talk to me about brazing...

[BrokenBiker]

right, i have a limited knowledge of brazing/silver soldering...

i did a bit of it as an apprentice on small parts, usually things like a steel part that had been snapped and for what ever reason it wasnt allowed to be welded, usually becasue it was either hard or cast iron, so it was brazed/silver soldered.

the technique used was to drown the area to be joined in flux, get it good and hot with the oxy acetylene then take the flame away, dab rod in until you can see the braze/solder flow into the joint becasue of the capillary action...

i thought this was the only way brazing with a flmae was done, and then tig brazing was just like tig welding but without melting the parent material...

anyway, watching a video by Abom79 Here and the way he is brazing just looks like oxy welding to me...

can anyone explain how this differs from the method i described above. more of a curiosity than anything i am looking to do but once i have a decent sized workshop/garage i may be interested in brazing

 

[dan.taylor.1]

I think the rods he uses have a lot to do with it looking different to how you described brazing.

 

[BrokenBiker]

I think the rods he uses have a lot to do with it looking different to how you described brazing.

do you mean the coating on them? think that is the flux already on the rod

 

[WorkshopChris]

To me coating with flux, heating then adding the rod sounds more like soft soldering. When brazing with oxy acet it is more normal to heat the work then heat the rod and dip into the flux. ( you can also get flux coated or impregnated rods) Then apply the flame to rod and the work as you would in gas welding. Obviously without melting the base metal just heating it.
Have a look on You Tube at Keith Fenner for some good brazing videos.

 

[brightspark]

the rods hese using are flux coated -u can buy a tin of flux and dip--the un coated rod in when its hot. the principle is just the same as gas welding and u feed the rod in to the molten puddle and build it up as u go along. to be honest the guy in video would have been better keeping the propane torch on the job and the brazing would have been far- -easier and neater than just the acetylene torch

 

[Tigman]

what you used to do is silver soldering soak part with flux and heat till cherry red then dab on silver solder and it flows in !
what matey is doing is oxy/acetylene brazing with flux coated brazing rods !

there is a difference

 

[Bill Edwards]

I'm not watching the video (not at 25 ish minutes) but brazing with either fluxed or unfluxed (dipped in manually) requires the parts to be heated, basically 'til they're just starting to glow dull. Then the braze rod is placed in the flame which is required to make it melt, it needs the heat from the torch.
Of course, some skill is required to direct the correct amount of heat into the work piece and also the rod at the same time.

I'm not a soldering man, but certainly electrical/plumbing (if not all) kinds require the work piece to be heated then to use that heat to melt the solder, it's a very different process.

 

[BrokenBiker]

so basically when i was told i was learning how to braze, i was actually learning how to silver solder? pretty much sums up the quality of the rest of the apprenticeship really, supposed to be a leccie and spent more time in tool room than on electrics, if it wasnt for the fact that the majority of the written work could be done at home i doubt i would have passed based on the work and tuition provided

 

[Mr shiney]

There is a bit more to it and the answer is it depends on what you are doing.

If I am brazing a tube frame for example, I will paint flux round the joint then heat the part all round then heat the rod and get it to flown in to the tightly fitted joint. It will flow round just like plumbers solder does on copper pipes. This leaves a thin line of braze around the joint and it travels through on capillary action.

If I am joining parts that don't have a great fit then I will put it in just like TIG and build it up so it looks like a bronze weld. Still using a flux so it flows.

With really well fitted parts it's a real joy to watch it flow round and leave little mess to clean.

 

[BrokenBiker]

There is a bit more to it and the answer is it depends on what you are doing.

If I am brazing a tube frame for example, I will paint flux round the joint then heat the part all round then heat the rod and get it to flown in to the tightly fitted joint. It will flow round just like plumbers solder does on copper pipes. This leaves a thin line of braze around the joint and it travels through on capillary action.

If I am joining parts that don't have a great fit then I will put it in just like TIG and build it up so it looks like a bronze weld. Still using a flux so it flows.

With really well fitted parts it's a real joy to watch it flow round and leave little mess to clean.

this is exactly what i was doing whilst being taught...usually the parts that were broken were sleeved over the break and then brazed, covered in flux, heat it all up and watch the rod flow into it all

 

[brightspark]

its a bit different though building up a cracked iron casting that has been-v out and filled

 

[BrokenBiker]

its a bit different though building up a cracked iron casting that has been-v out and filled

thats why i started this thread as after watching him brazing i thought he was actually bronze welding at first

 

[the snooper]

its a bit different though building up a cracked iron casting that has been-v out and filled

dont worry the mondeo engine is sorted

 

[BrokenBiker]

dont worry the mondeo engine is sorted

haha i was actually asked if i could just weld a plate over the hole...

 

[Mr shiney]

its a bit different though building up a cracked iron casting that has been-v out and filled

Yep, that's the second method I refer to where I build the material up.

 

[BrokenBiker]

i assume it has to be done with oxy/acet or oxy/propane, normal propane wont work?

 

[Turbo]

BB - you have started the exact post I was thinking about!

A lot of my questions have been answered so far but I've something to ask. What is a good general purpose brazing rod & flux for joining mild steel & cast iron?

 

[Mr shiney]

To be honest I have never tried, I only use oxy acetylene for my gas work.

i assume it has to be done with oxy/acet or oxy/propane, normal propane wont work?

 

[HughF]

If it's relying on capillary action, it's silver soldering. The bike folks call it lug brazing, but I'm pretty sure they use easyflo rather than sifbronze...

Oxy propane is fine for both, it's a complete waste of acetylene to use it for silver soldering or brazing.

 

[BrokenBiker]

i assume you could just use a propane torch with a big nozzle to do silver soldering if its only relying on the part being hot enough to melt the solder?