brazing, anyone done it?

[Tharg2007]

has anyone any experience of brazing? was thinking at some point in the future i would like to fit some track ends on a frame and decided to look up brazing on tinterweb. From what i gathered the best way is to prepair the surfaces, use flux, use oxy assetiline (if thats how you spell it) and some good brass wire.
I also saw someone braze with a coat hanger. Now my question is, would a regular butane torch be enough to braze? or would using a butane torch and a coat hanger to braze on some track ends lead to a broken neck?

 

[Gerry Attrick]

No, you can't use just a butane torch for brazing 'cos it aint hot enough. Oxy acetylene is the bis but its not (with respect) for amateurs. Neither is brazing for that matter as its not a skill acquired in ten minutes. Speak to a good frame builder who will do the job for much less than it will cost you to replace the ruined frame you will end up with if you DIY.

 

[Gerry Attrick]

Oh I forgot. You can't braze with a coat hanger.

 

[Tharg2007]

Oh I forgot. You can't braze with a coat hanger.

View: http://www.youtube.com/watch?v=_FARfmZINJY&feature=related

 

[Gerry Attrick]

Ah, listen carefully and read the title of the video carefully. He is welding with a coat hangar. Welding is not the same as brazing.

 

[Tharg2007]

No, you can't use just a butane torch for brazing 'cos it aint hot enough. Oxy acetylene is the bis but its not (with respect) for amateurs. Neither is brazing for that matter as its not a skill acquired in ten minutes. Speak to a good frame builder who will do the job for much less than it will cost you to replace the ruined frame you will end up with if you DIY.

I wasnt thinking of just going for it on a frame, I was going to practice on bits of metal for a good while first, then if i felt confident i would do it on a £20 ebay job. Im fairly competent in these kind of things and am able to pick things up quickly so I reckon if i was to practice a little it would be quite easy to get a good job done.
Seen loads of youtube footage of brazing techniques this should be enough to make a start on some odd bits of steel.
Also check this amateur out, he did a very nice job http://www.bikeforums.net/showthread.php?t=200196

 

[RedBike]

You can just about (and it is only just) braze small parts with a butane torch. However, I don't think you'll get away with it for track ends. You'll never get the ends of the frame hot enough. The heat will just disipate through the frame.

A coat hanger?
Most brazing rods are some sort of brass alloy (although there's loads of types and loads of different materials available.)

The process is simple. You heat the object needing brazeing (the frame) so that when you put the brazing rod in conact with it the rod melts (You don't melt the rod with the torch). The melted rod runs between the two parts joining them together.

 

[Tharg2007]

Ah, listen carefully and read the title of the video carefully. He is welding with a coat hangar. Welding is not the same as brazing.

fair enough

 

[Gerry Attrick]

Yes ok, practice, practice and practice and you will get good........if you don't blow yourself up with acetylene first.

Seriously, you do need to take good advice from someone who is experienced with that sort of kit. I have seen and heard of far too many accidents with oxyacetylene equipment. Not only that, unless you can borrow gear, (and no responsible welder would lend his kit to a greenhorn) it is very expensive to kit yourself out at home. The gauges alone cost over a hundred sheets.

 

[Tharg2007]

i seen some mini kits on ebay, they use disposable canisters, about £100 for the whole kit.
Granted though I dont fancy keeping a bomb in my garage.
Other alternative is a brazing torch for an arc welder, reading that the flame isnt that constant on these though but should do the trick.

 

[Gerry Attrick]

Yes there are disposable canisters available. I've never used them so I can't say if they are up to heating something like a frame tube and lug to a high enough temperature. Often these disposable jobs are actually butane and compressed air which can permit brazing on small items.

Brazing torches on arc welders bring their own problems in that you must view the process through a face mask. The darkness of the visual filter hides the colour of the heated metal to such an extent that is is nigh impossible to know how hot it is getting. Add to that the ferocious heat of the set up and you have a recipe for a melted frame.

Don't forget that as the frame tube walls are considerably thinner than the lug material, proportionally more heat must be applied to the lug than the tube for the two to be at the same temperature.

In addition, I would suggest that a frame builder would charge considerably less than £100 to do the job.

 

[shimano]

yes, those disposable ones will do the job but only in the hands of someone who is already experienced in the art of melting metal. Brazing or welding is not a skill you pick up instantly so unless you're in it for the long term don't - leave it to someone who is and save yourself loads of grief.

 

[Wobbly John]

Most coathangers are galvanised and would give off toxic fumes if you welded with them, so that's not a clever thing to do.

Brazing is fairly easy. You're going to need more heat to unbraze the old dropouts than to fit the new ones, and i hear that the disposable canisters don't last long.

 

[LLB]

Did a bit of braising in school. You need a lot of heat to get it up to braising temp (cherry red IIRC). The blowtorches were fairly large propane or natural gas and compressed air affairs IIRC

 

[mickle]

WJ is right, brazing is easy. I've a £50 B&Q oxy-acetylene kit which I used to lead weld all the flashing on our dormers. It comes with more than enough gas to do a couple of braze-ons and the process is not bright enough to require a tinted mask.