Load a Bundle of Wires Into Split Loom in One Pass Using a Box Wrench

The Problem

Split loom — the corrugated plastic tubing with a slit down one side — is easy to put over a single cable and awkward over a bundle. Working a handful of wires in means holding the slit open with one hand, feeding wires with the other, and watching the ones you already placed spring back out behind you. On a long run you end up doing it in sections and the loom walks off the bundle as you go.

The slit itself is the other problem. The cut edges of the corrugation are thin and hard, and pushing wires past them repeatedly is how you score insulation, or your fingers.

The Technique

Use a closed-end wrench as a shuttle that holds the slit open and pulls everything through at once.

  1. Pick a box wrench whose ring is comfortably bigger than the finished bundle, and whose ring is thin enough to pass down the inside of the loom.
  2. Pass the wire bundle through the ring so the wires sit inside it.
  3. Feed the head of the wrench into the end of the loom and push it along, letting the handle ride out through the slit.
  4. Push the wrench the length of the run. The ring rides inside the tube, propping the slit open ahead of the wires, and the whole bundle follows it in — no wire ever gets pushed past a cut edge.
  5. Slide the wrench off the far end and let the loom close.
Pro tip: Size the ring to the bundle, not to the loom. A ring much larger than the wires lets them shift and spread inside it, which is what jams the head partway down the tube. Snug enough that the bundle stays gathered is what makes it slide.
Pro tip: The trick works because the wrench is rigid and smooth. Anything that shape does the same job — a large flat washer, a ring spanner, a shackle. What doesn't work is anything with a gap in the ring, because the wires escape through it exactly where the loom's slit is.
Safety note: Loom the wires with the circuit dead and disconnected. Dragging a bundle through a tube puts real tension on terminations, and a crimp that was merely adequate is the one that lets go.

Electrical, plumbing, and structural work may be regulated where you live — check local code before you start, and note that a permit may be required. More in our disclaimer.

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