How to attach a guard ?

R

ritsmon

Joined
Jan 2, 2011
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i would like to know what kind of solder and flux you use to attact a stainless steel guard to a carbon steel knife blade.i have tried useing silver solder and silver flux but all it does is gum up and not take the solder like brass does.
 
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4% silver-bearing solder and Stay Clean flux. The metals have to be clean. The sooner you solder the guard after cleaning the joint to bright metal the better.
 
I have used JB weld a number of times, on my bike and car, not on knives, and i need to mention something. Unless i am doing something terribly wrong, I have been using JB weld for auto mechanic work for a number of years, i don't recommend using it. i have had instances where Jb weld worked ok, but all in all, most of the time I use it, it only lasts for so long. And again, i have never used it on knives, but I never plan to. Especially in small amounts, like a small bit inside a guard on a knife, i have to say it is a big gamble. I know many guys here swear by it, but again, it is relatively easy to use, as long as you prep the parts you are Jb welding, before you do it. Well, I do, and give it plenty of wait time, and i still see it fail on things with barely any pressure, after about a year, give or take. Please, again, maybe there IS something I am doing wrong, but I seriously doubt it. I have used the kind in the bar, that you just press mix together untill it turns from black and white, to grey. And, i currently have 2 large tubes of the 2 part JB weld, that is harder to find, at least by me. And, I really hope not to make anyone feel like they shouldn't have used it on say a knife, but from my experience working on my own car and bike, being able to see my projects long after I use something like this(unlike a knife that may go on a display or something), leads me to never really use it again, except maybe a quick fix emergency temporarily, and again Ive seen this happen on parts that didn't even need to hold pressure, or anything crazy. Just my honest opinion, I hope to help with my advice if i can, when i can. thanks

dave
 
Welcome to the Bldeforums.
Filling out your profile will help us help you.

JB weld is used as a sealant when used to install tight fitting guards. I would not recommend it for bolsters or any other knife use.

Soldering of guards and bolsters is a skill that many knife makers never get right. The flux and solder need to be of the low temperature variety that has tin and a little silver in it. The brands used are things like Stay-Brite, TIX,etc.
The flux is usually sold with the solder as a matching product. I like to use the pink thicker flux. I feel it works better than the clear thin stuff.

The trick to getting the solder to flow is heat control and cleanliness. If there is any dirt or oil on the surface, the solder will not flow. If the surface gets overheated ( above about 550F) the flux will turn dark and get gummy, and the solder will not flow.

Here is a short soldering tutorial:
File and sand everything so it meets flush. Solder doesn't like to fill spaces.
Clean everything and wash well with soap and water. Don't touch the surfaces with your fingers if you can help it once clean and dry.
Heat the metal near the joint, but try and avoid directly heating the joint itself. The solder will flow from the point it melts toward the heat source, so the heat should be applied to the other side from where the solder is placed.
Flux the joint well, and slowly heat the entire assembly. If one spot is hot ,and the rest isn't as hot, it will only pool up in the hot spot. Place a 1/4" piece of solder on the joint, and add a little more flux....Only a little. As the joint gets up to temperature, the solder will start to melt, If everything is right, it will flow into the joint, if it doesn't and starts to rise up as a bead, apply a little more flux, while keeping the joint at the right temperature. This is where most folks go wrong, as they try and apply more heat to the joint. More heat will stop the process dead in its tracks, by burning the flux. Add more solder by touching the solder wire to the joint as needed. If there is a stubborn spot that the solder does not want to flow along, use a piece of brass rod with a point on it as a soldering tool, and scrape the tip along the joint. The solder will usually follow the brass tip nicely. Re-flux if needed, but only use a bit at a time.

The heat source is important - use a small soft flame. A jewelers torch is great, but a small butane torch will work well. A propane plumbing torch is way too big and must be carefully used with skill. A heat gun works very well. Many folks are afraid to apply the heat to the blade, feeling they will ruin the temper. If the flame is properly applied, the temper will be fine....just go slow and apply the heat evenly to raise the whole blade and bolster/guard assembly up together. Wrapping the blade in a damp cloth, or clamping it in a vise while soldering will keep the heat to the ricasso area. Just allow enough metal to be exposed to keep the joint at 450-500F.
I like to clamp the tang end in the vise, and have the blade sticking upward. I apply the heat from the tang side of the guard/bolsters, and apply the solder from the ricasso side. If I overheat the tang a bit, there is no problem .

Once the joint is made, don't touch or move the knife for at least five minutes. The solder needs to cool and crystallize without being disturbed or cooled too fast. After it is solidified and crystallized, wash the knife well to remove all flux residue, and use a bench knife to trim any excess solder off the sides and tang area. At the ricasso joint, use a scraping chisel made from brass or bronze...but not a steel blade or scraper, as the steel blade may scratch or gouge your knife blade. Sand away any excess solder and shape the guard/bolsters as needed. Avoid getting soldered pieces too hot when shaping, as it can quickly get 400+ degrees and melt the solder joint.
 
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