Learning to braze

Discussion in 'Boilers' started by MRA, Mar 14, 2018.

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  1. Mar 14, 2018 #1

    MRA

    MRA

    MRA

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    Hi folks

    I'd like to make some progress on a 3 1/2" gauge 0-6-0 someone gave me a good while ago - it's what brought me here. I built a furnace and taught myself to cast bronze; I made a 'milling machine'; next missing skill is brazing. I have a little silver solder, but it's so expensive - instead I'm hoping to make a small solid-fuel copper test boiler using brazing rod and oxy-propane gas gear which someone has lent me, but with which as yet I have no experience.

    I have a couple of classic books on boiler making, but all based on older loco designs using silver solder. If anyone has suggestions for things I should read (initially and especially around not blowing myself up with the boiler or the gas gear, but in general about brazing too) I'd welcome it.

    Thanks
    Mark
     
  2. Mar 14, 2018 #2

    bazmak

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    Brazing is one of the easiest and cheapest of the welding processes that can do dissimilar metals. Cleanliness is not as important as say silver solder and you only need to go to red heat rather than full melt.Ideal for steel and cast iron
    Good for building up or filling worn sufaces on larger items.Correct rods and fluxed,usually in combination but you need quick high temp.Oxy/acet is a must
    What more can i say go play
     
  3. Mar 15, 2018 #3

    joco-nz

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    bazmak - Mark notes he's been lent an oxy/propane setup. I would have thought that would deliver enough heat fast enough for brazing?

    Mark - I would suggest you use and abuse YouTube. You can usually find some people who actually have some clues posting some good info.

    Cheers,
    James.
     
  4. Mar 15, 2018 #4

    MRA

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    Thanks Bazmak, and thanks James

    Yes, I've gone a-googling and Youtube has been helpful. It's a funny one this, trying to strike a balance between not being scared of it, vs overlooking something basic / doing something ridiculous, just for want of experience.

    Well, I have flashback arrestors on (anyone know anything about difference between old 'fat' ones with a lever poking out, vs new slimline ones?) and, in lieu of experience and sound judgement, I have ordered some new hoses. I have a whole bunch of acetylene brazing tips on two sizes of torch which can apparently be persuaded to work with propane, and a cutting torch too which apparently will need a specific propane tip, which I'll keep aside for now.

    (I commented somewhere else here recently that cutting disks on a 4 1/2" grinder are quite enough for me. But who knows when I might be called to Barry Island and asked to cut up a steam loco? :) ).

    Quite a lot of this gear has become available since work decided not to host acetylene bottles anymore - new storage regs or something. It's quite exciting, and opens up new possibilities. I'll let you know what happens when the hoses arrive!
     
  5. Mar 15, 2018 #5

    abby

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    Brazing is a simple task BUT be careful when brazing copper , especially if using oxy-acetylene.
    Braze will not flow like silver solder until at a temperature very near the melting point of copper so it is very easy to melt the job.
    Dan.
     
  6. Mar 15, 2018 #6

    joco-nz

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    I’ve done a little TIG brazing and the best thing I did was just cut some metal up and practice, practhce, practice. It feels like you are wasting gas, rod, metal BUT in the scheme of things and to avoid scrapping a part with many hours work in it I think it’s the only sensible path to follow.

    I would think the same practice until perfect rule will apply with gas based brazing.

    Cheers,
    J.
     
  7. Mar 16, 2018 #7

    bazmak

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    as a time served welder/sheetmetal worker.I was sent to Newcastle for 2 weeks
    for welding experience.They gave me a welding table and a box of scrap from 20g sheet to 12mm plate offcuts and said make a sculpture.I just built up a
    structure from bits of scrap all positional welding from thin to thick.Vertical to horizontal and top side and underside,uphill and downhill.After a fortnight i was pretty good.Dont know what they did with all the sculptures
     
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  8. Mar 16, 2018 #8

    MRA

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    It's a little off-topic, but perhaps the mods will allow it as a model engineering forum is unlikely to be swamped by students of art. These people make sculptures around here, and I quite fancy a go at something like:

    http://mahoneysculpture.com/Heron
     
  9. Mar 16, 2018 #9

    goldstar31

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    Oddly I HAD two garden things from Aldi that were decorated with Mig wire strings. Gone now- had to sell my home in Menorca.

    It sort of reminded me that I had once brazed with an old arc welder with a carbon arc thing to melt the borax filled shelter rods. Stuck a rear valance on my old Mini Cooper with it-- so there?

    The other oddity was replacing the steel wire in the Mig with bronze wire.

    Bit tricky perhaps but-- interesting:hDe:

    Might help?

