I rarely buy new wires for my projects, since I rather recycle old cables that still lie around or those that are thrown away by others. I especially like to salvage multicore cables, such as power cables, old SCSI cables, or parallel and serial printer cables. The main problem doing this is to peel off the outer insulation shell of the cable which surrounds the inner wires which I want extract. It's possible to use a cutter knife to make a slit all along the full length of the cable, along which the inner wires can be pulled out sideways from the outer shell. But doing this manually is tedious and also dangerous, as the knife can easily slip off an hurt you - I know from experience :(

The aim of this project is to render the peeling of multicore cables more easy. For this, I made a little tool which guides the cable through a tight hole into which protrudes the tip of a cutter blade. Pulling the cable through the hole creates straight longitudinal cut of a precise given depth all along the cable.

My cable peeler tool consists of three parts:

• A disk with a set of guiding holes of different diameters which are circularly arranged, so that for a given cable thickness the disk can be rotated to the properly sized guiding hole. Two exchangeable disks are provided, one for small cable diameters (3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 and 8mm) and the other for larger diameters (8.5, 9, 10, 11, 12 and 13mm).

• A handle to which the disk is attached, so that the selected guiding hole is aligned with the tip of a standard 9mm cutter blade, which is safely contained in a recess on the side of the handle. The disk is hold by a central M4x20mm screw and a corresponding wing nut, while a notch on the handle which prevents the disk to rotate.

• A clamp to firmly hold the blade in place once it has been positioned for the desired cut depth. Two M3x8mm screws on the opposite side are tightened to pull the clamp onto the blade. A second spare blade is position under the screws, which makes sure that the tightened screws are not drilling into the plastic of the handle.

For "peeling" a given cable, look for the best fitting hole in one of the disk and mount that disk in the correct position. Then adjust the tip of the blade for the desired cut depth. Note that it is neither necessary nor desirable to cut through all of the insulation shell. Cutting half way through the insulation shell is enough and ensures that the inner wires are not damaged. Once you can get hold of the inner wires (may be cutting open manually the first 3-5cm) they can easily be torn sideways out of the shell, separating the remaining uncut part of the outer insulation.

The 3D-printing objects for the cable peeler tool are available as fully parametrized OpenScad source code and also as ready-to-print STL files. One STL file is provided that contains all the parts together, and additionally a separate STL file for each part is also provided to allow printing individual pieces.

The OpenScad source can of course be easily modified for special need, such as even larger cable diameters or specially formed (i.e. non round) cable cross sections.