Do-it-yourself gear -- Zippers

I have several nice duffel bags with zippers that don't work. They are either going to get fixed or thrown out. That project is the "excuse" for digging into this and working up these notes.

Some quick notes about zipper maintenance are in order. First is that just washing a dirty zipper on a pack or duffel can get debris out of the zipper and get it working again. A tiny bit of silicone grease works wonders on a clean zipper that is hard to zip (but may attract dirt and grit). Sometimes a zipper than refused to zip up properly can be fixed by using a pair of pliers to tighten up the zipper pull. But sometimes it is just necessary to replace the zipper.

Types and brands of zippers

There are two basic types of zipper, coil (or continuous coil) zippers, which are what people are thinking of when they go looking for a YKK zipper, and zippers with individual teeth (sometimes called "stamped"). Stamped zippers can have metal teeth (like my blue jeans) which are stamped or crimped on the zipper tape or they can have plastic teeth which are molded onto the zipper tape. At this point, I can't say whether one or they other is better for heavy duty outdoor use. Look at your garment! I find both molded plastic and coil zippers, with molded plastic tending to predominate for use as the main zipper on a parka.

• Understanding zipper types and parts
• Video: Dutch - install zipper pulls on coil zipper
• Video: Sally Tomato - zippers by the yard
• Video: sewing a zippered bag

Another major distinction is between separating and closed bottom. If you are making a jacket, you will want a separating zipper, which has a tooth on one side and a "box" to receive the tooth on the other. This is something that we are all familiar with.

Zipper sizes and gauges

The number itself is the width in mm across the teeth with the zipper zipped closed.

Zipper sliders

So, let's get busy

I am going to use a #10 coil zipper to repair the bag. The old zipper looks like number 6 or 7. I have a couple of Patagonia "black hole" duffels and they both use #10 zippers and have been absolutely bulletproof.

I use two #10NL zipper sliders. These cost 85 cents each where I buy them, I need about a yard of zipper and the #10 zipper is $2.12 per yard. All told then, the materials to repair one of my duffels costs just under 4 dollars.

Step 1 is to rip out the old zipper. I turn the duffel inside out and get busy with a fairly new single edge razor blade. The old zipper has 2 lines of stitching. These are straightforward to cut out. The complication comes at each end of the zipper. At each end, a line of stitches both holds the bag together and serves as a zipper stop. This can be cut out with some extra care. The trick using a single edge razor blade is to cut only stitches and not damage fabric which is to be saved.

As part of removing the zipper, I also remove two layers of webbing that are part of the bulky seam at each end. This webbing made a short loop that held a plastic thing to attach a shoulder strap -- that I never did use. Trying to sew though all of that broke my needle, so it only makes sense to get rid of it.

Step 2 is to cut a piece of zipper from my 4 yard long stock piece. I cut it an extra inch long -- it can always be trimmed later, but if it is too short, I am screwed. It comes zipped together. I end up needing 34 to 38 inches, each bag is a little different.

XXX

Step 3 - sew the first side of the zipper. I turn the bag right side out since I want to sew fabric close to the edge of the zipper teeth and need to see what I am doing. With the zipper all zipped up, I pin the zipper to the side that will be "under the flap" when the bag is finished. I am using Guterman Tera 80 thread. I began with an 80/12 needle, but after I broke it, trying to sew through those two layers of webbing, I switched to a 90/14 needle, which handles this big thread better.

I sew this on, using my zipper foot, with a line of stitches close to the zipper teeth (but not too close). I add a second like of stitches about 1/4 inch back from the first.

Step 4 - sew the second size of the zipper. I turn the bag inside out again. I also decide to pull the slides off the zipper (after determining where this side of the zipper should be with the zipper zipped up. The position of the zipper relative to the other side (the flap) is determined by how I positioned the first side in step 4. At least that is true if I want it to lay flat, as I do.

With the slides off the zipper, it is straightforward to pin and sew the zipper with two lines of stitches once again.

Step 5 - put the slides back on and sew those seams at both ends. Care is needed when installing the slides so that stitching on both sides lines up and that there is not a big "bubble" of zipper on one side when you zip the bag closed. Once the slides are on, sewing the ends is simple, except that I work the machine by hand as I sew across the zipper teeth. I have to lift the foot and fish around to get the needle through the teeth. I use 3 lines of stitches and call it good.

How I screwed up the first time and what I learned