May 27, 2020

Hot knife for cutting fabric

My hot knife
I have thought for some time that it would be nice to have a hot knife to cut fabric. It took me all of 5 minutes to make one, as you see above. You can also see the original soldering tip I replaced with the copper wire I formed into shape.

I was inspired by the following videos. The last shows a commercial hot knife being used to cut the material for a zippered bag.

It should be obvious that a hot knife only works on synthetic fabrics (nylon or polyester), not on cotton.

The idea with a hot knife is that the knife cuts the fabric and melts the edges all in one operation. You can buy a hot knife for $150 or so.

I had an electric soldering gun laying around that I essentially never use. I bought it for a few dollars at an estate sale store. So, as of today it is repurposed as a hot knife.

It cuts through parachute cord nicely as well as fabric!

I pulled a chunk of 12 gauge copper wire out of my box with household wiring supplies and cut off a length that seemed about right. I probably used about 8 inches of wire. I quickly bent it to a shape I liked. Then I took it to my vise, and using the vise as an anvil, pounded the business end of the wire flat with a ball peen hammer. It flattened nicely and left a bit of a rounded edge. I could use a file or sandpaper to thin that edge somewhat, but I'm not sure that is necessary or desirable. Once this was done, I slipped the nuts on, then bent two short right angles on the end of the wires.

It heats up in seconds and works well.

Have any comments? Questions? Drop me a line!

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