I want to make some brass boxes, about 65x45mm, with hinged lids. I thought I'd use 2mm brass plate, and solder the bottom on with silver solder. They need to be oil-tight! I've not soldered brass before. Any suggestions?
IME its similar to soldering copper. So the usual rules apply: get the joint area mechanically clean first (wire wool etc), use a flux (ordinary plumbing fluxes would be ok), then heat and solder once both surfaces are up to temperature (which will depend on type of solder selected)
Cleanliness, Easiflow No 2 and a good heat should do it.
2mm sounds a bit thick for some thing quite small. Think I would use thinner plate and fold the sides up so that you have a mechanicaly stable box with minimal gaps at the corners then just solder the seams.
A loose base and sides I can envisage being a nightmare to solder unless you can hold all the bits in place and do it almost in one hit. Even with folded loop sides and loose base might be fun.
Just like soldering copper. Not a problem.
Its fine. Use plumbers flux and a BIG iron or small blowlamp.
The original is cast brass and is 3 to 4 mm thick:
I thought I would have the base and back in one piece and the other three sides as another piece.
a duplicate for some where else?
Makes the folding easier if nothing else. You can probably tack solder that those two peices into a mechanicaly stable object then solder along the join in a single pass with a small blow torch. Or you could try brazing it, which would be stronger than soft soldering.
When I was about 11 or 12 we did silver soldering for jewelery at school (no precious metals or stones involved though :-) ). ISTR having three or four different grades of solder so you could start with the highest and work down to do several joints without melting the previous one.
Wouldn't be allowed now, of course, and I'm only 27.
Pete
Soldering small brass boxes can be problematic in that the joint you're working on ideally needs to be horizontal. Sooner or later it'll be sod's law that there'll be an adjacent vertical soldered joint - and before you know it all your solder will run out of it unless you have a very good gas gun that delivers an accurate flame and you're very quick with your hands. I'd use a paste flux, such as La-Co, as it offers some slight cooling over previously soldered joints and won't contaminate the joint you're working on if it runs down.
If the box has to withstand a hefty kick I'd be inclined to silver solder it - 2mm brass isn't going to give you enough surface area to ensure the joints won't give way if one of the sides cops a whack straight on. You'll need to get the brass up to red heat, but as silver solder doesn't flow as freely as soft solder you won't have quite so many problems with unsoldering joints. If you're canny you can use a couple of sticks of solder with different melt points ( use high/low with adjacent joints ). A small tub of JM tenacity No6 powdered flux will last you almost a lifetime.
Regards,
Matty F submitted this idea :
Brass is easy to solder, but you might be in bother holding the corners in place. 2mm in such small pieces might be impossible to fold to provide an overlap, so could you use some thin ready made brass angle in the corners? Model supplies type places would have the angle in stock.
First of all, soft or silver? You'll have a pig of a job soft- soldering lubricators like this, because of the thickness of the brass and the amount of heat you'd need to apply.
If you do go for soft, forget irons, forget torches, and go for sweating them together.
This is basically heavy tinning in the joining areas, assembling cold, dribbling liquid flux in (Baker's fluid) and then heating slowly in a furnace (or best approximation with a few firebricks and a broad torch flame), until the solder runs together. You're reliant on capillary action here, and no amount of faffing about with an iron or individual jointing with a torch will give you a reliable leak-proof joint in thick brass.
Mechanical fit is important. It's too thick to fold and yet get a square edge, so you're building up from flat sheets. I'd leave the front, back and base over-long, then file them down into your cuboid afterwards. I'd also use a tiny chisel to raise a few tiny burrs on the inside of the base as a backstop for the sides, then wire the box up with soft iron wire before heating. You can even use iron toolmaker's clamps inside (whitewashed to stop them sticking), or even (easiest for bulk runs) make up a welded or ground steel inner scaffold block (with big chamfers) so that you can clamp the brass plates easily into place onto it.
