Help me to braze

[Stanky]

Can anyone suggest a good brazing kit for occasional use to repair exhausts/lawnmowers and small metal things, as well as a source of heat to undo seized fixings on cars? I had in mind something like this:

 

https://www.thewelderswarehouse.com/Welding-Supplies/Mini-Gas-Welding-Kit.html#SID=340

 

However the reviews of all <£400 kits seem to be a bit lacklustre. Are they genuinely crap, or do people have unrealistic expectations of them?

 

Can anyone recommend me a kit thats suitable for a beginner, for occasional use and under £200 or is this not possible?

 

 

[spike60]

Are you not better off with a better quality one 2nd hand?  I think the hobby ones will eat the little gas bottles. There's a couple of old workshop sets on Ebay, replacement pipes, nozzles etc are readily available and if you use it much at all you will likely end up with full size bottles anyway.

[Stanky]

Happy to entertain the idea of 2nd hand - what should I look for?

[Christine]

carbon arc torch

[spike60]

carbon arc torch

Can you heat things with one? The only arc stuff I've been involved with has been to gouge out with.

[spike60]

Happy to entertain the idea of 2nd hand - what should I look for?

I'd be looking at a well used set from a garage that they demonstrate if you're not sure. They are typically well battered and abused but it doesn't matter as long as still functional.

[Stanky]

Are they not massive though? My thoughts were that the little one would be more portable and easier to get into confined spaces than one with 5' gas tanks which I'll never use up?

 

***edit***

 

This sort of thing?

 

https://www.ebay.co.uk/itm/Bernzomatic-torch-cutting-brazing-welding/253271181934?hash=item3af8238a6e:g:LuwAAOSwH-daFEpb

[Christine]

Carbon arc torch.

 

You'll need an old arc welder.set at  30 - 60 amps not critical really   (DC inverter ones will work but one electrode will get far hotter than the other .  )

 

 The new ones on ebay at 52 quid seem a bit steep for what they are !!  Look round boot fairs for an old S.I.P. one like this ..http://www.ebay.co.uk/itm/Carbon-Arc-Brazing-Torch-heating-without-gas-/202067868781?hash=item2f0c2efc6d%3

 

 

You can fit 6mm or 8mm carbons in them.. You slide one rod into the other and create the arc, then slightly pull them apart to produce a "flame " . It will crackle like frying bacon ..

  Wear an arc mask ! Cover skin too , unless you want skin cancer or instant suntan  !   It is crude , but the heat generated is phenomenal .. A 8 mm nut and bolt will heat to yellow in 20 seconds.. A bar of steel up to about  1" x  3/8 thick can be got red hot ,say 1/4" wide red hot across the width, for a nice sharp bend ? Or straightening a bend already in it ?

Drawbacks..you can't get into tight spaces like an oxy acetylene , but you can snap off the carbons to make the thing a bit smaller .. 

I use mine regularly .. For brazing you'd need flux coated rods ..and they're dear !!

 

 

If you have the budget though I'd buy a Portapack and Hobbyweld bottles. Those Benzo won't last 5 minutes

[Stanky]

  Wear an arc mask ! Cover skin too , unless you want skin cancer or instant suntan  !

 

This was what attracted me to a brazing kit  - you seem to need much less in the way of PPE, or have I misunderstood?

[Christine]

Have a look at Hobbyweld oxy acetylene bottles prices.... 

 

I may have a Boc saphire torch ,hoses ,flashback arrestors , an oxy gauge etc , (but no acetylene gauge,  as i use it on me propane bottle !!)   for buttons and postage..Good enough for brazing the odd bit..

Shock... horror... HSE visit    

[Stanky]

Ah, sounds promising - so I'd just need an acetylene bottle and a gauge?

[Christine]

This was what attracted me to a brazing kit  - you seem to need much less in the way of PPE, or have I misunderstood?

Well I've used them  (   several as they're a bit shit ! ) for 40 years  in a shirt  no gloves etc  , when i needed heat NOW !!!  No time to drag huge  bottles out ," I want it red hot NOW ! "   No more dangerous than a MIG .

 

It's oxy acetylene that scares the living  shit out of me.  Suppose there was a fire?  I have 2 x 2 million quid houses next to me.. Say they get evacuated as there's a potential explosion going down?They'll want to stay at the Hilton hotel...At my expense? That's why i got rid of my bottles   As i said,  I still have the torch and  stuff..

[Christine]

I was at Tunbridge Wells industrial site , shopping in Comet one evening some years ago ,with my wife, when a nearby scrapyard (Stan Carpenters?) went up in flames . We could see where the fire was ,1/4 mile away , it was fucking massive.. Then there were explosions.. and seconds later a bottle hit the roof .. I knew exactly what was happening,  and we got the hell out of the site fast .. At the time , i was learning guitar at the fire station with a guy on the night shift . Going down a few days later , It was the hot topic ! They showed me a acetylene bottle..8mm  thick,  split right open and folded back as if one of those old can openers cut a jagged split ,lengthwise! I asked how the fuck do you fight that type of fire safely ?  "You don't... you keep your helmet on and head down, hide  behind something substantial and let the fucker burn itself out "   

 

https://www.youtube.com/watch?v=iam27Mh1zu4

[Asimo]

Carbon arc is obviously dangerous like any flame because it is HOT, but the PPE requirement is due to the flame being such a bright light and much of that light is ultra violet, of a dangerously short wavelength that you do not want to expose your skin to. You get UV burns REALLY quickly on the thin skin on your wrists for example, where a few minutes exposure is plenty for massive blisters.

