Silver solder technique

[roweenie]

Has anyone here had any experiences/success in silver soldering together the ends of two separate pieces of the same diameter tubing (without using a ferrule or coupling)?

If so, could you share your technique?

Thanks!

[roweenie]

Thanks for the tips, Bloke.

My limited experience had me trying to figure out how to hold it all together from the outside. I hadn't thought of using a dent ball on the inside to hold everything together and all lined-up. That's a really brilliant idea.

(It's surprising how little info there is to find about this topic on the Internet.)

As to the amount of heat, is there any visual sign I can look for? My silver soldering experience is mostly limited to German silver rods, brace feet and the like. Since silver solder flux (borax) doesn't "flow" like soft solder flux (as far as I can tell), I have a more difficult time determining when to add the solder.

[Cameron Gates]

Could it be that Bloke said to form the ends with a dent ball, not hold them together with a dent ball?

[roweenie]

Cameron,

I certainly could be mistaken.... (it won't be the first, or last, time).

[roweenie]

Thanks Cameron!

What method do you use to keep those darned tubes perfectly lined up?

[roweenie]

Wow - secret AND low-tech at the same time!

Not to be nit-picky, but what do you like to lie the work down on? I have a steel plate that I've used for this purpose, but I have found that it makes it more difficult to bring the work up to the proper temperature for silver soldering, as opposed to the work being suspended.

[Dan Schultz]

I've been known to put round pieces in a lathe to perfectly align the ends while soldering.... one in the headstock and the other in a tailpiece chuck.

BTW... there are many different formulations of silver solder ranging from 3% to 45% silver. I've had very good results using the pre-fluxed stuff that Allied sells (part #A1080) but I don't have a clue what the silver content is. I normally use 33% silver (1/16" diameter) that I buy at my local Airgas store for heavy repairs like braces, etc.

Oxy-acelylene works best for me. It takes a bit of practice to determine just when to apply the solder while heating the parts. Once you have silver-soldered a couple of dozen scraps of .020" brass end-to-end... you are ready for the REAL parts.

There was a day when I could MIG-weld pin holes in beer cans!

[Dan Schultz]

There was a day when I could MIG-weld pin holes in beer cans!

Regrettably, you and I weren't acquainted during those days - as I had a considerable backlog of pin-holed beer cans that required those services.

[roweenie]

Dan, I hope you weren't welding up those pinholes while there was still beer in the cans (unless it was Rheingold, and then who cares?)

The solder I'm using is 35% silver, and like you Wade, I don't do enough of it to feel all that confident, especially a tricky joint like this.

Dan, the lathe idea is an excellent one. I dont have one, but if I did, I'd certainly give it a try. (Someday I'm going to break down and get one - I've always wanted a vintage South Bend 9" Junior, or something similar. Since I probably wouldn't use it as much as you pros, it's the one tool I've always wanted to "splurge" on, but just could never justify the cost).

[Cameron Gates]

Roweenie, how long are the 2 pieces of tubing and what is the diameter?

Dan's lathe idea seems like a winner, but I would think the pieces would have to be fairly long. My first thought was that, on a shorter work piece, the Chuck would suck up the heat and not allow the heat to be controlled at business end very well.

Dan, do you find that when using a BBb 3-jaw Chuck for this purpose that the actual jaw's contact point with the tube is small enough to not draw a good amount of the heat away?

[Dan Schultz]

.... Dan, do you find that when using a BBb 3-jaw Chuck for this purpose that the actual jaw's contact point with the tube is small enough to not draw a good amount of the heat away?

Give it an inch or so on either side of the joint.

BTW... all of my chucks are BBb. Do they make other keys?

[Doug Elliott]

Wouldn't a 3-jaw be in Eb?

[roweenie]

I seems to me it would be a pretty interesting lathe set-up to cut a half inch or so out of the middle of a tuning slide crook and braze it back together (in order to fit a slide to immovable geometry on a particular instrument without making a crook from scratch, etc.)

Bloke, you must be related to Karnak the Magnificent - this is exactly what I am (trying) to do, right down to the amount of material I'm removing.

[Donn]

All a "soldering jig" has to do is

- hold something still
- not become a serious heat-sink
- not catch on fire

If I were trying to butt two tubes, I'd think about a support that would hold them in place via gravity, a trough of some kind. Like a couple tubes wired up parallel. I'm assuming that the work doesn't tend to crawl around on its own, so gravity would be plenty.

If you had a lathe or some other way to do this somewhat precisely, would there be any point in trying to sort of mortise the joint, by tapering the edge? Taper in on one end, out on the other, so the joint sort of plugs together dry?

[roweenie]

Donn, believe it or not, the force of the flame coming from a torch is enough to move the item you are soldering, especially the heat involved in melting silver solder (@ 1125°F).

I'm sorry for asking what might seem obvious or simple questions, but my whole line of questioning is based on the fact that this kind of job requires extreme precision, coupled with permanent results. I want to "do it right" the first time!

[roweenie]

Excellent!

bloke "I told you there's always a reasonably easy way, and one that doesn't require a bunch of fancy $h!t."

THIS is why I come here to ask questions - what may appear to be "simple" to you pros, may actually be a major revelation to a challenged amateur like myself.

Thanks!

[Dan Schultz]

This type of thing is what makes repair work so interesting for me. Every job, no matter how simple on the surface, usually presents a unique oroblem.

Now that I understand what you are trying to do... I think I might just expand the ends a bit and insert a rolled piece of .010 thick patching brass inside to align the parts. Then apply the filler solder ... then sand the outside smooth.