    Cheers

    N
     
  10. Mar 17, 2018 #10

    MRA

    MRA

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    Yes, thanks N. - there's some interesting stuff about MIG brazing here (below), along with quite a lot else about welding - but not gas. Still, interesting to link to it here for reference.

    http://www.mig-welding.co.uk/brazing.htm
     
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  11. Mar 17, 2018 #11

    goldstar31

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    I thought that 'flinging in something different' might stir up a bit of interest.

    Actually, this was all 30-40 years ago - upon retirement from bean counting and the need to earn pennies. I did a City and Guilds in Motor Vehicle Restoration at then Gateshead Tech.

    Coming from a family who were all involved in engineering- at least from the commencement of steam and probably before that, I was always fascinated but obviously forbidden as engineering was a VERY dangerous and poorly paid pursuit. I was 'shanghai-d' in National Service in that direction. And that WAS bloody dangerous.

    So in my dotage, I'm merely playing with what I wanted to do but couldn't then.

    Of course, it is far, FAR easier than 'counting beans' though I still do it for charitable purposes.

    I've hung one of my dinner suits from last night, got a morning suit out ready for Monday and somehow will try to find a bit of 'displacement therapy ' -in between.

    In second childhood--- and mere oblivion

    Norman
     
  12. Mar 17, 2018 #12

    MRA

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    It's amazing, the number of bean counters I know. In fact I am married to one. The way industry has gone here, it's amazing there are any beans to be counted, really - maybe they're counting the counters - kind of 'meta-beans'.
     
  13. Mar 20, 2018 #13

    MRA

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    On this subject - I've been looking on-line at silver solder too. 55% silver in 1.5mm dia rods seems to be something offered by a local model shop - does this sound like something to have a go with for general purposes?
     
  14. Mar 20, 2018 #14

    goldstar31

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    Silver solder is sort of traditional and whilst expensive, is the joining medium between lead soldering and brazing. As you know, a fair amount of heat is required to melt the braze which might be difficult in a small home workshop.

    An important point is flux. Once upon a time, borax was generally available but isn't anymore.
    I wanted a new supply and went into the chemists and they looked at me as if I had come from Outer Space or Mongolia.. I solved the problem by buying from the local welding stockists and bought the variety that would work well on stainless steel too.

    Of course, borax is an excellent killer of ants but I didn't tell you that.

    I hope that it helps you-- and not the ants

    Norm
     
  15. Mar 21, 2018 #15

    mcostello

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    Borax is available in grocery stores over here as Boraxo - laundry detergent.
     
  16. Mar 21, 2018 #16

    goldstar31

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    I recall your similar reply in--2011. Again, I recall Boraxo being in wash rooms as a
    powder in the days when Pontius was a pilate but did you actually braze with the stuff?

    Regards


    N
     
  17. Mar 21, 2018 #17

    goldstar31

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    I might as well be creative and have washed my formal and evening wear shirts and for a repeat performance, I put a wetted amount of laundry powder on a bit of scrap brass plate and cooked it on the top of my gas oven.

    The characteristic clearing of borax never happened but I finally got a charred mess which lit with the characteristic flame of sodium which suggests that there is a clear evidence of --- clears throat- common salt.

    Common salt certainly was the cheap
    but successful adulteration of detergents. Well, it was -- way back in the 1950's when we were playing about with such things.

    N
     
  18. Mar 22, 2018 #18

    mcostello

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    As an aside I bought some borax to use as a scale preventer while heat treating some steel. It protected the steel beautifully. Removal is on par with trying to remove baked on glass. :mad: Several hours in a citric acid bath evidently was a spa treatment for the stuff as nothing happened. A Dremel and wire wheel finally got it off.
     
  19. Mar 22, 2018 #19

    goldstar31

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    Apologies but I was subject to an attempt to hack me.

    So I reply to the removal of glassy borax, everyone in boiler making etc uses a pickle bath. Removing baked on borax CAN be removed with nothing more than a deft finger nail. My dear departed wife simply removed excess borax from children's orthodontic braces was removed that way.

    The accepted removal in the workshop was and presumably always will be done by dropping the work HOT into a dilute concentration of sulphuric acid such as battery acid. Clearly, there has to be an element of shock involved.
    Failing a supply of H2SO4, I always used acetic acid aka spirit vinegar and the somewhat delightful residue from English pickled eggs and such culinary delights will work.

    And I'm NOT joking

    N
     
    Last edited: Mar 22, 2018
  20. Apr 13, 2018 #20

    Wizard69

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    This is so important with respect to any welding process!!! Practice is mandatory and for a home gamer needs to be done regularly even if there is "no need". If waste is a problem come up with welding projects to turn into practice.

    Since I'm not a professional and most here aren't the other thing to engage in is welding warm up just before starting on the real project. You want to get the mind and muscles working in sync before attacking a work piece with dozens of hours in it. This would apply no matter the process, be it silver solder, brazing, oxy welding, stick or flux core. Get your machine and mind dialed in before hitting the real stuff.

     

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