 

But carbon arc brazing works fine for brazed bodges like lawnmower grass boxes, non-mot car repairs etc.

 

An additional benefit is that the carbon flame seems to burn off rust (I guess the carbon steals the oxygen from the iron oxide) so you can braze succesfully even where the steel is a bit frilly.

[Stanky]

Maybe I will go back to looking at little tanks then

 

Might get away with just blowing up my garage rather than levelling the entire street

[Dead_E23]

a nearby scrapyard (Stan Carpenters?)

I remember going to that yard with my brother to get bits for his Viva - didn't know it had caught fire though!

 

Stan's son in law used to cut my hair at the barbers shop in Chapel Place and would tell me about interesting cars they'd taken in. I was about 10, so not in any position to zoom over and buy them but all ears nonetheless.

[Christine]

Full circle,ironic really , Stan used to supply the fire station with free cars to practice cutting roofs off , then take away the mess !

[Stanky]

Right, back from the dead - I need help.

I had another go with my brazing kit last night and failed again. Please can someone help me to identify what I am doing wrong?

I have 2 bits of mild steel rod, square profile, about 10mm x 10mm. rough milled. Not rusty, but I did not degrease it (possible problem #1). I placed the longer section of bar - about 300mm - in the vice and laid the short section of bar - about 70mm - on top. I turned the taps on on my gas bottles. 1x MAPP gas and 1x Oxygen. I opened the tap on the torch for the MAPP gas and lit it with the striker to product a yellow flame about 8" long. I slowly and carefully opened the tap for the oxygen on the torch until the flame was bright blue and about 5" long.

I heated the two bits of bar with the flame for about 15 minutes until they glowed red under the flame, removing the flame from the joint made them cool enough to go grey again almost instantly (possible problem #2). I applied a pre-fluxed 3.2mm brass brazing rod to the joint which did not melt based on the heat of the steel rod, re-applying the flame to the joint melted the metal in the brazing rod and burned with a green flame - presumably from the flux.

The heat allowed me to twist the brazing rod and break it off from the melted bit, the melted brazing rod remained in the flame of the torch for several seconds before I moved round to the other side and repeated the above for the other side of the joint to make a sort of cruciform shape. 

I left the whole lot to cool overnight and went out to it this morning. The small bit of steel bar lifted off the long bit - the brazing metal hadn't 'flowed' into the joint at all, just sat in the V of the two bits of steel bar one on top of the other. One of the bit of melted brazing rod just fell off, the other has adhered pretty well to the smaller bit of steel bar, but not flowed into the joint whatsoever or adhered to the longer bit of steel bar.

What am I doing wrong? Thoughts include:

- Not cleaned the steel bar properly. Try cleaning with a can of brake cleaner, then grinding back to bright metal with a file or wire brush.

- Not got the joint hot enough, heat it with the torch for longer so it glows bright red. Also headed the brazing rod directly, which should only be melted by the heat of the joint with brazing torch removed

- Not used additional flux paste (in addition to the flux on the outer of the brass brazing rod) 

Anything else? or am I just a ham fisted moron?

[xtriple]

Not hot enough by a long way sadly.

[Stanky]

Full of enthusiasm I strode out last night to try again, cleaned the bar with brake cleaner, filed down to bright metal, fired up the brazing torch to get it all nice and hot and..... Ran out of oxygen.

Bumhats.

I'm currently torn between buying another Castolin 1l bottle for £24.99, or going whole hog* and getting an 8l Hobbyweld bottle for £130. Can anyone suggest anything else? Also, are the big bottles a different fitting? The regulator I have is fine, but I think its 1/8" BSP // M10x1 thread - its from a set designed for the disposable 1l bottles.

[Mr Pastry]

Proper equipment with big bottles will always be better, cheaper in the long run, and easier to use than DIY kits, but there are serious safety issues, as has already been said.   I don't know offhand about the regulator you have, but be very careful with oxygen and always use the correct equipment - don't improvise anything.  I would expect that a Hobbyweld cylinder is filled at a higher pressure than your small one, so would be more economical but  may need a different regulator.

It depends a bit what you want to do.  You can reach brazing temperatures with a straight propane torch, no need for oxygen, but the heat will be diffused over a large area.  Sometimes that is what you want.  Oxy-propane or oxy-acetylene will give a hotter but much more concentrated flame for localised heating.

10mm bar takes a bit of heating, and it sounds as though you are at the limits of what your equipment will do.  IMO it's better to practice with thinner material, and until you learn to control the heating, plain brazing rods and a pot of flux are more useful and more forgiving than flux coated rods.

[Dave_Q]

10x10 sounds quite big and I can imagine you would struggle to get enough heat in as the bars are like big heat soaks.

I would have thought most people would MIG something that big.

I guess you wanted brazing because it's generally thin metal you want to use it on, have a go with some sheet steel and maybe try brazing some m3 or m4 HTS bolts to it?