Will soldering hold on bolsters?

I have seen photos from the good ol days, when they soldered with sulfur. When i dissembled an old knife with nickel silver bolsters I found that the bolster were almost hollow underneath, and the solder was only on the edges. They put a line of tin around the edge and sulfur in the middle, then placed the bolster on top with a clamp. I guess when the heat lighted the sulfur it worked like flux? Anybody heard of this old way to do bolsters?
 
I have never heard of using sulphur to solder. I doubt it was done that way.
If you are going to use heat to light sulphur, why not use the heat to melt the solder?
I often find little pieces of roundish matter under hollow bolsters. It took me quite a while to figure out it was polishing media from vibratory polishing.
Perhaps this is what you are referencing?
 
Bill DeShivs said:
I have never heard of using sulphur to solder. I doubt it was done that way.
If you are going to use heat to light sulphur, why not use the heat to melt the solder?
I often find little pieces of roundish matter under hollow bolsters. It took me quite a while to figure out it was polishing media from vibratory polishing.
Perhaps this is what you are referencing?
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I can´t say that I know it was done in that way, that´s why I asked :) It only looked like that in the pictures, and I kind of thought it made sense from how it looked under the bolster. They were heating the bolster just like we do, I will try to find that book and post pics. It was done in the early 1900s
 
Bill DeShivs said:
Because the bolsters are stamped out of sheet material.
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I did a translation from a text I found, it´s from Eskiltuna knife Museum:
"The jaws or fittings are pressed out of the plate and thus they become somewhat cup-shaped so that there is a gap between the jaw and the shell. This is for the soldering.
The soldering is done by clamping the back to the school with an iron wire clamp. With a small piece of sheet metal, salmiak is sprinkled on the soldering point and then the tip is dipped in molten lead, which sticks in the gap."
I was wrong in that it was sulfur that was used, it was salmiak. I did not know they used led, and I still find it strange that the gap of the old knives I have seen are empty, with only soldering under the sides of the bolster. You were spot on with the stamping :)
 
Salmiak is sal ammoniac (ammonium chloride). It is a solder flux used for lead soldering. It is also used to make fertilizer and medicines.

Leaving a slight domed gap on the back of soldered pieces was a technique to avoid solder starvation in joined pieces. The back was lapped to give a very tight-fitting surface to the piece it was being soldered to. The piece was fluxed and the solder or lead was wicked in by drawing toward the heat. Once cooled the joint was just a line on the edge but had more solder in the raised middle.
 
Stacy E. Apelt - Bladesmith said:
Salmiak is sal ammoniac (ammonium chloride). It is a solder flux used for lead soldering. It is also used to make fertilizer and medicines.

Leaving a slight domed gap on the back of soldered pieces was a technique to avoid solder starvation in joined pieces. The back was lapped to give a very tight-fitting surface to the piece it was being soldered to. The piece was fluxed and the solder or lead was wicked in by drawing toward the heat. Once cooled the joint was just a line on the edge but had more solder in the raised middle.
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Thank you so much for the clarification :) Except for that the bolsters were stamped, and therefor have a natural cup underneath, could this be a method of soldering bolsters today? If I would grind a "cup" on the underside, flux the pieces and just put a piece of tin in the cavity and heat it?
 
Yes, that will work.
You can also just grind some deep lines from the rearmost part of the bolster, and place solder on the liner. Heat, and the solder will flow under the bolster toward the heat.
 
The gap only needs to be sufficient to allow a good flow of solder. Excess is not needed and may cause problems.
0.01" is probably all that is needed. .030" is more than enough. As Bill suggested, I rough up my bolsters and other things being soldered on a coarse belt or with a file. That is usually plenty to allow the solder to flow.
 
Bill DeShivs said:
Yes, that will work.
You can also just grind some deep lines from the rearmost part of the bolster, and place solder on the liner. Heat, and the solder will flow under the bolster toward the heat.
Click to expand...
Thanx B! I just tried with only sanding both of the parts with 180g and put a line of solder in the back, worked really well. The solder flew under the bolster perfectly :)
 
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