Can someone out there tell me an easy way to make a hotwire cutter. Oh ya and not get myself killed while using it. I’m only going to be using it like one or two times. I’m in the Santa Cruz area so if someone has one that they would let me use, that would be great also.
Do you know the old style saws used centuries ago? Basically a sawblade attatched between one end of a wooden H shape. On the other end of the H there are a thightening mechanism consisting of a threaded rod and some wingnut bolts. Now, replace the saw with a hotwire and you’re set. regards, Håvard
That part is no problem. What do I use for heating the wire. AC, or DC? Do I just use a car battery? I’m not a sparky at all. I can build the saw but what size wire?
the size wire you use ( and use Nichrome witre, not just any wire) depends on the size of the power source. If there’s too much power, the wire melts and if there’s too little it doesn’t heat up enough. A train transformer or doorbell transformer works ok. A variac power source, where the power output is controllable, is ideal. My own setup uses a 3 amp doorbell transformer and about 16" of 20 gauge nichrome wire, though I’d maybe go with slightly smaller wire the next time. hope that helps doc…
tk,DOC that helps loads.
find the guy in your hood that is into model trains beat him up and take his controller then you can control how hot that wire will get. 
We will be selling variacs very soon. Like in a couple weeks. We will also be selling plans to make a harp and rocker templates. The “how to” is already in the archives but if anyone wants a copy, I have it. I am also compling a list of blank manufacterers which I will post here. Please e-mail me if you want to be on the list.
de nada - check your friendly neighborhood model airplane place, or somebody that supplies radio controlled model stuff - they carry nichrome for hot-wire cutting the model plane wings from foam. They might also have power supplies ( and more information on matching wire sizes to power supplies) , or someplace that sells electronic surplus. hope that’s of use. doc…
One of these days, when I have time, I’ll post pix of my crude setup. Anyway, here is how I made a simple but effective setup. Take a piece of 3/4 inch plywood and cut a big U with about 26 inch clearance across and 12 inches deep. Screw two eyebolts into each side of the wide opening in the loom. Attach 30 gauge NiCr wire to each eyebolt. Then, take an old extension cord, lop off the female end, strip the insultaion a few feet, strip the ends about one inch, and attach the black wire to one eyebolt and the white wire to the other. In the middle of the extension cord, wire a light bulb socket with a 200 watt light bulb. Make your cross section templates out of thin plywood or door skins, plug in, and you should be cutting slowly but smoothly. If you use another gauge wire then adjust your resistance accordingly (increase or decrease the wattage of light bulbs. You can always wire more bulbs in series to add resistance netting a hotter wire. To do the stringer cut, I use a saw with a fine tooth pull saw and then run each side through a woodworking jointer to make a perfectly smooth and perpendicular cut. However, you could just saw and make a pass on each side with your planer. Cheers, Gary Geist
My 24V/1.6A trafo does heat an 80cm long 0.3mm wire. My 12V/15A trafo does heat the same wire but only about 30cm long. Your car battery should work…it outputs about 40A I guess? start with a longer wire…make it shorte until it has the right heat. If it gets too short then you have to little V.
I’ve used a normal cheap 12V car battery charger made by Bosch. High setting cuts very rapid, low very slow. My wire is about 80 cm. One more thing, put a switch on the cutter so you can cut the power without having to pull out a plug or something. Saves you a bit of trouble. regards, Håvard
The battery or DC power supply seems like a better idea to me. 60 cycle AC current does not mix well with the human heart rate.
bagman, for your kind of use, I would definately go with Lucky Lab’s method. I did the same exact thing, but with a PVC frame instead of plywood and I used twisted rope to create tension on the wire.
I’d definitely go with the bowframe if I were you. It’s simple and proven by now. As for wire, Stainless steel works great too. You can get it from most places that cater to ocean fishermen (and women…). I would go with AC, and take a doorbell transformer as described above to knock it down to a less lethal voltage… Buy a dimmer switch at Walmart and place it in the low voltage side. It will provide you with temperature control
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thank you verry much