Resistance soldering with mechanical strength?

I did a "duckduckgo" search for "friction welding brass" and got some very interesting results.

I can't say anything about resistance soldering to get the heat needed for silver soldering but since drilling, turning and pinning works I think that soft soldering would work just as well. Instead of a press fit you would need a clearance of .002" to .004". Then you could use a solder paste and either a torch or resistance to heat the part. Eric

I cut the end off a standard 200 watt soldering gun soldering element and used the posts as electrodes and it only took a few seconds to get so hot that it was more then sufficient ... I suspect it would work well on silver solder

You will still have some discoloration and flux to clean even if you resistance heat, but not as much as with a torch. For flux and oxidation cleanup on copper and brass I really like a mixture of 2 parts 5% vinegar and 1 part 3% hydrogen peroxide. Soak overnight in a sealed jar at room temp and rinse clean, or warm it up and experiment how long you need to soak.

I need to attach many many 5/16 brass threaded studs to 3/8 x 3/16 brass bars. There is an angle involved. I started out using jeweler's silver solder. It was plenty strong, but the fire scale on the threads was a huge headache, not to mention positioning. Now I turn down the end of the stud to

0.2 and press fit into a hole in the bar (which has a machined chamfer), and pin it. This holds well, but is a lot of work. Resistance soldering seems worth investigating, but most of the info I find on the web seems geared toward electrical and plumbing applications, not to mention the units are quite expensive. Is there a way to kludge together a system which will handle hard solder? Thanks!

A friend showed me how to do that with a standard Weller gun, and I can't wait to need to use it like that. It soldered a battery cable terminal on a 0 gauge cable in about ten seconds. I like it!

And I just learned it a couple years ago, from an old RCMer. I'm slowly learning what "precision" means in Glenn Neff's shop, as I do my larger metalworking projects. I'd be there more often, but he's down in Medford. I met him here, via Usenet.

Works a charm!

If it were one of my projects, I'd drill and tap the bar, apply solder paste (soft solder) to the stud, assemble, and apply a propane torch. You get extra points for drilling a tiny hole so the threaded socket doesn't build up steam pressure.

I recently soft soldered (60/40) using a paint stripper heat gun. It was copper pipe, but a wanted a flameless heat. It worked very well. I was a bit surprised, I didn't think it would get hot enough, it was plenty hot. Mikek

That sounds like a winner. I have to mill down the bar width anyway, and it could be easily done post-attachment. This would save me the operation of turning the 0.2 pin on the stud and machining the chamfer on the bar, not t o mention the pinning operation. Soft solder would be fine for strength in this situation. Tell me about the tiny hole. Where would I place it? Thanks!

it could be easily done post-attachment. This would save me the operation o f turning the 0.2 pin on the stud and machining the chamfer on the bar, not to mention the pinning operation. Soft solder would be fine for strength i n this situation. Tell me about the tiny hole. Where would I place it?

On second thought, that won't work. I misstated the bar width which is 5/16 , and that dimension can't be changed.

snip

Rob,

Would knurling the 0.2 stud end, and then pressing it in, be better? With some type of Loctite product maybe?

G'luck, PaulS

OK I might be worry about trapped flux... maybe I'd use a rosin electrical flux and not the acid plumbing type.

George H.

It's usually called a 'weep hole' the idea is that a closed pocket will collect flux and (under heat) build up steam pressure and expel material (spit solder instead of being displaced by solder). So you want a small vent on any blind hole. For appearance, it might be good to apply a solder mask (there are water-soluble paints for this) around that hole, and maybe on the stud threads outside the join zone.

If the parts are clean enough rosin core flux solder will probably work fine. You won't need a weep hole. Just heat the part and let the solder suck in via capillary action. Loctite was also suggested. In the past there was not a good Loctite product for brass. But I believe they make one now. If they do then that's the method I would use. Just a tiny bit of adhesive in each hole would be easy to apply. Eric

bars. There is an angle involved. I started out using jeweler's silver sold er. It was plenty strong, but the fire scale on the threads was a huge head ache, not to mention positioning. Now I turn down the end of the stud to 0.

2 and press fit into a hole in the bar (which has a machined chamfer), and pin it. This holds well, but is a lot of work. Resistance soldering seems w orth investigating, but most of the info I find on the web seems geared tow ard electrical and plumbing applications, not to mention the units are quit e expensive. Is there a way to kludge together a system which will handle h ard solder?

I used to (yikes! almost 40 years ago!) work in a shop that manufactured el ectronic products housed in deep-drawn rectangular section steel cans. The cans were soldered closed. We used a resistance machine to OPEN the cans by heating the whole perimeter at once.

The machine was a 5V 200A filament transformer connected to a fixture that held a pair of carbon blocks (about 2" x 3/8" x 1") in a clamping mechanism . You'd clamp the can between the blocks and hit the switch. In a couple of seconds the (soft) solder would be melted.

If, as some of the jerks there would do for fun, you left the can in the ma chine for a few seconds longer, you could easily get it glowing red. I'd sa y that ought to do the trick for your job.