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Silver Soldering Brass

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Chris TickTock15/01/2020 12:30:24
361 forum posts
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Hi,

I have tried in vain (my first attempt at silver soldering) to solver solder a2 pieces of brass together using 2 micro butane torches together and easy flo silver solder No chance I need as one or two people have advised a smith little torch 2 cylinder setup.

So anyone out there got some helpful tips as to gas / suppliers. Acetylene is hotter, will propane / oxygen do. Rental seems too expensive. Have i any viable alternatives?

i live in Cambridge area.

Chris

 

Edited By Chris TickTock on 15/01/2020 12:32:18

JasonB15/01/2020 12:33:08
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You don't need mixed gas just a reasonable size 7Kw+ burner on a propane bottle ONLY will do for anything clock size maybe even smaller.

Did you use any flux? though you probably did not get it hot enough with those small torches.

Edited By JasonB on 15/01/2020 12:33:30

Former Member15/01/2020 13:23:13

[This posting has been removed]

Chris TickTock15/01/2020 13:33:49
361 forum posts
25 photos
Posted by JasonB on 15/01/2020 12:33:08:

You don't need mixed gas just a reasonable size 7Kw+ burner on a propane bottle ONLY will do for anything clock size maybe even smaller.

Did you use any flux? though you probably did not get it hot enough with those small torches.

Edited By JasonB on 15/01/2020 12:33:30

Yes used Borax flux., I think too much heat was dissapating...chasing ones tale.

Jason have you actually silver soldered with a 7KW so can testify to it/

chris

JasonB15/01/2020 13:41:55
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i also use Sievert, the standard burner that they supply is 7.7kw and I do a lot larger items than you are likely to find on a clock, I also have smaller burners for teh same torch but seldom bother to change them.

Unlike some here I would only suggest what I have experience of.

Before

Just after

And after finish machining, the littel bracket to the right is also silver soldered

And another similar size part just after soldering, gets plenty hot enough

Edited By JasonB on 15/01/2020 13:45:12

Former Member15/01/2020 13:43:57

[This posting has been removed]

Martin Kyte15/01/2020 14:03:45
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It's not just the heat you use but the heat you loose too. If you have limited heat do make sure that the work is as surrounded as you can make it, little caves work better than wide open spaces. Butane/air flames will be at around 1600 deg C and propane at around 2000 deg C. (Both far hotter than we need to melt silver solder) For the same gas and torch the rate of heat input will be greater with a larger torch and likewise the heat loss will be less with better insulation. Once heat out = heat in the temperature stops rising. So you can get a bigger torch or you can improve the insulation. The simplest (and cheapest) is to improve the insulation as much as you can.

. . . . if it's still not enough, then you need a bigger torch.

regards Martin

Chris TickTock15/01/2020 14:15:55
361 forum posts
25 photos

Thanks guys and Jason I always respect your advise, just asking.. It is the way I am soldering and the lack of understanding that explains my failure.

I was directing the 2 torches at the joint but the heat would dissipate through the rest of the brass and the helping hand. yes a Sievert would with a larger nozzle through out more heat and heat up the object quicker and hopefully do the job.

Like most folk the expense and hassle of the Smiths little torch is a heavy down side for occasional usage but it does the job. I am minded to go the Sievert route but will chew it over and maybe even have a go properly with my little torches which if used in a better way may work. I had over the top expectations thinking 30 secs and the solder would flow but now know heat the whole thing, joint last and expect 10 to 15 mins.

Chris

JasonB15/01/2020 14:26:13
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Posted by Chris TickTock on 15/01/2020 14:15:55:

I had over the top expectations thinking 30 secs and the solder would flow but now know heat the whole thing, joint last and expect 10 to 15 mins.

This approach will give you other problems mainly of exhausting the basic Borax flux you are using. For anything that may need a longer heat and I class that as over 30seconds and also stainless steel you need a flux that will last such as HT5 or Tenacity No5

Read the guide here and watch the two videos from the same company here and here

Former Member15/01/2020 14:31:14

[This posting has been removed]

Clive Brown 115/01/2020 14:32:45
399 forum posts
11 photos

Propane is much to be prefered over butane. Sievert recommend 2 bar minimum gas pressure for their burners to work properly. This can be quite difficult for a butane cylinder to deliver in a cool workshop, especially as the gas evaporation cools the cylinder further. Propane cylinder pressure is much higher and the pressure can be regulated to a suitable figure.

Re Chis using borax for flux. My understanding is that Easyflo fluxes are better to work with as they have a lower melting point, are chemically more aggressive and  more fluid. The time taken to melt borax allows the workpiece to oxidise more.

Clive

Edited By Clive Brown 1 on 15/01/2020 14:53:11

fizzy15/01/2020 14:58:54
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For boilers I have to use oxy/prop as I need the heat, but for all of my smaller items, gas tanks, burners etc I use a Rothenberger Sure Fire and can verify that they are well made and put out good heat, trigger fired so very versitile too. Nigel,

Pendle Steam Boilers.

Bob Stevenson15/01/2020 15:55:37
385 forum posts
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I also use Seivert, I got mine from CuP Alloys who have some very informative videos on their site.

Watching beginning clock repairers in the workshop I notice that they tend to allow their heat to escape when attempting silver soldering for the first time.........CuP Alloys can supply some 'heat blanket' which you put over the piece and then heat thru the side gap...it allows very little heat to excape so ideal soldering temp is arrived at quickly and easily.

Lastly, silver soldering gets much easier the more you practice so sup up some bits of brass and have a play. The costs in gas/solder/time etc will be handsomely repaid.

J Hancock15/01/2020 16:05:05
387 forum posts

Just thought but you may get a better idea of how hot your item is by doing the job 'in the dark'.

ALL of it needs to be at least a dull red , NOT bright red , that is too much, before touching the silver solder to the work,

Practice will soon improve your success rate.

Chris TickTock15/01/2020 16:25:35
361 forum posts
25 photos

Thanks Guys, really helpful especially Jason & Bob's comments on flux and heat loss.

chris

Chris TickTock15/01/2020 17:18:55
361 forum posts
25 photos

Update

I have found this product currently out of stock but would like your opinion on. The real advantage with the Smiths torch is localised and quick heating, the downside the outlay for a hobbyist / occasional user.

So is this a viable solution, it comes with 2 nossels;

www.thewelderswarehouse.com/Welding-Supplies/Mini-Gas_welding-Kit.html

Chris

Michael Gilligan15/01/2020 17:28:54
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Quite honestly, Chris ... I doubt if you need the ‘Smiths Little Torch’ **LINK**

https://www.cooksongold.com/Jewellery-Tools/Smith-Little-Torch-Kit-Oxy-Gas-Fuel-Systems-prcode-999-7802

Any decent propane system should do everything you [currently appear to] need.

MichaelG.

[another Sievert user ... mostly on smaller jobs than illustrated by Jason]

SillyOldDuffer15/01/2020 18:58:34
5596 forum posts
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Posted by Michael Gilligan on 15/01/2020 17:28:54:

Quite honestly, Chris ... I doubt if you need the ‘Smiths Little Torch’ **LINK**

...

I agree, it might even be unsuitable being on the small side. Not cheap, £200 for nozzle and tubes, then sort out your own gas. (Though Cookson do sell a suitable Oxygen Generator for £500.)

Jumping from 'two Micro-butane torches' to a mixed-gas ‘Smiths Little Torch' after one attempt at Silver-soldering may be premature. Much depends on the size of the job : what's appropriate for jewellery certainly won't do a boiler or vice-versa. My experience for what it's worth is with items weighing about 50g. For these building an insulated cave is vital as is a suitably powerful torch. Mine is a small Propane Sievert, only about 1kW, but it comfortably outperforms a DIY-store butane torch. It's not powerful enough for big jobs, and even smallish ones need care. One thing to avoid is spending several minutes getting metal hot enough to melt solder with an underpowered heat source - the flux burns off. For that reason, a big torch makes soldering easier because it can blast heat in quickly.

Acetylene burns with a very hot flame and, with an excess of oxygen, can cut steel. It's likely too hot for other metals, unless welding is the goal. For ordinary heating purposes, the other gases are as effective and much cheaper. Butane isn't ideal for metal working because it burns at a lowish temperature. The Smiths Torch is a precision Tich, I suspect too specialised.

Can you define the scale of work and metals more precisely? From what's been said, I'm thinking a smallish propane torch without Oxygen for soldering and brazing ounce sized items rather than micro-welding or boiler work. But I'm only guessing from what's been said in other posts about clocks and Sherlines etc.

Dave

George Jervis15/01/2020 19:41:41
73 forum posts
42 photos

Just a quick question can a small Jewellers blowtorch be used to silver solder inside a fire box for the stays?

George

Michael Gilligan15/01/2020 20:04:11
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Posted by George Jervis on 15/01/2020 19:41:41:

Just a quick question can a small Jewellers blowtorch be used to silver solder inside a fire box for the stays?

George

.

I will happily bow to the wisdom of others; but my answer would be ‘probably not’

... I suspect that the ‘heat-sink’ would prevent the joint reaching an appropriate temperature.

MichaelG.

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