Personally I'd silver solder it. Viscosity is lower and capillary attraction greater, so it just loves to flow nicely and give a well- sealed joint. Again, pre-build the load and furnace it, rather than taking a torch around inch by inch. Silver solder is expensive (but so is time), so make the parts fit well. Again, I'd make the edges straight, stack the box up with overlaps, solder and then trim afterwards.
Brazing is possible, looks good (colour match), but hard work. You have a tiny (if any!) difference in melting point between a hard sheet brass and a soft spelter.
Cleanliness beforehand is important. If you have any lead solder around, stick with using lead, as silver soldering over old lead residue is a right old pain.
Silver solder used to (and bought via eBay still does) contain cadmium, which makes it easier to work with and the fumes toxic. Silver soldering flux (Easyflow) is fluorides, so that's pretty nasty when heated too. Ventilate!
You need a firebrick hearth and plenty of bricks around it before you do any of this stuff. Firebricks are cheaper than bigger torches and encourage more even heating, with less distortion.
In message , Matty F writes
I offer this just for interest, but it might be relevant.
When we built the yacht in the garage, I took the door off an old fridge, folded a piece of brass to be easy to clip over the bottom of the icebox and soldered mainly copper tube offcuts, but all sorts of other junk to it. A sheet of polythene guided the dripping condensate into the salad tray at the bottom, which was emptied every evening.
This was my attempt to dehumidify during the build.
Towards the end of the 5 years the copper tubes started to fall off. Inspection showed that the solder had changed to what looked like a crystalline form - sort of like a really terrible dry joint, but much more obvious.
Not certain what caused this. I don't think it was due to anything like different expansion/contraction rates between brass and copper, as the fridge just ran continuously for the whole 5 years. It might have been long term vibration in the cold.
That box is similar to the four that I need to make. I'm still waiting for photos of the original.
Hah! I better investigate brazing. I'm tempted to have a look at getting it cast in a foundry. This may be harder than I thought.
In message , Matty F writes
Should be a piece of cake to solder, silver or soft. Brazing is a different matter, IIRC you're risking melting the workpiece when you reach the temperatures required if it's made of brass.
Brass is a doddle to solder given sufficient heat, all you need to do is assemble the box and wire it together using steel wire. Nothing to say you couldn't use some brass machine screws to hold the box together and then file the protruding bits off later either!
If you can anneal the brass and fold shapes to form a box then it becomes easier still. You can even cast brass at home if you are sufficiently adventurous, I quite fancy having a go at lost wax casting.
Web search for "grey tin", and the story of how Napoleon was defeated in Russia because his army's trousers fell down.
Brass is a pig to cast. Bronze is _so_ much easier.
This wouldn't be an easy shape to cast, as you have to flow into those deep, thin sides. Not a hard bit of patternmaking, but I'd use Petrobond sand (by the kg from mutr.co.uk) and a traditional open mould, not my usual lost foam.
Apart from lost wax, the "lost frog" process is amusing...
Hmm Wiki states that bismuth or antimony may be used instead of lead. Bit they are ,are they not, aabout 1000 times deadlier than lead?
The same could be said of the mercury in amalgams - the fact that it is alloyed no doubt reduces the potential for harm.
Copper or silver and copper seem to be the alloys of choice these days for eutectic lead free solders for electronics etc. Some plumbing solders (particularly in the US IIUC) go for antimony.
Maybe - I really don't know - but medicines such as Pepto-Bismol contain bismuth subsalicylate. And bismuth-containing medicines were used by Dr Barry J. Marshall and Dr J. Robin Warren in their work on Helicobacter pylori.
And your self-same source says this of Bismuth:
Scientific literature concurs with the idea that bismuth and its compounds are less toxic than lead or its other periodic table neighbours (antimony, polonium)[22] and that it isn't bioaccumulative. Its biological half-life for whole-body retention is 5 days but it can remain in the kidney for years in patients treated with bismuth compounds[23]. In the industry, it is considered as one of the least toxic heavy metals.
I really cant see soldered 2mm brass doing that.
NT
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