Joint Design - Silver Soldering

[Runner]

Hi all,

I need to extend the length of a 2" dia gunmetal rod by 1/8th". I have faced in the lathe the two mating faces and intend to silver solder them together. However, the silver solder needs a small gap to penetrate between the mating surfaces and I am depending upon the tool marks made during the facing cut to achieve this. Is this sufficient and or do I need to a different joint design other than face to face contact.

Thanks in advance,

Brian

 

[GWRdriver]

Brian,
The usual trick is to raise some metal by putting in a few symmetrically located center pop/punch or prick marks. The next question for me is how do I insure solder gets to the middle. Your job may not allow this but if I have such a situation I consider using a very small central solder feed hole.

 

[chipenter]

If you cut off a small piece of silver solder and put it in the centre with plenty of flux , apply heat and the solder will go to the hottest part just move the torch round and the solder will follow , you can see the solder in the joint , you shouldn't need to make any pop marks as the solder will find its own thickness .

 

[Runner]

Thanks Harry and Jeff. I was less than precise in my original description, its not a solid rod it has a 1 5/32" bore, so if I apply the silver solder to the outside of the joint I should see it wick through to the centre if all is well.

Brian

 

[GWRdriver]

Brian, you shouldn't have any problems. When I do similar assemblies I will turn one of the mating faces with a very slight relief angle, to give the solder an entry point and flow channel.

 

[Runner]

Harry everthing went fine. A 2" dia x 2 5/16" gunmetal rod even with a 1 5/32" bore requires a lot of heat to bring it to temperature for silver soldering. The required OD is 1 5/8" so I decided to machine it down to near the required OD so as to make the assembly easier to silver solder. However I left the 1/8" piece at 2" dia and stood the larger piece on this to form a top hat assembly. This enabled me to easily run the silver solder around at the junction of the two pieces. Your idea of using puch marks on the mating faces did the trick and wicked through like wildfire.

After machining both the OD and ID you can't see the join.

The only downside was the amount of gunmetal I had to machine off and therefore waste, now going to landfill.

Brian