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Trying to make a table-mounted hot knife for rope cutting Answered

I'm wanting to build a mountable hot knife for cutting climbing rope, similar to the ones at http://www.wirecare.com/hot-knives.asp and  http://www.rocknrescue.com/acatalog/Table-Hot-Knife.html, using a method similar to flywoodkb's https://www.instructables.com/id/Hot-wire-foam-cutter/. How should I go about keeping the "prongs" coming out of the box from electrocuting me/causing a short? I'm hoping to use a jigsaw blade for the blade part.Also, I have a handful of transformers from disassembling some electronics. Is there a way to tell what voltage and amperage they are?  Any help would be appreciated. Thanks!

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Goodhart
Goodhart

9 years ago

Higher amperage transformers (most are very pricey) would be best; and using an "element" (high resistant, like an electric stove) except it'd need to be straight. I assume nichrome wire is too thin?

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The Insomniac
The Insomniac

Reply 9 years ago

What's nichrome wire? I was considering using this thing: http://imgur.com/a/GNPDg from an electricd griddle, but I couldn't figure out where the electrodes would go to. Any ideas? I had thought the center spikey thingey was an element, but it didn't heat up when I plugged it in. Thanks!

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Goodhart
Goodhart

Reply 9 years ago

The "element" is inside the actual gridle, you just have "input" controls shown.   Nichrome wire is a high resistance wire that will glow bright red at the proper power input levels.   Often used in toasters soldering irons, and hot glue guns, etc. 

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The Insomniac
The Insomniac

Reply 9 years ago

Cool! Thanks for the info. I'll see what I can find that's salvageable at my local thrift store. Perhaps I might wrap some nichrome wire around the blade part.

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steveastrouk
steveastrouk

9 years ago

Get yourself one of the old classic Weller "Soldering guns", which looked like an electric drill, with two bars coming from the front, where a wire "tip" was connected between the bars.

Freak out the switch, so you can mount it remotely, make a "tip" the shape of the blade above and connect to the bars.

The voltage on the bars is <<1V.

Steve

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Mrballeng
Mrballeng

9 years ago

What if you just mounted two soldering irons in a platform and connected the two with a long razer blade or even some wire?

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The Insomniac
The Insomniac

Reply 9 years ago

That would require two wires to plug it into, plus that's a bit expensive. Not to mention kind of ugly

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Mrballeng
Mrballeng

Reply 9 years ago

I was actually thinking about making one myself. I think I could hack two together for about $5. I'll let you know how it turns out.