No wonder people can't solder!

Bill DeShivs

Bill DeShivs

Knifemaker / Craftsman / Service Provider
Joined
Jun 6, 2000
Messages
12,771
I just happened to type "soldering knife guards" in on You Tube.
Sweet Jesus! Don't do it the way ANY of the guys on the first page do it!
Yeah-I know there is a big name there.
It's not rocket surgery....
You don't need acetone, alcohol, oxy/actylene torches. You don't use solder by the foot!
Most of these people have no idea about heat transfer.
All you need is clean metal-I don't mean clean like washed. Just file it to bare metal-that's all.
Learn the difference between a heat-reflecting surface and a heat absorbing surface.
Flux the joint. You can use pencil, grease, ochre-lots of things to dirty up where you DON'T want your solder to flow. The flux is an acid-you don't want to apply it until it's running out of the joint. It will etch metal.
You can use a standard propane torch, MAPP gas, air/acetylene, or O/A torch. It doesn't take much heat at all to flow low temperature silver-bearing solder. A heat gun is a bad idea-it heats too large an area, too slowly. Solder flows toward the heat. Don't keep applying flux while hot and wiping solder all over the guard and blade.
Use the vise as a heat sink to keep the blade from getting hot. Wrapping your blade in aluminum foil won't do the trick!
Use only enough solder to fill your joint. Place the solder piece(s) on the joint and heat with a torch until the solder flows. Remove heat. It's that simple. Don't glop the solder on until it runs out of the joint and down the blade. When using solder. less is more.
Adding more heat will accomplish nothing except ruining your joint and screwing up your blade.
Once the joint is made and solidified you can stick the whole thing in water to cool it. Putting a little ammonia in the water will help neutralize any residual flux.
 
The enemy of soft soldering is HEAT. Except for jewelers, most folks don't have a torch SMALL enough for soft soldering on knives. I teach people using a $15 small refillable butane torch from Home Depot. ( I am going to teach someone this weekend, maybe I'll do a tutorial while there since there will be a second person to take photos.)
As someone who hard solders and soft solders every day, it is all about heat control. You want the heat for either task in the largest/thickest/innermost part of the joint -The blade in soft soldering a knife, and the barrel in hard soldering on a front sight on a barrel. The solder will draw toward that place once the heat gets to the joint on the thinner part. It doesn't take a lot of heat to melt and flow the modern soft solders at 275-400 0176F. It also doesn't take a lot of extra heat to burn the flux and make a joint that won't solder. With some practice, you can soft solder with a heat gun.

I agree with mete. There seems to be a lot of confusion from people who have seen high temperature silver soldering (hard solder) and try and use the technique to do low temp silver bearing solder (soft solder). Plus, the alloy in the low temp stuff has changes over the years as they removed lead and replaced it with things like indium/gallium/tin/etc.

If you want reasonably strong and easy soft solder, use TIX. I melts at 275°F and is almost foolproof. They sell their own flux (really good) and even sell small bottled of yellow ochre for anti-flux.
 
Bill DeShivs said:
I just happened to type "soldering knife guards" in on You Tube.
Sweet Jesus! Don't do it the way ANY of the guys on the first page do it!
Click to expand...

I think you just volunteered to do a video :) Honestly what you would put up would be of great value, I am starting my study into making slip joints and who better to show how so solder bolsters then Bill DeShivis ?;)
 
Just a FYI, that “big name” doesn’t solder his guards. He press fits them and his tutorials are pretty good.
 
Yeah, I'll take the video camera and have Steve film the whole demo with commentary.
 
I'll add this again - for soft solder and braze the strongest and best capillary gap is 0.003 "
 
Any way to avoid a silver solder line at the guard joint? This is one of the reasons I’ve never tried learning this technique.

I’ve also always wondered about the risk of galvanic corrosion (for example, a copper bolster soldered to a carbon steel kitchen knife). I figure if you only use epoxy than the two parts are insulated and you prevent this, but if the two are joined by electrical conducting solder, does this become a problem?
 
Stacy is probably in a better position to do a video. I seldom make fixed blade knives- 1 or 2 a year, and we are caring for an ill relative.
I'll comment and try to help, though.

Re- Galvanic corrosion:
Your metals are already touching. If they aren't your guard needs to be fitted much tighter. Solder won't make any difference.

Stacy's recommendation for Tix Solder is a good one. It's expensive, but very easy to use.
 
Galvanic corrosion is a big deal in things in or filled with water. It isn't an issue with dry metal surfaces in contact with each other.

One thing that does cause problems is not fully rinsing and neutralizing the flux. It needs to be washed out of all crevices on both sides of the guard. Boiling it for 10 minutes in a pot of water with a tablespoon of baking soda added is a good way. We jewelers have 100 PSI steamers to take care of that, but I still scrub with baking soda and water before steaming.
 
There was really a video where the guy had his blade wrapped in foil while soldering the guard.
 
You heat the two parts to be joined , NOT the solder ! When the two parts are at temperature touch the solder to the parts .Proper dimensions of gap will , by capillary action and flux will cause the solder to flow just right !
 
We didn't get the blade up to the point of soldering the guard yesterday, so we will have to shoot that next weekend.
 
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