Silver soldering Torch size

I am going to need to silver solder some pieces of 30mm x 30mm x 5mm mild steel angle to create a frame for my clock project but have (as yet) no silver soldering equipment or experience.

Can anyone with experience suggest what size (Kw) nozzle or torch output I am likely to need to be successful. Is the (probably 900w) MAP type torch from Toolstation going to be sufficient. I suspect I don't need a big (7Kw) Sievert, but what sort of size in between would experienced users recommend?

A forget silver solder, use brass, Sif bronze No1

B forget MAPP use propane and a 1"dia burner with a brazing hearth ! You will need LOTS of heat, far more than I think you realise

If your any where near me you can use my gear .Noel.

The Rothenberger or Bernz swirl burner on MAP gas is nearly 2kw.

900W sounds like an ordinary neat butane paint burner torch.

Screwfix gives you more specs than Toolstation.

The map one would do it providing the work is stood on a fire brick or some Rockwool (not fibre glass) and not clamped.

I agree about the torch size and propane use. The Toolstation Map torch isn't up to it. Not a 100% in agreement with Noel about silver solder or Sifbronze. I use both methods and would probably Sif bronze this job as Noel suggests. However you need a higher temperature for Sif bronze, so a high silver content solder may prove to be easier for a beginner.

You won't need much silver solder or Sif bronze and I think that appropriate fluxes may cost more than the filler rods!

Andrew.

I'd be looking around 7Kw which is the standard Sivert size when you buy a starter set, it will get things upto temp quickly without risk of exhausting the flux. You don't say what lengths your angle iron is but thw longer it is the harder it will be to get the thing upto temperature with a plumbers torch.

I'd also go with silver solder as it has a lower melting point than the Sif. use a high temperature/long lasting flux such as HT5

That's what I use for all my steel fabricated model parts

Edited By JasonB on 21/10/2022 13:02:47

Thanks,

Looks like the wallet moths are going to have to be prised out and a "proper" torch and accessories acquired.

I suspect I will use a lot more silver solder and flux practicing than the job will need. Thanks again.

If you do go for the propane option I keep a 3.9kg cylinder in to run it off but if I have a large job or jobs coming up I have swapped it for a 6kg cylinder which lasts longer and is better with a 4bar regulator but a lot bigger to keep in the garage. There is no charge for swapping sizes within the same group and as I have no big jobs coming up I have swapped back to the small one to save space.

Also there are shortages of some cylinders for new purchase so I would find that first - the torches are easy to find!

Edited By Nick Clarke 3 on 21/10/2022 15:47:41

In view of the cost of setting up for materials and equipment for Silver soldering, may I suggest paying some one to tig weld it for you. John

Peter why not prep your frame/stand then take it to a local man who makes gates etc, he would most probably Mig it for a drink.

Anyone with a welder should be able to it. Tig welding would make a nice looking joint that won't need any grinding.

Bernard, Nicholas,

Thanks for the idea. I will walk down the village to the local agricultural engineers and see what they say. Even a paid for job would probably be a lot cheaper than a full sievert torch kit, gas and materials to practice with.

But then I will have lost a new skill learning opportunity! To be thought about.

A decade or so ago I brazed the frame of a wheelbarrow using a MAPP torch and sifbronze. It was on the limit of the torch. Not helped because I left the barrow body in place to keep it aligned. This increased the heat sink, and I burnt off a small amount of its galvanizing. It would have been much neater had I had access to oxyacetylene, but it has held better than the original weld.

My first thought was, why would anyone think about silver soldering 30x30x5 angle iron ?

Surely that would be a job for a welder, Mig or otherwise, both quicker and cheaper.

Many moons ago, I did silver solder 1/2" round MS bars, using two blowlamps, seemed to take forever !

Take it to a welder.

Probably less risk of distortion as the weld cools, very small neat fillets and a welder may cost more than a torch etc if you don't have either. Then there is the "I made it myself" factor to be considered.

I've certainly silver soldered angle into fabrications, it can be handy when you ar ejoining multiple parts as it's one less joint if you need a right angle and sometimes the large internal fillet can actually be an advantage.

This bit

Is what goes below the finned cylinder and then down to the base

As the angle is probably part of an assembly much like this it is also a lot easier to get solder to flow into all those joints than trying to get in there with the end of a MIG or TIG nozzle an no need to do weld prep on all the joints.

Edited By JasonB on 22/10/2022 08:51:08

I think getting the local blacksmith to TIG (or MIG) these steel parts sounds like a good option and he probably wouldn't charge you the earth for it. You may be able to return the favour one day - I've made odd sized bolts for a welder friend of mine.

For small steel fabrications I use SIFbronze and a Bullfinch 404. I do use silver solder but I'm trying to hoard my supplies of that for obvious cost reasons (SIFbronze is very much cheaper). The Bullfinch can handle 'bronze' brazing (e.g. brass brazing) as well as silver brazing of course. I don't use it for boiler work but it's ideal for small fabrications. It's a very well made tool that will last, so one of those things that really is a good investment.

Regards,

IanT

PS That baseplate is about 50mm square and 3-4mm thick...and yes, I did re-do that bit I missed on the side!

IanT

Jason's point about soldering, instead of welding, small but complex fabrications is a good one. But doesn't soldering demand tight fitting, properly cleaned joints? Successful welding has the same requirements.

I would suggest that if Peter presents his parts as above, with all the scale ground off a welder would have them finished in less time than it would take to heat just one soldered joint. And they're 5mm thick, which is well into stick welding territory not just Mig or Tig.

Thanks again, I will have a rethink. I have never tried to fabricate parts on this scale before. The thing I am trying to make looks like this (ignore the vertical lines on the faces the are artifacts of the way it was constructed in the modelling tool - three separate trains). It's about 350mm long and 140mm wide. The sides are 30mm deep, and I plan to cut one side of the 30 x 30 x 5 angle down to 12 mm for the top faces.

The real thing is one single lump of cast iron about 5ft by 2ft and 3/4" thick but creating a pattern and getting it cast is a big step too far in my learning. I visualised shaping the four main sides and silver soldering the corners, the feet can be made out of the same angle and attached in the same way.

The discussion of welding in the thread has helped. Any weld fillets could (would?) be inside the frame and hence invisible.

So, thanks again the help around here is terrific. I will investigate the possibility of getting it welded.

Typo

Edited By Peter Cook 6 on 22/10/2022 11:55:41

And brazing keeps the workshop warm in winter ! Keep the lighting level low so that you can see the temperature of the joint as it comes up to silver / bronze brazing temperature.

Bob

The weld need not show, you would do some weld prep (chamfering the corners) so that the weld filled the resulting V when the two parts are brought together and then file or grind it off flush on the outer faces.

At that sort of size I would be 50/50 to weld or solder, either way allow for taking a skim off the feet and then the top face of the frame to make sure all is flat and true.

take care if brazing or soldering in the workshop as you don't want to gas yourself and the moisture from burning propane can condense on all that cold metal machinery.