsi for 6xxx series rod or 6S series wire and the 70kpsi for the better stuff.

That said, I always used brazing on thin material that has fatigue cracked. The brazing flows over the cracks and the hardened zone next to the crack. For new work, its always weld.

Do>>A small MIG welder using the on-off technique...once the hole is filled,

stonecreek wrote: (clip) First, what is the on-off technique using a MIG.

The on-off technique is this: set the heat so that you get quick, full fusion, and then keep interrupting the weld power, so it cools, and does not melt a big hole.

The problem with grinding away the braze metal is that, if the brazing was properly done, on a clean surface, with flux, the brass "wetted" the steel, and it is present right to the bottom of each grinder mark, groove or notch. You have to get rid of all of it, which means grinding away good metal (steel), to get rid of the bad (brass.) On your motorcycle frame, you are going to wind up with thinner walls than you would like. The suggestion to weld a patch over the rewelded area may correct for that.

It is a manual form of pulsing.

The brass will contaminate any proper welded repair which is attempted later. So every bit of it has to be ground out before you can proceed to weld. It is hard to grind out because it "wets" to the base material, and you have to grind down below the deepest previous grinding mark to get all of it.

Brazing can be very strong if the joint is an overlap joint with a very narrow gap (about 0.005 inch gap max). For example, one pipe slip fit into another, as with plumbing fittings or the lugged joints on a bicycle rame. With proper joint design, the strength can be up to around 150,000 PSI.

But bridging a larger gap will result is a progressively weaker joint. By the time the gap to be bridged gets up to about 0.020, the joint will only be about 12,000 PSI. So brazing is not suitable for filling a hole in a structural part.

Gary