A good friend has asked about equipping himself with brazing equipment for very fine work, I have given him a few pointers, but apart from Sievert and a couple of others, can the group suggest products that he could look at please? Peter
-- Peter A Forbes Prepair Ltd, Luton, UK email@example.com
I use a Smith 'Little Torch' for fine jewellery work and love it - mine is oxy-propane but the oxy-acetylene version goes even finer. IIRC the ad shows silver soldering two wires inside a rolled cigarette paper without burning the paper - pretty d**n fine! Prob get ir from on eof the bigger jewellery supply houses, HS Walsh or Suttons spring to mind.
Another possibility might be a Brown's gas generator - Brown's gas is mixed H2/O2 produced by electrolysis of water. You can make your own generator for a tenner or two, or buy one for a hundred fifty quid or so, again from jewellers suppliers, although eg a Microflame brand generator can cost over a grand. Typically they use a hypodermic needle as the torch nozzle, so very fine it is. They don't work well for high-power torches.
Very clean hot flame, can even melt small platinum parts, no gas to buy, and only cost pennies to run, but the flame is not suitable for all metals and conditions - for silver soldering or brazing this is not usually a problem though.
Please note that there is a lot of "rubbish" (I am being polite) talked about Brown's gas - but for very small brazing tasks it does work pretty well.
For some thing a little larger, say from 1/4 to 4 oz, for preheating I use four extremely cheap (three were under than a fiver, including an often-used large £4.99 "weed-wacker" torch from Aldi, another was £11) variously sized butane torches, and a "well" made of firebrick lined with bits of ceramic kiln shelf offcut.
For the actual brazing I use a Minox oxy/propane torch with a 4 lpm PSA oxygen generator (ex-medical concentrator, £110 on fleabay).
I have even used oxy/gas, as in domestic gas, but it needs compression for my torch and it is probably a severely un-CORGI thing to do. :)
miniature spot welder called a PUK-II. The 3 torches are: Standard Sievert air/propane, which is used mainly for annealing - the smallest nozzle available produces a flame too big for really fine work. A unit made by MicroFlame that uses bottled oxygen and propane or butane. There are a number of different sized nozzles ranging from the largest of about 5mm diam, down to a tiny one that gives an intensily hot flame about .3mm wide and 2mm long. A water torch: a device for converting water into hydrogen and oxygen and a torch with interchangeable nozzles. The flame sizes available are similar to those of the MicroFlame unit but it is far more usable because there are no bottles of gas to look after and refill, and the gas mixture produced is always right. The gas is passed through a special mixing chamber that contains a volatile liquid that modifies the temperature of the flame, or water if the very high temperature of pure oxy/hydrogen is needed. The chamber can also contain special flux so that no additional flux is required. The PUK-II welder gives results similar to a lazer welder, but uses a short duration arc instead. Tiny 1mm, or less, spot welds can be made in various metals within 1 or 2mm from your fingers. There is very little heat produced.
Yes I was always a tad concerned about that. I picked up a Microflame unit a few years back, and pulled it apart to see how they handled safety. It was just a thick steel body with an electrode insulated from the body protruding inside, a screw on filler cap, and a pressure switch. 12v DC via the switch to the electrode, and when the 'bomb' was sufficiently pressured it stopped producing. The output was piped via an external tank filled with M.E.K. which I assume contributed to the flame characteristics. Nozzle was a hypodermic needle. Safety - what safety !!! Never really used it in anger, and it was disposed of when 'I didn't move house'
I guess the safety comes from the small diameter of the nozzle - the flame can't propagate back into the chamber because the nozzle will conduct the heat away rapidly enough to keep the gas below ignition point.. A bit like the miner's safety lamp, where the flame can't propagate through the fine metal gauze.
It isn't actually as dangerous as you might think - the gas is under low pressure, and if the gas in the steel reservoir blows it just goes "tink", there is very little excitement. The amount of gas is small, and while there may be some noticeable shock waves there is very little blast produced as the gas cools very rapidly.
If you are making your own, I have seen 14 g steel recommended for a litre or two of gas, 12 g for up to a gallon or so. And use redundant overpressure safety blowout devices, you really do not want high pressure H2/O2 mix anywhere nearby.
I think even a PET bottle would be okay, must try it sometime (from a distance!!). Most thicker plastic containers too. But don't use glass or anything that might shatter.
Afaict MEK, acetone or alcohol are used to make the flame reducing and add a little CO to the flame gas, which can be useful to prevent oxidation of the metal - some metals can even rob oxygen from the water in the flame. It also brings down the flame temperature, a H2/O2 flame can be too hot for some jobs.
lemel_man mentioned the use of flux in the bubbler, but I have not come across that - anyone know what it is?
Yes, thanks, we have a standard search set up on ebay and have a trawl regularly. best hunting grounds are the 'States, as the Bullfinch pattern was sold only there for many years, so you find quite nice collections coming up.
We have brought back many nice items on our trips :-)) The beauty of having so many internet friends, plus Tim & Sally who we go and visit, is that we can buy stuff and ship to them and they hold it until our next trip.
Also, it can be very cost-effective buying things like Amphenol connectors over there and getting them posted to home rather than the factory. VAT, Duty and Handling nearly always get charged on stuff addressed to the company, while rarely do we see it on private packets/boxes delivered to home.
-- Peter & Rita Forbes Email: firstname.lastname@example.org Web: