Silver Soldering Brass

[Bill PhinnParticipant @billphinn90025]

Chris, this is the regulator I usually use with my Little Torch. You can buy a similar/identical regulator elsewhere, e.g. at the Welder's Warehouse, with different branding. A gauged 0-1 bar propane regulator would be preferable to a 0-4 for accuracy's sake, but I don't think such a thing exists. For your purposes, a 0-4 bar oxygen regulator would be infinitely preferable to a 0-10 bar if you go the oxygen cylinder route.

If you opt for propane as your fuel (I would) and a cylinder, not an oxycon, for oxygen you will need appropriate flashback arrestors. No flashback arrestor is needed for the oxygen line if you use an oxycon.

Follow the recommended pressure settings for each tip in the manual. The rosebud tip considerably ups your firepower, and so is a very useful addition you might want to consider.

Edited By Bill Phinn on 19/01/2020 14:49:34

[Chris TickTockParticipant @christicktock]

Posted by Bill Phinn on 19/01/2020 14:48:44:

Chris, this is the regulator I usually use with my Little Torch. You can buy a similar/identical regulator elsewhere, e.g. at the Welder's Warehouse, with different branding. A gauged 0-1 bar propane regulator would be preferable to a 0-4 for accuracy's sake, but I don't think such a thing exists. For your purposes, a 0-4 bar oxygen regulator would be infinitely preferable to a 0-10 bar if you go the oxygen cylinder route.

If you opt for propane as your fuel (I would) and a cylinder, not an oxycon, for oxygen you will need appropriate flashback arrestors. No flashback arrestor is needed for the oxygen line if you use an oxycon.

Follow the recommended pressure settings for each tip in the manual. The rosebud tip considerably ups your firepower, and so is a very useful addition you might want to consider.

Edited By Bill Phinn on 19/01/2020 14:49:34

Really appreciate post Bill.

Chris

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris TickTock on 19/01/2020 13:56:47:

Posted by Michael Gilligan on 18/01/2020 23:00:22:

Posted by Chris TickTock on 18/01/2020 16:01:20:

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I note in the smiths little Torch manual it states 'when using natural gas a minimum of 1 pound pressure is required'. What is meant by 'natural gas'?

Chris

It's the mains gas supplied to a domestic cooker. In my youth, these were supplied with 'Town Gas' aka 'Coal Gas', manufactured in a Gasworks by destructive distillation of coal. It contained Carbon Monoxide and Hydrogen. Natural gas (often associated with oil), comes out of the ground and can be piped more-or-less as it comes. It's mostly Methane. Lots of fun when we switched from Town to Natural Gas because all the burners had to be changed.

The main problem with piped Natural Gas is domestic pressures are low: in a home, perhaps not enough to run a Smiths, but there's a good chance it would. They're just saying 'don't complain if it doesn't work because you happen to have low pressure gas'.

Using a torch there's a subtle difference between heat and temperature. Taking a shower, you want about 20 litres of comfortably warm water delivered over 5 minutes, about the same amount of heat as a kettleful of boiling water. No-one wants boiling water poured on their head, heat yes, burning hot no!

For brazing and soldering heat is wanted rather than high temperatures, and ideally the heat should be cheap. That means not using exotic gases and not using Oxygen, but instead using a big conventional torch that can burn a lot of cheap gas in air quickly. That delivers the energy (heat) needed to raise a lump of metal quickly to brazing temperature, which is only about 450 to 600C. (Soldering is under 450C). It doesn't help to have a small torch burning Propane and Oxygen at 2500C in a tiny intense flame when solder melts at 180C, and the flame fails to warm the surrounding metal!

The Smith's Torch is aimed at a different problem, ie putting a precision flame on to very small work. I'm sure it's excellent. But the Smiths may not get enough gas through it's tiny nozzle to produce the heat needed to braze something the size of your Long Case Bridge. Adding Oxygen will help by increasing the temperature but for brazing rather than welding more heat is wanted, and that higher temperature is unwelcome. Poor joints are likely. At the extreme, a Smith run with expensive Acetylene and Oxygen is more likely to melt Brass than braze it, even acting like a gas axe. With surplus oxygen it will certainly cut steel. Is that what you want? A clockmaker might need a precision torch and a suitable Propane torch, Sievert or similar.

Dave

[Keith HaleParticipant @keithhale68713]

Borax can be used to silver solder silver. We are considering silver soldering brass.The silver solders used when making joints on hallmarked items have higher melting points than those used by the vast majority of model engineers. Hallmarking quality silver solder can be fluxed with borax.

The two main criteria that a flux has to meet are that it is compatible with the parent materials and the melting point of the filler metal.

Borax does not meet those of the filler. The silver solder and joint has to be needlessly overheated in order for the flux to become effective.

Let me modify my earlier comment – unless you are making sterling silver jewelry that is to be hallmarked – throw the borax in the bin unless the filler metal is brass.!

Keith

[Tim StevensParticipant @timstevens64731]

Borax can also be used when gold soldering. And it is useful stuff whenever you need to make a casting of brass (or silver, or gold …) And it does not go off if kept in a dry tin.

Cheers, Tim

[Keith HaleParticipant @keithhale68713]

Borax is a great material but if the working temperature of your filler metal or casting alloy is above approx 750 Deg, it will not provide the required level of oxide removal.

OK – don't throw it in the bin – it could prove to be a good pan scourer – but it's no good for using with a low or medium melting point silver solder!

Keith

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Tim Stevens on 20/01/2020 17:52:18:

Borax […] does not go off if kept in a dry tin.

Cheers, Tim

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Mine was purchased in the traditional form of a cone … just abrade what you need in a rough ceramic dish.

MichaelG

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris TickTock on 18/01/2020 16:01:20:

Posted by JasonB on 18/01/2020 15:39:00:

…

… Also apparently if you connect a propane cylinder all you need is a camping type regulator don't understand how pressure is maintained, is that a property of the cylinder being compressed if so surely it diminishes at some point?…

All the fuel gases (apart from Acetylene) are compressed to liquid form inside the container. A certain pressure is needed achieve this, between 500 and 800psi depending on the gas. When the container is opened, the gas boils by absorbing heat, and the characteristic high pressure is maintained until most of the liquid has evaporated.

A regulator works by counter-balancing the internal pressure against a diaphragm with a spring; when the pressure on the customer side drops below a certain level, a valve opens briefly allowing a puff of gas to expand into a receiver, before closing the valve again. The receiver is kept full of gas at customer pressure and recharged as necessary from the high-pressure side. Provided the right regulator is fitted to suit the gas and pressures, it's a trouble free system : connect it up and it 'just works'

Acetylene is very unstable, with a number of ways of exploding. It's illegal to liquefy it, instead the gas is forced to dissolve in Acetone or other absorbant, and bubbles out when the pressure is released. Inside the bottle it behaves like lemonade, but from the user point of view it just needs a particular type of regulator. Under no circumstances use an ordinary regulator on an acetylene cylinder. One of the gases endearing features is reacting with Brass to form Copper Acetylide which is a sensitive detonating explosive. No joke if it explodes taking the top of the bottle with it – even a small cylinder contains enough to energy to destroy a workshop and burn the occupants.

Dave

[SamsarandaParticipant @samsaranda]

It frightens me when those with little or no knowledge state that they are going to embark on using acetylene gas for heating/brazing or whatever. Acetylene is a potentially very dangerous substance if handled incorrectly, the reason that numerous regulations exist about its control and usage and suppliers have in recent times tightened the supply of same. I have no issue with those who use it in industry and follow all the special precautions, I feel that it’s use by amateurs, as proposed on this column, should be strongly dissuaded, if you have ever had to organise the cooling of an overheated acetylene cylinder then you realise how close safe and disaster with acetylene can be.
Dave W

[nigel jones 5Participant @nigeljones5]

