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Old 21st January 2019, 15:14   #11
KWIL
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Silver soldering work on models? Suggest you look at CuPalloys website, www.cupalloys.co.uk

There you will find all the advice and supplies you need, Keith is most helpful and experienced.
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Old 21st January 2019, 19:29   #12
bikerdude666
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Thanks for all the replies. It is proper silver soldering that'll need doing as it is making a working boiler for a live steam engine. I'll practice a lot before I attempt the kit, and the mate who gave me the kit has the stuff to pressure test model boilers, he used to do it for the boat club.

The kit is from an American company called 'Midwest products Co.' I've had a look and they don't seem to do steam kits anymore. It's a nice looking kit, with mahogany strip to clad the boiler, and what look nicely machined parts for the cylinder and flywheel etc.

Thanks for the tips on the equipment. Now you've said about oxy-acetylene I've got a feeling I've seen a couple of smallish tanks on his garage wall that I think he said he used to solder some brass railings. I'll have to have a look and see how much they are, the only blowtorch I've got runs off butane canisters.

I'll try and pop a couple of pictures of the kit up if I get a chance.

Cheers
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Old 22nd January 2019, 10:51   #13
KWIL
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I would be extremely careful about the use of oxy acetylene!

Often far too fierce for silver soldering, high temperature but lower heat than oxy propane.
Many jobs can be done with propane alone, with less chance of melting the brass or copper base metal.

As I said above cupalloys is the expert you should turn to. Web site has much information on techniques etc.
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Old 22nd January 2019, 15:04   #14
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I would be extremely careful about the use of oxy acetylene!

Often far too fierce for silver soldering, high temperature but lower heat than oxy propane.
Many jobs can be done with propane alone, with less chance of melting the brass or copper base metal.

I cannot agree with this. I worked for one of the worlds most renowned manufacturer and supplier of welding consumables. I cannot think of one of our customers that used anything other than oxy acetylene. Our own training centres that were used by the best welders to learn in only used oxy acetylene.

The problems occur because in my experience the operator does not know how to select the correct nozzle and in most cases has no idea how to set up the torch to burn the correct amount of gas. Once they knew what to do problems as you describe go away.

I was taught by the worlds best and I pass this on so you can light a torch up at the correct pressure for any nozzle every time.

Pick the correct size of nozzle, better to be smaller than to large. Make sure the bottle regulators are off and open up both the acetylene and oxygen knobs on the torch one and a half turns. Point the nozzle at your cheek and slowly open the acetylene regulator until you feel a slight breeze on your cheek. Turn the nozzle away from you and ignite the acetylene. If there are sooty tadpoles or smoke coming off the flame the pressure is to low so at the regulator turn it up until it burns cleanly. If there is a gap between the nozzle opening and the flame the pressure is too high, so turn it down. Then slowly open the oxygen regulator until the correct flame is observed. For silver soldering it should be a neutral flame. Adjustments should always be made at the regulator not the knobs on the torch, that's where the control is the greatest. This will prevent getting a flame that is incorrect for the process, too harsh, too dirty etc. When I went out to sort out problems it was always caused by cleanliness, incorrect technique and not having the torch burning correctly. How many times do you see someone just open both the regulators open the torch knob and ignite the flame, then straight away open the oxy knob and set the flame. Guaranteed to be incorrectly set and so not do a good job. Once these issues were sorted the job was done and I was their first call for any further welding issues on MMA TIG MIG Plasm, and powder. Start with the basics get it right and the rest comes.

Temperatures obtained with different gas combos as follows:-

oxy acetylene 3200 deg C

oxy propane 2500 deg C

air propane 1750 deg C but this flame is sooty and not recommended for silver soldering if you want a good joint or it is critical.

My first choice would always be oxy acetylene but oxy propane is ok and widely used on cost, equipment size etc.
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Old 22nd January 2019, 20:16   #15
KWIL
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RobSun.

I am not disagreeing with you, I too have used Oxy A on occasions, but and its a big BUT, we are dealing here with modelling and probably an inexperienced operator.

Hence my advice, take it from the expert in that field, Keith at Cupalloys, he also has an extensive background in the silver solder industry.
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