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COIL ZIP 1 - Coils not meshing behind a closing slider

This is the most common coil zip problem. Either the slider has become distorted or it is badly worn inside. Internal wear is accelerated by dirt and grit contamination in the zip coils. Keeping zips clean and well lubricated also reduces the pull force needed to operate them.

Coil zip sliders are made from diecast magnesium, finished by nickel plating or painting. Pulling hard on a jammed or poorly running slider can distort the diecast slider body at the front connection ‘bridge’ between the upper and lower plates. The result is an increased gap between the plates at the back end of the slider. The coils on each side of the zip are no longer forced to mesh together. In the case of a badly worn slider it will usually need to be replaced. Try closing the gap first as old sliders are often slightly distorted as well.

The back-end gap can be closed down to the correct size by carefully tapping on the upper part of the slider, just at the back end, while resting the lower part on a firm surface.

The best way to do this is, so the force is applied only on the upper plate of the slider and not to the arm that attaches the puller tab or cord, is to use a small block of wood into which a slot has been filed or cut so it fits clear over the arm. If the slider has these arms on both sides (a double-pull slider, common on tents) you will need a second, slotted block to support the lower side. Work on a firm surface. If you have a vise available hold the lower block in that, or make the lower block large enough that it rests easily on a firm surface.

Before you start to tap the slider closed run it as far as possible along the zip to what would normally be the fully open end stop. That way, once it is operating correctly again it will close the full length of the zip and you won’t be forced to drag it back along un-meshed coils, possibly causing further distortion.

Lightly tap the slider closed using a small hammer. Start with weak blows and check the zip operation after each one. If there was no change increase the force of the blow a little. The gap difference between a working slider and one that doesn’t is a fraction of a millimetre. Hitting too hard will over-close the gap, resulting in a badly dragging slider. If you do that find a screw driver that will just fit under the back edge of the upper plate then twist it just a little to pry the plates apart.

A dry silicon lubricant is very beneficial in easing operation and prolonging zip life. These spray lubricants are readily available. Go to the net if your local outdoor retailer doesn’t keep stock.


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