Totally agree with Dave W, unless you are gas cutting big chunks of metal or gas welding you dont want to be wasting a lot of money on acetylene, and you certainly dont want it near houses. If its in a fire and doesnt explode your neighbours will be forcefully evacuated for 48 hours (in UK), your home insurance is void and you wont be popular with the local fire brigade, police, neighbours and so on. Remember the M25 being closed in both directions for two days a few years ago? That was an acet bottle in a fire in a scrapyard near the motorway! Oxy prop is relatively safe and cost effective. You can buy new rerulators very cheaply – dont be tempted to buy second hand, too many out there never serviced and faulty. I bought mt torch and arresters second hand. Go for the small brass BOC type if you can, they are a lot lighter than most, and being vintage are well made of brass. This torch uses the smaller fittings (size eludes me – 1/4 bsp as opposed to 3/8 bsp? ). Make sure you get 6mm bore hose, it will supply all the gas you need and is a LOT lighter than the 3/8 bore. Trust me, silver soldering with the bigger hose is not fun. The nozzles which came with these torches were originally for welding and most of them are too small for my silver soldering needs…so I drilled them out a lot bigger. Using oxy/prop is a complete game changer. No faffing about with thermal blocks to keep the heat in – you obviously still need a hearth of some description. For my range of stationary and marine boilers mine consists of a single foot square of bbq lining board. No amount of heat will upset it and I simply move it to one side when im not using it. Always use T5 flux as its not worth risking the flux burning out before the job is complete. No silver soldering today, instead ive been annealing copper plate and pressing end plates. A big nozzle on the oxy/prop makes reasonably short work of it, even when youve got 60 to do. Hope this helps in some way.

Nigel

Pendle Steam Boilers

[Chris TickTockParticipant @christicktock]

Thanks Guys for the posts,

Having read your posts I feel confident I have made the right choice in oxy / propane. Still obviously lots to learn. One puzzle is why is silver solder sold in rods of varying thickness if it can only fill gaps 1 to 10 thou in silver soldering?

Also todate hadn't thought of a heath….something smallish any suggestions?

All equipment now on order short of solder & flux.

Chris

[Paul KempParticipant @paulkemp46892]

Bexley Heath, Hempstead Heath, too large?

Paul.

[SteviegtrParticipant @steviegtr]

My 1st job an apprentice sheet metal worker involved a full college lecture on gases. The Oxygen was usually at 2000psi full & liquid. The Acetylene was a spongy mass & much heavier to move & was 225psi. Then they brought in anti backfire arresters. Big signs saying no oil near oxygen. Learnt to braze gas weld at 15 years old it was a great 6 mths till I changed careers & became a Sparky. I never did any Silver soldering. Watched my mate do the boilers of his steam engines though.

[not done it yetParticipant @notdoneityet]

The Oxygen was usually at 2000psi full & liquid.

A gas cannot be converted to a liquid by compression. Oxygen is a gas at room temperature.

[not done it yetParticipant @notdoneityet]

Double post – deleted

Edited By not done it yet on 20/01/2020 22:25:57

[Anonymous]

The oxygen cylinder in my glider is at 2000psi and the oxygen certainly isn't stored as a liquid. When filling the cylinder at a club it is normal to use large oxygen cylinders, as used for welding, as these are normally at 3000psi when full. Mostly commonly three large cylinders are used in sequence starting with the one at the lowest pressure, usually below 2000psi, topping up with the intermediate cylinder and finally using the fullest cylinder to get to 2000psi in the glider cylinder.

At room temperature it is impossible to liquify oxygen by compressing it, as the critical point for oxygen is at -118.6°C.

Andrew

[RRMBKParticipant @rrmbk]

Take a bit of time to read the Workshop practice book No 6 by Tubal Cain , the late TD Walshaw . One will learn and understand all one ever needs to know about soldering, silver soldering and brazing and the distinctions between them. It may be dated in relation to its references to cadmium based products ( at least my older copy is ) but that doesn't in any way affect the superb explanations of the theory and practical aspects of this interesting and much misunderstood process. Happy reading and you will certainly achieve better joints after studying this straightforward and well written book.

It might be worth checking the acetelyne situation with your insurers. Mine immediately responded that my house and contents insurance would be null and void if I were storing acetelyne, even outside in a non attached building.

[Author]

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