School me on solder

J

Jason Fry

Knifemaker / Craftsman / Service Provider
Joined
Jun 5, 2008
Messages
3,159
I need to either braze or silver solder a joint. Several questions... Can either of these be done with a propane torch, or do I need Mapp or acetylene? Where do you get silver solder or brazing rod? What kind of flux do you need?
Thanks!
 
What type of metals are we talking? That can make a bit of difference in the answer. For soldering smaller parts you can make do with a handheld propane torch, but for brazing you generally need fuel and oxidizer.
 
For my takedown project in the other thread. Attaching either some mild or allthread to CM154.
 
Jason Fry said:
For my takedown project in the other thread. Attaching either some mild or allthread to CM154.
Click to expand...

Cleanliness is everything


On stainless steel, something like Staybrite is popular.
Get the flux that matches the solder


For a low strength sealing like a guard, you can use low temp silver solder maybe 435 degrees F steel to steel or steel to brass
I find my local hardware store has small kits.


The stronger the solder for a stronger joint, the silver content goes up and the temperature goes up.
Then they call it silver brazing over silver solder


I think it's important to use some sort of keyhole or dovetail joint that provides a mechanical connection.


Check out jewellery or welding suppliers catalogues and read all the specifications
There are dozens available.
 
I've got the staybrite, and was planning a mechanical dovetail also. It will all be epoxied inside the handle, so it's not like I need to pull a Mack truck with it. On the other hand, I want it to be right, not just thrown together.
 
I'm guessing that the blade has already been heat treated? If it has, with the dovetail, then JB weld will work and you won't have to heat anything. Otherwise, the staybright won't hurt your temper. If I understand your idea, the biggest part of doing it right is a good fit on your dovetail.
 
Brazing silver is in the 1200f range, and since you are using stainless, you can't use brass or bronze. You can use nickel silver if you want to heat a bit past 1600f. Oxy acetaline is preferred for brazing but propane would be fine for soldering. If you want to braze, I can look up the fluxes I used when brazing bicycle frames.

I remembered the site I got the flux and rod from: henryjames.com
 
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Jason to be done right its going to be silver brazing. Example, you wouldn't silver solder
say a nut on a pommel and expect it to hold, one good rap and its off. You can do it any
way you want since it will be internal. You did however state you wanted to do it right and
no amount of cleaning or silver soldering is going to give you the strength of sliver brazing.
Ken.
 
What I do to attach a threaded rod or other extension to a stainless tang is weld it on with a MIG wire welder. I know the welder guys will freak out, but I just use the regular wire for general welding, even if the tang is stainless. The rod is usually just some thread-all, but sometimes it is a shaped piece of steel with the end threaded.

I clamp the blade between two pieces of steel to keep the weld spatter off the blade, and weld away on the tang. After the weld, I dunk the blade in water up to the ricasso to keep any heat from bleeding into the HTed blade, but not up to the weld joint, as I don't want to "chill" the weld. I then temper the blade one cycle at 350F to make sure the weld isn't brittle. After some grinding to remove my ugly weld excess, the tang has a solidly attached extension.

My normal method for attaching the rod is to cut a 3/4" long slot in the tang and set the rod in the slot. A few hammer blows and the rod will fit the slot snugly. Then I weld up the rod on both sides. After the temper, I grind the rod flat to match the tang thickness if necessary. Most of the time, I use 1/4-20 threaded rod.
 
I prefer a lap joint, pinned and silver brazed. I don't have welder. Brownell's Silvaloy 355 is strong and easy to work with, and for a threaded rod tang extension, propane will get it done.
 
I have cut a slot out, tapped it, the screwed the all thread down into it, no heating required, when i fill the handle with epoxy it sets around the join as a extra hold.
No issues yet and i build knives that are regularly used by deer hunters.
 
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