brazing vs welding?

[dieselnutjob]

years ago I had a colleague you used to braze stuff I think using an arc welding machine with special rods or something, and there is an article here http://www.mig-welding.co.uk/brazing.htm about brazing with a mig welder.

 

He modified a gear stick for me as the five speed box needed a longer throw than the original four speed (504 diesel), and it looked plenty strong enough to me.

 

Whenever I have tried to weld it seems really difficult and of course it's easy to blow holes in things and get heat distortion etc. The advantage of brazing would appear to be the lower temperature and you are only melting one thing (the brazing wire) rather than three all at the same time (two bits of metal and welding wire). Also the 604 seems to be structurally solid but needs repairs to panels, which don't actually need to be welded.

 

Is brazing easier? Any reason not to use it (on non-structural repairs)? what's the best (easiest to use) equipment.

[Guest]

MIG with gas all the way for me.

Brazing makes me think of someone's Uncle Knobhead fixing his Austin Brianblessed in 1967 for some reason.

Don't bother with gasless MIGs, complete toilet.

 

MIG is just practice. Like anything.

[Bren]

Brazing is "cold fusion", it is nowhere near as strong as MIG or MMA, ok for cosmetic pieces on vehicles but I would'nt use it on anything structural.

[cobblers]

MIG welding to a "passable" standard on body panels is honestly not that hard, and the heat is very hot, but localised. Just do loads of tacks 2" apart, then go in the middle of these randomly across the panel, then randomly in the middle of these etc etc until you've got a full join. I bet a lot of the time people blame warping for what was just a badly fitting patch in the first place.

 

I bet you could warp a panel just as badly brazing it (you can warp them with a bloody sander if you try hard enough)

 

I've brazed a lot at college, and I really enjoyed it - I was using gas to heat the metal and feeding a rod in. I'd love to get a chance to do it again, but it's a bit of a dying art. That said, I reckon most of my love for it was because it was a hell of a lot easier than stick welding, which I was also being taught at the time and made a complete bollocks of.

[CreepingJesus]

I was taught all forms of welding many years ago, studying mech eng. The bottom line is this: the reason MiG/TiG is used in automotive work is because a good weld (as opposed to a pretty one) is easier to achieve more of the time. Even a spitty, blobby nasty looking weld, can hold perfectly well. Brazing is easy to learn, but bloody hard to master; chances are you'll end up with a pretty join with all the strength of year old Blu-Tack. I know, I did!

But...and this is a very considerable 'but': brazing done well is fantastically strong, and yet flexible; and has a big advantage in that the lack of heat transfer to the sides of the join, is a distinct plus. The stainless fabrication guys near me use it on some jobs, 'cos the crystallisation caused by electric welding on stainless, can cause the metal beside the weld to fail under pressure.

Honda Racing Corp went to great lengths to make a virtue of the fact that their alloy frames were brazed (at least on the race bikes and homologation specials, road bikes were TiG'd), and took a fair bit of stick for it at the time. But the brazed frames were designed specifically to be brazed, not welded. So castigate brazing for structural use at your own peril: better engineers than any of us have designed 200mph bikes to be built that way!

Personally, I learned to braze with a gas torch and bronze rods (bronze brazing), and I would love to do more. Particularly to build a custom bike frame the old school way, with sleeved joints and so on. I'll need to have a look at the electric technique article, that should be interesting, cheers!

[Barry Cade]

I remember back when I was an apprentice, in the panel shop, and was working on an early E30 BMW. My first go at fitting a quarter panel, and I was pretty chuffed when I replicated the brazed joint under the rear window,inside the boot shut. The foreman then came over and gave me a bollocking as it had to be welded.... even though BMW brazed it originally. The insurance company wouldn't allow brazing as a repair.