problems with casting aluminium handles

[Bart student]

Hello folks,


I tried casting some aluminium handles on some forged knives I made, and I ran into a few problems. so.. I'll line 'm up for you.

1. you ruins the temper of the blade the first two inch if you let it cool down slowly.

2. I could quench the alu as soon as it is nearly solid, but I fear a cold water quench will ruin the blades hardness again.

3. there are bubbles in the aluminium, I assume because I leave it to cool down slowly, as my theory is that a too soft temper is better then a too hard one.

4. I was thinking ablout rehardening the whole thing, but I guess I will ruin the handle that way.

Other then that, it works nice.. looks like soldered on, very solid and excellent for working knives. the way i like'm

Oh... I'm doing this in an open crucible (and I got only one !), in a charcoal forge. my form for casting is a thin plated steel pie which I hammer shut first on the bottom, and jam right next to the forge with the opening up. Then i put in the alu, then the knife, and I hold that till it feels solid. Then I left it in the dying forge, so the alu could cool down slowly, with the blade protected (which was already coloured by the heat).

If you could help me even on one question?problem, I would be very gratefull.

Greetz & thanks in advance.
Bart.

 

[Matt Shade]

Is there any possibility of suspending the blade in water?
Maybe you could get ahold of one of the old 5 gallon buckets thats made out of steel. If you fill it with water and put a peice of sheet metal over the top with a slot cut in it. You can suspend the blade in water with the tang sticking straight up. Fit the mold around the tang and pour in the aluminum. That leaves a little more shapng and finishing work around the top and the but of the handel, but should take the heat away from the blade. I'm not sure how you release the mold though. There has to be some way to make it work.

 

[peter nap]

I hate to admit I do this but...I wrap wet rags around the blade when I'm getting the tang really hot. You'd be suprised how cool it stays.

 

[Eric M Ericson]

I spent an hour writing out how to make plaster molds and pour safely. and how to keep the blade cool and hit the wrong button and it went away

start with the blade you want to haft. and form wax around the tang in the shape you want for a handle(if your wax is to hard at room temp. melt some vasilene into it) get 2 plastic bowls the same size and bigger than the handle. cut a notch in one long and shallow. fill the bowl with plaster and float the handle in it.

the edge of the blade is outside the bowl the plaster comes half way up the handle. the unground part below the edge is in the plaster the edge itself is sticking out. the top of the plaster should be wavy not smooth.

when this hardens spray it with PAM(release agent) cut the bottom out of the second bowl and tape it edge to edge with the first bowl. now pour the second bowl full of plaster. when they are hard remove your plastic bowls and tap the seam they should split apart(note I said should, not would).

Your mold is almost done. you have to cut a funnel shaped hole to let your metal in. choose either the back or the front of the mold. grind a flat area parallel to the blade but purpendicular(at right angles) to the line of fissure. cut a "V" groove from the center of the flat area to the largest part of the handle clamp the sides back together and open this up with a 5/16 drill bit. leaving a 5/16 hole at the handle area of the mold open the outside.shape the outer opening of the hole into a funnel big enough to pour into. now open the mold back up and scrape 2 small lines(one at the top and one at the bottom of the handle) across the mating surface of the mold handle to edge parallel to the the sprew but not conecting to it. these are gas vents and allow the air to escape when the metal goes in through the sprew.

now LET IT DRY !!!!!a couple of weeks in the sun and then bake it to be sure.
"sculptor's rule of thumb after you have baked it and are surtian it's dry and no wax or water remains, bake it again."
(be sure about the water content. wet plaster molds explode)

when you are sure it's dry find a low spot for your mold on the ground near the forge and build low earth walls around it.(probobly 4inches high by 4inghes thick is enough) If the metal spills or the mold breaks you want to be able to control it.

insert the blade into the mold and clamp it together.( I would use metal "C" clamps don't over tighten them) take wet rags and wrap them around the exposed blade(make sure they stay wet) set it sprew up inside your earth dam and you're ready.

melt your alluminium and pour away

By the way this also works with brass

 

[tom mayo]

DO NOT BREATHE THE FUMES !!!!!!!!!!!!!!!!!!

 

[Eric M Ericson]

I was talking to a frend who does casting and he recamends melting aluminumin a coffee can(don't use it more than once)and save your crucbal for brass and other things that require more heat.

bend a pour spout in the top of the can befor you start and hold it at arms length with a pair of long handled pliers.

it works well with small amounts

(don't try this with brass)