silver solder clearance

[jdunmyer]

If I have a round part that I want to silver solder into another part, how much clearance should the hole have? Assume that the round part is 1/2" diameter. Would it be the same for a part that's a bit over 1" diameter?

[JCHannum]

Silver solder needs about 0.002-0.003" clearance for capillary action to draw it into the joint. That would be about 0.005" oversize on the diameter. It is the same regardless of size.

Lightly centerpunching the male part around it's circumference will help hold it on center and maintain equal clearance between the parts.

[SGW]

It depends in part on what alloy of silver solder you're using. Some flow better than others. In general though, I'd probably leave about a thou or two clearance for a free-flowing silver solder.

If the assembly doesn't have to withstand heat during use, have you considered Loctite 609? If you have a decent amount of surface area in the hole, that might be an alternative way to do it. Leave about a thou clearance for that, too.

...or there may be other opinions...

[Mike W]

I used to make long drill bits by drilling a 1/4" hole in the end of the drill and then silver soldering a length of 1/4" music wire into the hole. I never had one of those joints fail.

[lazlo]

Silver solder needs about 0.002-0.003" clearance for capillary action to draw it into the joint.

Geo Thomas' book also recommends light axial scratches down the male shaft to encourage the capillary action. I just did this on a piston assembly and it worked nicely.

By the way, MAPP really sucks for silver soldering (brazing). I really need to get an oxy rig...

Lightly centerpunching the male part around it's circumference will help hold it on center and maintain equal clearance between the parts.

That's a very cool tip JC!

[Mcgyver]

[QUOTE=lazlo]
By the way, MAPP really sucks for silver soldering (brazing). I really need to get an oxy rig...
QUOTE]

lazlo, don't know much about MAPP gas, but imo something like propane is a lot better than an oxy rig - oxy acetylene for example is just too hot for ss, its too easy to mess up the flux. I know it can be done, using heat indirectly, and is necessary to get enough heat if the parts are large, but imo propane is a lot easier in 95% of the cases. best set up for me is three refractory bricks form a corner, they do a great job of reflecting the heat back

another trick for providing cylindrical clearance but keeping things aligned, take the male part and using the edge of a coarse file, roll the part along a bench will pressing down hard.

best solution though imo is to figure out how to pin or screw the parts together (as so well illustrated by Kozo) or make a universal fixture or third hand - here's mine.

http://i20.photobucket.com/albums/b2...0/3e5f7733.jpg
http://i20.photobucket.com/albums/b2...dcloseupII.jpg
http://i20.photobucket.com/albums/b2...rsoldering.jpg
http://i20.photobucket.com/albums/b2...ethirdhand.jpg

[BadDog]

Nice. Now you've given me YET ANOTHER PROJECT...... But nice none the less...

[lazlo]

By the way, MAPP really sucks for silver soldering (brazing). I really need to get an oxy rig...

imo something like propane is a lot better than an oxy rig - oxy acetylene for example is just too hot for ss

Hmmm, I didn't know that. So you have an oxy rig (regulators, tips, etc) and run it with propane instead of acetylene?

If I get T-rated hoses, can I switch back and forth between acetylene and propane?

By the way, the really stupid way I've been centering the male part when silver soldering: I leave enough meat on the female piece, braze it together with the male part as close to centered as I can get, and then chuck the whole thing in the lathe and turn it to the male piece

Gotta try the center-punch or file trick

[vmil3]

Yes,
Thats correct, T type hose is for all presently used fuel gases, where as R type is for Acetelene use only.

[Mcgyver]

lazlo, didn't mean to imply i'm using oxy/propane, its just plain propane I'm using. picked up a torch and regulator years ago from a welding supply place that just screws on a regular 20lb cylinder. I have O/A and have used it for silver soldering (applying the heat indirectly), but more often than not I'll braze if the work is big enough to drag out the O/A. using the three refractory bricks, its amazing how much heat you can get out of propane. On the other hand, if the work is large and you must silver solder, the flux doesn't like to bake for too long so you may be stuck using O/A to ss the large assemblies.

Either will work in the hands of the experienced, but if someone is new at it I think they'll have more success with propane.

gawd, I'm sounding like that bad tv cartoon about the propane salesman