Butane blow lamp for silver soldering

Discussion in 'Engineers' Talk' started by nitro, Aug 19, 2005.

  1. nitro

    nitro New Member

    Hi all,
    I am having trouble silver soldering brass.
    A brass tube 55mm long, 40mm dia with a 2mm wall thickness has split along the length. I have used a coping saw, and enlarged the split to remove any ragged edges, filled the split with a shim of brass such that there is an approximate gap of 5-8 thou. each side of the filling medium - the intention is to silver solder this joint - the joint has to be strong, as the casing is holding a spring that is 1.8 mtrs. long, 0.5mm thick and 38mm wide ( you do not take chances with that amount of power !!). Now all I have is a butane blow lamp and a
    pencil
    butane torch (850 deg.C). I have tried heating the tube with the blow lamp and at the same time using the pencil torch to supply the main heat with fire bricks all around no use, still not sufficient heat, mass too large. Many years ago at school I remember the bunsen burner, and the air admit valve to increase temperature.
    1. Does anybody know if the standard blow lamp is at the optimum air admit with the holes that are drilled in it and hence max temp. can be achieved.
    2. Would it be worth making my own "bunsen" and would the heat output be any higher by reducing the outlet pipe to say 1/4.inch diameter. Also to possibly inject air under pressure into the gas stream?.
    3. No I do not want to buy propane, or take it to anybody else to do - small matter of pride involved here.
    4. Silver solder with 15%Ag. and 85%Sn. melts at around
    650-680 Deg.C. I think, and I am using a basic borax flux.
    Well that's about it so come on chaps any thoughts,
    Kind Regards, Nitro.
     
  2. jasonb

    jasonb New Member

    I think your problem is the butane, I use a propane torch and it would easily cope with what you want to do. It may also be the regulator on the butane as most of them will only flow a small amount of gas. How hot is the metal getting, you need to get it to a cherry red for the solder to flow. Are you using the right flux and what silversolder are you using as they have different melting points, Easyflow will be your best bet.

    The joint must be absolutly clean otherwise there is no way the solder will take.

    BTW my hobby is model engineering where propane torches are the usual tool for silversoldering copper boilers although the commercial ones are done with the aid of oxy acetalyne.

    Jason
     
  3. nitro

    nitro New Member

    Jason,
    Thanks for the reply. I am using easy-flow and the flux is correct. The job is not getting sufficient heat, as the flux should "run" when the heat is correct, (this keeps the oxidization at minimum) then you should be able to remove the heat and the SS will melt at this temp. I have kept the gap down for capillary action as SS is of no use for filling. Propane - well as an engineer yourself, if there is an easy way or a hard way - where is the challenge - or enjoyment in the easy way !! besides - I don't have a propane torch ( too old and tight to purchase same). It is me just wanting to get maximum out of a commercial design that just might not have been fully thought through. If all else fails then Propane will have to come into play, but in the meantime - never give up!!!
    Kind Regards,
    Roger.
     
  4. jasonb

    jasonb New Member

    Your torch should still be OK for propane, just the regulator needs changing. If all else fails try to pick up an old parafin blowlamp from a boot fair you will enjoy restoring it and they give off plenty of heat.

    The only time I have not been able to get the SS to flow is when I have picked up brazing rod by mistake!!

    Jason
     
  5. nitro

    nitro New Member

    Jason,
    Thrown in the towel and went and bought a propane torch today, it will come in useful for other jobs no doubt, not only that, but I need to get this job finished soon, as a friend has a clock that has just gone bang !!, the trouble is I don't charge for repairs and most of the parts I make. However, I have tried this new torch, and with the dimensions of the tube as original posting, it will still not glow anywhere near red after 5 mins. of applied heat and firebricks around,I think I may have to give in and find somebody with a oxy-propane or stronger. Thanks for your advice, Kind regards, Nitro.
     
  6. jasonb

    jasonb New Member

    What size of butane / propane are you using? is it aerosol type. I use a 4.5kg calor bottle with a bullfinch torch with 22mm burner and the regulator between 1.5 & 2 bar. Its enough to make the brass sagg if I keep the heat on too long.

    Jason
     
  7. nitro

    nitro New Member

    Jason,
    Bottle is 0.4kg. pressure at 25 bar Manufacturer "Bernzomatic" looks like USA origin. Burner is 15mm pencil and what the regulator is set to I do not know, but gives an adjustable flame of 0.5" to 2.5". No specification sheet with unit.
    Kind Regards, Nitro
     
  8. jasonb

    jasonb New Member

    The Benzomatics are a mix of propane & butane, as I said you need a torch have a look at Machine Mart, they do them from about £20.00 with a calor gas bottle from your local petrol station, garden center etc.

    Jason
     
  9. nitro

    nitro New Member

    This is true, but I did pay the extra and bought Propane only, not a mix of butane/propane, the cost was about £18, but such is life, Had a chat with a local clockmaker today, and he said that sometimes 150 year old brass for some reason can be a pig to SS, so it looks as though I may have one of them, just my luck !!!
    Kind Regards, Nitro.
     
  10. gardm1nt

    gardm1nt New Member

    For future reference I have overcome this type of problem by pree heating with a propane detail roofing toch (borowed from a roofig contractor mate) followed up by my normal primus propaneblowlamp.

    Regards Paul
     
  11. nitro

    nitro New Member

    Many thanks Jason & Paul, if all else fails I will try and purchase some brass tube and start again, I have a small lathe, so turning the recess for the end caps should not be too much of a problem - could think of a new hobby !!!!!!!!!!!!!. Kind regards, Nitro.
     
  12. Datacom

    Datacom New Member

    Try MAPP gas, its a mixture of acetylene and propane, burns much hotter than propane alone.
     

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