ZDP-189
05-01-05, 05:13 AM
I'm no expert myself, but I have some experience here and am working on improving my technique. The following is a description of my current process which seems to work pretty well. It is posted here as much for peer review and comment as to instruct the people who need help.
Equipment
I just use a butane torch. It is the kind you see in cigar lounges that is a little bigger than the mini pocket ones. I have tried larger and smaller ones, but the flame on this is about right on the lowest setting.
In the past I have used silver solder chips or rod, but I find the silver solder paste from Sheffield Supply works best and contains its own flux.
Alternatively, you can braise, but the colour does not match the steel and nickel silver. Don't use lead solder, because the join is a lot weaker.
Preparation
The tighter you can make the bolster fit, the better. Solder won't wick into a gap wider than half a mm. If you get a force-fit, the solder will wick into parts where the gap is widest and along the join. That is what you want.
I use an asbestos braising mat under the vise, because I want to protect my work surface. That's especially important if you are a joiner or carpenter. Then I clamp the blade tip down with the vice holding the ricasso. This shields the blade from the flame and helps to sink away heat.
I used to use Block-It heat shield paste on the blade and ricasso, but it adds no value.
Soldering
I apply the solder paste onto the (clean) join and heat the tang just above the join. The heat will spread down to the join and the solder will amalgamate and run, wicking into the gap. Do not heat the paste directly, as the flux will boil, the solder will ball and you'll ruin the join.
Provided you work quickly and remove the heat as soon as you can, the solder should melt before the blade heats up enough to affect the tempering. There should be no oxidation discolouration on the blade at all.
Some people like to over solder the join and file back to a concave rounded join to the front of the bolster. I suppose that works and would add a bit of strength, but I like to add just enough solder to create just the finest bead, just barely visable. I have found running the tip of a nail, scribe or burnisher around the joint while it is up to soldering temperature will help to spread the bead evenly around the join.
Result
My objective is not to form a supporting structure, but to adhere the joint internally and form a watertight seal to protect the tang from rust over the working life of the knife.
Cautions
Soldering is obviously dangerous. All normal cautions, including the use of personal safety equipment apply.
There are some blades I wouldn't solder. Personally, I'd not solder damascus, as it's sure to need a re-etch. I also wouldn't solder a very small blade where the mechanical benefits of a solder join aren't material and where you could risk affecting the temper over the majority of the cutting edge.
Photos should follow next time I solder a bolster.
Equipment
I just use a butane torch. It is the kind you see in cigar lounges that is a little bigger than the mini pocket ones. I have tried larger and smaller ones, but the flame on this is about right on the lowest setting.
In the past I have used silver solder chips or rod, but I find the silver solder paste from Sheffield Supply works best and contains its own flux.
Alternatively, you can braise, but the colour does not match the steel and nickel silver. Don't use lead solder, because the join is a lot weaker.
Preparation
The tighter you can make the bolster fit, the better. Solder won't wick into a gap wider than half a mm. If you get a force-fit, the solder will wick into parts where the gap is widest and along the join. That is what you want.
I use an asbestos braising mat under the vise, because I want to protect my work surface. That's especially important if you are a joiner or carpenter. Then I clamp the blade tip down with the vice holding the ricasso. This shields the blade from the flame and helps to sink away heat.
I used to use Block-It heat shield paste on the blade and ricasso, but it adds no value.
Soldering
I apply the solder paste onto the (clean) join and heat the tang just above the join. The heat will spread down to the join and the solder will amalgamate and run, wicking into the gap. Do not heat the paste directly, as the flux will boil, the solder will ball and you'll ruin the join.
Provided you work quickly and remove the heat as soon as you can, the solder should melt before the blade heats up enough to affect the tempering. There should be no oxidation discolouration on the blade at all.
Some people like to over solder the join and file back to a concave rounded join to the front of the bolster. I suppose that works and would add a bit of strength, but I like to add just enough solder to create just the finest bead, just barely visable. I have found running the tip of a nail, scribe or burnisher around the joint while it is up to soldering temperature will help to spread the bead evenly around the join.
Result
My objective is not to form a supporting structure, but to adhere the joint internally and form a watertight seal to protect the tang from rust over the working life of the knife.
Cautions
Soldering is obviously dangerous. All normal cautions, including the use of personal safety equipment apply.
There are some blades I wouldn't solder. Personally, I'd not solder damascus, as it's sure to need a re-etch. I also wouldn't solder a very small blade where the mechanical benefits of a solder join aren't material and where you could risk affecting the temper over the majority of the cutting edge.
Photos should follow next time I solder a bolster.