Can silver be cast onto a knife tang?

[Purple Bullet]

My granddaughter wants a knife. Not just any knife. She wants a serpentine blade dagger in feather cable damascus. I have some old silver spoons that I'd like to use on the guard and a bolster near the pommel. I plan to use some horn scales.

I typically braze a guard in place before heat treating. I braze a length of 1/4" brazing rod on either side, smash them together where they extend past the blade, braze/weld the pieces together then grind and polish as needed. I know silver CAN be brazed, but I've never done it. 

I was thinking of making a model of wax on the blade, packing tight in green sand (Mississippi River sand is very fine grain down here) melting out the wax and pouring in the silver.  I drilled a couple of holes through the tang where the silver will go to make solid mechanical connection. However, being buried in sand I would not be able to preheat the steel very much. I'm afraid that the different coefficients of expansion might be a problem.

Anyone ever try this?

[Frosty]

Tin the knife where the guard and bolster go with low melt silver solder and do what you describe above. Put a chill stop on the blade just beyond the guard so it doesn't run the temper out of the blade.

Remember to put a heat stop on the blade when you tin it, low melt silver solder doesn't require a lot of heat but it's enough to foul a blade's heat treat. Wrapping it with wet rags should work but if you have copper bar and a C clamp you're golden. Do the same when you pour the silver but make sure the wax is clear first. A little silver soldering flux when you pour won't hurt.

Frosty The Lucky.

[Purple Bullet]

Thanks Frosty. That makes sense. I was planning on quenching and tempering AFTER I get the guard on. I figure it would be easier to temperature protect the guard than the blade, although I'm sure that would work too. 

I just got the ceramic crucibles and tongs in today.

[Frosty]

If you heat treat afterwards use a higher melt silver solder, something just below the melting temp of the spoons. Keeping the silver from melting shouldn't be difficult.

Frosty The Lucky.

[BillyBones]

I do not know if this is relevant or not but when i was working in a tattoo shop we made our own needles. (we had an autoclave and sterile packaging so no it was not some back room shady stuff) The needles were attached to the bars with silver solder, you dont want to use lead based around an open wound. To get them to stick they must be absolutely as clean as you can get them. Anyway just wanted to say clean, clean, clean and when you think they are clean, clean them one more time. 

[Buzzkill]

A few years ago I did something similar, but with aluminum.  I had a hidden tang and cast the entire handle in place on the knife. Although it was a general success I've never done it again since that time, and I'm not even sure I can recommend it.    I used the lost foam technique in a bucket of sand.  Lost wax would probably produce a better handle. I had cut a slit in the bottom of the bucket for the blade to pass through and set the bucket on a container of water so that the blade was submerged while the handle was cast in place.  Although the thermal expansion coefficient is quite a bit different between steel and aluminum this did not seem to cause any problems with gaps or anything loose between the tang and the handle.

Admittedly, my way of doing things was probably not the best way, nor the safest, but it did work.  The potential for injury is very high if a small amount of water gets into molten metal.  If a small amount of molten metal gets into a large amount of water it's not as much of an issue, but I was flirting with disaster with that setup.  I just want to be clear that I am not suggesting anyone else try to replicate what I did.  There are other ways to protect the temper of the blade that aren't as dangerous.

Most of the guards I make now are stainless and I affix them after heat treating with a low temperature solder. Heating from the tang side and the use of a heat sink on the blade side does a good job of protecting the temper.  Like Billy indicated, "clean, clean, and clean." For me stainless is harder to solder than carbon steel or brass.  I think silver should be similar to brass as far as the ease of getting a good bond between the metals.

[Steve Sells]

I suggest you H/T the blade first, as I dont think you will have any success H/T the blade After you cast the handle

[Purple Bullet]

Well, it didn't work out. Frosty's advice was good and I'm sure the rest is as well. Where the silver flowed it stuck fast to the tang. My problem was the geometry of what I was trying to cast in green sand. I packed the blade with the wax guard and bolster into a bucket with the green sand. I left just a tip exposed of the guard and bolster. I then tilted the bucket on its side and used a MAPP torch to melt the wax out. It looked like a lot of wax went into the sand but I figured that wouldn't hurt. The silver hardened up before it flowed all the way around the blade and plugged the pour hole.

I may just go back to brazing a brass guard or try brazing silver. I probably should try again, though, leaving one entire side exposed. I was trying to pour with the plane of the tang vertical. Maybe I should try it flat. That would guarantee a large enough pour area although I may lose a bit more silver in shaping.

Steve - I use oxy-acetylene to edge quench and a toaster oven to temper. If I wrap the silver guard in wet rags for the quench I'm hoping to keep the guard below the melting point of silver solder.

I'll have to get back to this later. Right now I'm trying to make a bouquet of a half dozen Russian roses for our 51st wedding anniversary. When I do, I'll let y'all know. Thanks for the help.

[Frosty]

It sounds like you need to skip to investment casting, I don't know what kind of silver you're using other than old silverware IIRC. The melting temp will be lower than the 1,760f or so says my dented memory but it's close. Sand casting would probably chill a small melt, especially if it has to heat the tang.

If you use an investment, one of our IFI casters will have to tell about what kind of plaster and aggregate to use. It'll be easy to melt the wax out if you don't make the investment too thick. I suggest a large sprue and riser so the silver has plenty of weight to force it to all parts of the mold, a large riser also provides plenty of silver to allow for shrinkage.

Pouring the way you just did will work a treat, just use a smallish can say 2lb. coffee can size so once the wax is melted you can do a brief burnout with a Bernzomatic torch, the water bath below will prevent damaging the heat treatment and the tang will warm up. Pour when the investment is red hot and it should all stick. A high melt silver solder should work fine, if not the silver should alloy with it as it melts it out of the way and still stick. 

I got this last to work with wheel weight lead in copper plumbing caps, making copper boppers for flint knapping.

That is NOT the thoughts of a fine metals caster but I've tinkered a bit. I'm sure an experienced caster will speak up and correct me or reveal the secrets of the craft. We won't tell on you. . . Honest!

Frosty The Lucky.