New crucibles (by alaric)
Just before the wedding, I got two crucibles. Proper A4 salamander crucibles, made from some refactory stuff, rather than stainless steel cups as I'd been using up to then.
However, the stainless steel cups are easy to lift - I punched holes in the sides near the top and put bolts through, so the thing could be lifted using barbeque tongs (the wire loops of the tongs slip over the bolts, securing the crucible). The salamander crucibles, being made of a clay-like stuff, cannot simply be drilled and fitted with lugs; the material wouldn't take the strain when at red heat.
So I had to make tongs. I picked up two 7mm square cross section iron rods from B&Q, a metre long each, and forged them into tongs by using the torch to take parts of them up to red heat, then banging them with a hammer on top of an old steel beer keg or bending by (heatproof gloved!) hand, until they had curved bits that cupped the bottom of the crucible, and met at the top with a hinge.
Well, getting the two bits the right shape for the crucible AND meeting up at the top was pretty tricky, and then we had trouble drilling through the things (using a high speed Dremel was a mistake that got the drill bits hot enough to destroy their hardening; had to use the Black & Decker to drill the holes slowly... although I only have a drill press for the Dremel. Luckily, the hole I'd made drestroying drill bits in the dremel acted as a started hole for the big hand drill). So the tongs are a bit... imperfect.
If I could weld, I could make proper ones or do what the other guys do, which is to make highly durable, large, stainless steel crucibles (as opposed to my little cups) out of thick-walled steel tubing. Not that I've ever found any thick-walled steel tubing lying around as they all seem to.
As it happens, it turns out I need a second person to use a hooked rod to make sure the crucible doesn't fall out of the tongs when I'm pouring... Ok, I don't want to do melts without another person in case I have an accident anyway, but it's wasteful to need two people to do the job of one.
Anyway, at least the things worked, enabling me to use my nice proper crucibles. It takes a long time to heat up the 1cm-thick walled clay crucible compared to my 2mm-thick steel cup, but once it's all glowing red hot, it sure melts stuff fast. What's more, it keeps the aluminium hot once I've lifted it from the furnace and while I'm pouring, enabling me to take it a bit easier in this delicate stage!
Metalworking | alaric | 
Sun 22nd Aug 2004 9:45 pm
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By Jon Greengrass, Fri 21st Sep 2007 @ 6:55 pm
Hi Alaric,
I have just started building my own foundry and have been searching the net for inof
When on page 1 of the search your site came up! I live in North East Scotland at the moment And getting hold of any type of proper refractory to line my furnace is not possibel so i so I have ground up cat litter to make bentonite and hope to mix it with sand.