Soldering brass

[jhmiii]

I need to silver solder brass to brass. Will the solder also attach the brass pieces to the steel jig holding the brass pieces in place?

Twelve brass pieces are to be connected end to end in the shape of a dodecagon. They need to be accurately located and clamped in place. I am planning to make a steel jig for this purpose. The jig consists of a flat square plate as the base with a flat disk (diameter equal to the inscribed circle of the dodecagon) bolted to the base. The brass will be laid around this disk. Holes will be drilled and tapped on the base for clamping the brass pieces. Consequently, the brass will rest on the steel when soldering. The acidic flux will probably pit the steel. Anything else I need to look out for? I have only minimal experience soldering and previously have been able to hold the parts at a distance from the soldering action. The way I silver solder is as follows: the brass pieces are clamped about 2 or 3 thousandths apart and fluxed, two or three tiny pieces of solder are placed on the joint, and the brass is heated on both sides of the joint with a propane torch until the solder flows into the joint.

I don't want to buy the steel (1/4" X 10" X 10" base and 1/4" X 8" X 8" disk) for the jig ($50) until I am sure this method will be successful. A different jig approach making one joint at a time was not accurate enough to ensure the final two ends would meet appropriately. Thanks for any and all suggestions.

John

 

[David S]

Hi John,

Do you have a picture of what you propose? Also when you say silver solder, are you using high temperature silver solder as in silver brazing?

I am just thinking that the steel may act as a heat sink and may make it difficult to braze with propane.

David

 

[chips&more]

Silver solder will stick to steel and brass.

 

[aliva]

I wouldn't worry too much as the brass will heat much faster than the steel and will accept the silver solder first. The steel would have to be heated much more than the brass before it would solder. Heat the top of the brass furthest away from the steel. Solder the top portion of the brass, let it cool and reposition to solder the other side of the brass. As David S suggested a picture would certainly help in determine the best procedure.

 

[T Bredehoft]

the steel may act as a heat sink

I'd suggest making your disc have the appropriate number of flats on it. with notches at the corners so that the steel is not touching the brass at the joint. Ditto, the base plate with a cavity under the joint. Less possibility of heat sink effect.

 

[RJSakowski]

One trick that jewelers use when assembling multipart works is to use progressively lower melting point silver solders. This decreases the possibility of melting a previously soldered joint. Also, using a pencil flame oxypropane torch will permit a concentrating the heat in the area being soldered and not having the heat flow to previously made joints.

 

[Colin Creed]

Hi John,

Being that I'm an old Jeweller, I can think of a number of ways to tackle your job, but most would require a certain degree of jewellery skill & knowledge.

Silver solder ie; "silver brazing alloy" will bond onto steel if the flux is present on that steel.
And as noted by others within this thread, steel will act as a "heatsink" when trying to solder.
Maybe consider looking at a Jewellers Supply for what's known in the Trade as a "Solder Mat"...
...it's a non-asbestos board that can take extreme heat & is flat. https://www.amazon.com/dp/B06XVHKTKN
Charcoal blocks are another option & they're soft enough for you to either use pins to retain parts in place or even press the parts into the charcoal block to create a simple "holding form" while items are soldered together.

One simple Jewellers trick is to mix up a paste made from polishing rouge (typically the red as it's finer) & water, then apply this to areas where you DON'T want the solder to run.
In your case this would be where the steel disc contacts the brass pieces.
If possible, first apply the paste onto the disc & warm it to evaporate the water, leaving the dried rouge as an oxide layer, DON'T remove it.
Even just heating the steel so there's an oxide layer on it will/would most likely work.
(silver solder doesn't like oxidised material & so wont bond very well even with flux present)
Then arrange your brass items into place & only apply a small amount of flux, then warm the flux so its water content is also evaporated away from the brass pieces.
From that point you should be able to apply your small "panels" of solder into place with a "solder pick" or with tweezers then heat until it runs.
Remember too that silver solder will be drawn to the hottest point & fills joints using capillary action, so use the heat to your advantage.

HTH, Colin

 

[jhmiii]

First off, thanks to all for their responses. I have attached a picture of a previous attempt where my jig held two pieces at a time. This was the final joint on the first dodecagon. The dodecagon closed, but was not completely flat. The second tried this way did not quite close and had to be sanded and then was not flat. Cumulative error!!! So that is why I need to lay out all of the pieces at once and make sure they are correctly aligned before I solder.

Replying to some specifics: I use low temp solder. The brass is 3/16" thick so the solder pretty evenly flows into the complete joint. I don't think I could accurately machine flats on such a large disk, but like the idea of making slots in the base that align with the corners of the dodecagon. I also like the idea of providing a barrier between steel and brass, oxidation or rouge. A pencil flame torch would definitely be a help as it is difficult to keep the flame only near the joint.

One further question. Does most of the previous discussion also apply to an aluminum jig as opposed to steel?

Thanks for all of the helpful advice.

 

[T Bredehoft]

Aluminum vs steel? No, aluminum won't take solder, but it is a fabulous heat sink. It will suck the heat out as fast as you put it in.

 

[David S]

Now that I see the size of your project it would be too large for the jewellers soldering blocks that I have.

For the base you could look at fibre cement board. You may be able to get a small piece from a local fireplace installation company. The stuff that I had was flat and heat resistant and won't act like a heat sink like steel or metal. You should be able to cut it to the base shape and then clamp to it.

David