The cord curled in my original project, before reversing. Note right-hand helicity, 19 turns.

Same cord, after reversing the coil. Note left-hand helicity, 21 turns.

One of the first projects I ever wrote for MAKE was about setting a coil in a factory-straight electrical cable or cord using a heat gun and a metal form. A recent comment on that project hipped me to this short video segment from the Science Channel’s awesome show How It’s Made:

In it, a technician in a factory that makes coiled retractable cables demonstrates a second step in the process that I didn’t know about when I wrote my original guide: after the initial “perm,” the coil is reversed by a machine that grabs both ends and twists it in the direction opposite the thermoformed helix. The industrial machine is apparently a bit of a trade secret, but the trick can be performed on a one-off basis using a bench vise and a hand drill.

Besides being a lot of fun to watch, I can now report that this process is a lot of fun to do. And works essentially as advertised on home-curled cords. The “inside out” cord, which started as a regular straight instrument patch cable, is now considerably tighter than before.

Thanks to Bart Patrzalek for the tip, and Brian Adams for linking to the instructive video segment.

Make: Projects — Cord Curling Part 2 – Reversing the Coil