I really heart coiled cords. I think coiling is a very elegant way of dealing with the problem of unsightly slack cables, and often I find myself wishing that this or that appliance had come with a coiled cord. Replacement cords that are factory-coiled can usually be purchased and installed (if necessary), but that may be an unnecessary expense because, with some simple tools, it is easy to coil a straight cord yourself.
- Pipe or other metal mandrel
- Heat gun
- Sink with sprayer (or other source of cooling water)
- Duct tape
- Aluminum foil
- Cord to be curled
Step 1: Wrap the cord around the mandrel
Find a metal round, the outer diameter of which is equal to the internal diameter of the coil you want to set. Duct-tape one end of the cord to one end of the mandrel, as shown, and then wind the cord itself tightly around the mandrel until all the slack is taken up. Then duct-tape the other end of the cord. Make sure to use plenty of tape so the coil doesn’t come loose with handling.
Step 2: Protect the ends of the cord with foil
If your cord has a connector at either end, you have to be careful not to melt, warp, or otherwise damage it in the process of setting the coil. So cover the taped ends of the cord with aluminum foil, reflective side out. This will help to reflect heat from the heat gun away from those places you don’t want it to go.
Step 3: Apply heat to the cord
My workshop sink proved to be a convenient place to heat the cord. I set the mandrel across the sink, as shown, and rolled it back and forth with my left hand (to distribute the heat evenly) while waving the heat gun with my right. If you don’t have a sink or your coil is too long for one, you may have to improvise some other arrangement for rotating the mandrel while simultaneously applying heat.
Step 4: Quench the hot cord
Apply heat gradually, over the course of about ten minutes, until the plastic insulation just begins to smoke. Then immediately remove the heat and quench the hot cord with cold water. Continue cooling until the cord is barely warm to the touch. Remove the cord from the mandrel and blow-dry it completely with the heat gun on a low setting.
Step 5: Test the cord before use
Do not attempt to use the coiled cord until you have verified with a multimeter that it is not shorted or otherwise damaged. Using the continuity/ohmmeter setting, apply the probes to corresponding leads or contacts at each end of the cord. The circuit should close for corresponding leads, but should open when you move one probe to the other lead.
Notes and ideas
Be sure to work in a ventilated area. If you do this correctly, the plastic will smoke only for a moment, but it’s good form to avoid exposing yourself to that smoke in any case.
Instead of rotating the pipe as you apply heat, it might be possible to direct the air from the heat gun down the length of the mandrel (assuming it’s hollow) from one end, perhaps using a metal funnel to help channel the hot air. This operation should heat the circumference of the pipe, and thus the cord, more-or-less-evenly.
If the tape leaves behind residue on the cord, use a paper towel moistened with a dab of acetone to remove it.
Finally, I should point out that I have only attempted this operation on the guitar cord shown, which I think is insulated with PVC. It the insulation of your cord is some other type of plastic, it may or may not work for you. If anyone knows anything about plastics commonly used to insulate appliance and audio cords, please feel free to enlighten us in the comments.
Update: Timothy Silverman sent in this photo showing a cross-section of a factory-coiled cord. Note the “filler” between the wires and the sheath–it’s this material that supports the factory cord’s tighter coil. My cord has never been as “tight” as a cord with an original coil, but I’ve been using it weekly now for almost 8 months and it has not slackened appreciably.