View Full Version : Hot knife help please
04-12-2002, 03:42 PM
Help please, I'm trying to begin my jabba's palace diorama and have amassed a huge store of styrene foam to make all the complicated curves from but I need assistance in making a hotknife to cut the stuff with so that i don't end up with tiny styrene balls flying all over the place.
I know it involves a large batteryand lengths of wire and some kind of insulated handle but how to actually put one together eludes me. if anyone can help with the simple info it would be greatly appreciated. thanks. :)
Its been a while since I made one but from memory I think you need a 12v battery, some 0.5mm wire to act as the 'blade', insulated wire with crocodile clips on each end x2, some nails and three pieces of wood to make the handle.
Assemble the three pieces of wood in a C shape and fix them together. Nails need to be inserted on the end of each of the 'prongs' and two thrids of the way along the prongs.
You then need to attach the 0.5mm wire. Starting at one of the nails two thirds of the way along a prong wrap it round the nail to give a secure starting point. Then stretch it to the nailat the end of the same prong, wrapping it round to make it secure. The wire then needs to be stretched across the gap to the next nail securing it to that nail, finishing at the fourth nail.
Next attach one of the wires with crocodile clips at each end to the battery and the other to the wire on the prong. Repeat to complete the circuit. You can now slide the clips up and down the wire on the prongs to increase or decrease the resistance (thus making the cutting wire hotter or cooler). Moving the clips towards the end of the prong makes the wire hotter, while moving them away from the ends makes the wire cooler.
A couple of tips when cutting. The wire should not glow red as it will quickly snap, it should be hot but glowing. The cut the wire makes should only be a bit wider than the wire itself. Also make sure you do it in a well ventilated area as when burnt it gives off carcerngenic fumes (not nice).
I've attached a rough picture to clear it up a bit, give us a shout if you've got any further questions. :)
04-14-2002, 06:09 PM
COOL! Thank you so much for that. I had an idea about it but like you, it's so long since i saw one used I just didn't want to risk attempting it in case i started a fire or something daft. I'm not teribly technical so My DIY mad partner can get to work making me one. This is so cool. I'm assuming that the wire at the end that stretches across can be made into a curve too so that you can cut arch shapes? It's just that some of those arches in Jabba's palace are quite tricky. Hmmm. make the hotknife big enough to do the larger curves Jargo, course you do.
Sorry I answered my own question while typing. :) I know what to do now. Thanks again for this. I'll let you know how I get on.
Hey, no worries, just don't go pluggin it in to the mains. Though the wire explodes nicely if you do that:evil:
Oh the other bit of adviceis if you plan to use spay paint make sure it is polystyrene friendly otherwise it melts, I found out the hard way. Oh well it was only two hours work down the drain.:frus:
04-16-2002, 07:59 PM
HAHAHA! :D know what you mean. the best thing to do with polystyrene is to cover it with tissue paper using PVA glue. It protects the foam and provides a good base for the paint to cling to at the same time.
My partner looked skyward when I handed the diagram over. :D looks like it'll be a build several sizes to do the job properly. some of those walls are really long. Anyway, thanks again. :)
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