My machine, a Husqvarna Optima 120, is over 25 years old. One day as I was showing my nephew how it worked, smoke started coming out of the right side. After a night in the back yard and a week with the mechanic back it came, good as new. The original kit of accessories was very basic, so far I've added a button hole foot, one for leather and the little attachment you see below. As a design student I worked on industrial models that did just one thing...straight stitch at break neck speed. Maybe that's why I like my old clunker, it does just a couple of things, it's simple to use, just the basics.
1. The very first thing you need to do before anything else is go and buy an invisible zipper foot for your machine. They are expensive but will make this process so much easier. The clear plastic version I selected allows me to see what's going on and It's also shorter so the needle position is closer to the front end which means I can stitch further. The grooves on the underside, to the left and right of the needle, are for the zipper teeth to move through.
2. For a regular zipper you sew the seam leaving an opening to stitch the zipper into. For an invisible zipper you sew in the zipper and then sew up the remainder of the seam afterwards. First press under the seam allowance on both sides toward the wrong side. The fold lines are very important, they help guide you as you sew in the zipper. If you need to neaten the edges do this first, I'm cheating and using the selvedge.
3. Lay out your fabric and zipper right sides up. This just helps you to orientate yourself....unzip.
4. Open out the seam allowance on the left hand side and place the zipper teeth of the left hand side of the invisible zipper next to the fold. The right side of the fabric and the right side of the zipper are now facing each other. The top of the zipper tape should be aligned with the top of the fabric, pin in place
5. Now it's getting exciting! Position the teeth on the left hand side of the invisible zipper so they sit directly underneath the left hand groove on the foot. Slowly start stitching and you'll notice the foot uncurls the zipper to allow the needle to stitch very close to the right of the teeth. Continue until you can stitch no further.
Continue until you can stitch no further.
6. Pin the right hand side of the zipper in place, right sides together. The teeth should sit next to the fold as before.
This time the zipper teeth on the right hand side of the zipper should sit directly underneath the groove on the right hand side of the foot. Start stitching and you'll notice once again that the foot uncurls the zipper so the needle can stitch very close to the left hand side of the teeth.
Stitch as close as you can to the end and making sure your zipper is open as far as it can be.
7. So the zipper is in but as you can see below the zipper the seam is still open. Change to a regular zipper foot.
With right sides together and with the zipper tape moved out of the way position the needle over the end of the stitching for the invisible zipper. The stitching should overlap a little. Starting slowly stitch the seam together, press and...
you're all done.