Finishing edges with a zigzag, since I don't do sergers
Okay. Last lesson we took a shirt in and shortened some sleeves, which means you've got raw edges now. Cut fabric, no finish on it. That's today's problem.
Here's the thing I have to say up front. I don't own a serger. I've thought about it, decided it's one more machine to clean and oil and store, and my zigzag stitch does most of what I need. If you've been watching videos of people running their fabric through a serger and feeling behind, stop. You're not behind. You've got a different tool that does a similar job slightly slower.
What a zigzag is actually doing
A straight stitch holds two pieces of fabric together. A zigzag stitch, run along a raw edge, wraps thread back and forth over that edge so it can't unravel. Knit fabric, woven fabric, doesn't matter much, though wovens fray worse than knits so they need this more.
Cotton, especially cheaper cotton, will fray in the wash if you leave the edge raw. You'll pull a shirt out of the dryer a few months from now and the hem's a fringe. This is the fix.
Setting up your machine
Most machines have a zigzag stitch built in, usually a dial or a menu option that looks like a little sideways W. You want:
- Stitch width around 4 to 5mm to start. Wider zigzag, more coverage on the edge.
- Stitch length shorter than your regular straight stitch, maybe 2 to 2.5mm. Too long and the zigzag looks sparse and won't actually catch the fray.
- Regular presser foot is fine. You don't need a special foot for this, though if your machine came with an overcast foot, that little guide with the wire on it, it does help keep the edge from curling under while you sew. Not required.
Test on a scrap first. Always test on a scrap first, this is not me being cautious for no reason, this is because zigzag settings vary wildly between machines and I've seen a stitch look perfect on one machine and look like a mangled knot on the one next to it. The machine's telling you something before you even get to your real fabric. Listen to the test piece.
Actually doing it
- Line up the raw edge so it runs just inside the right edge of your presser foot. You want the needle's widest swing to just clear the edge of the fabric on the outside stroke, not sew off into open air.
- Sew slow. Slower than you think you need to. A zigzag at speed on an edge that's curling or fraying already will bunch up on you fast.
- Keep the fabric flat, don't pull it through. Let the feed dogs do the work. If you pull, you'll get a wavy, puckered edge, especially on knits, which stretch if you so much as look at them wrong.
- When you get to a corner or you're finishing a loop, overlap your stitching by about half an inch instead of butting the ends together. Cleaner, and it won't pop open.
An opinion, since we're here
Everybody backstitches like it's the law. Lock stitch at the start, lock stitch at the end, tie it off like you're closing a parachute. For a stress point, a pocket corner, a strap, sure, backstitch it. For finishing a hem edge on a shirt you're upcycling for casual wear, a couple forward stitches and a knot is fine. I know that's not what the tutorials say. I've read the tutorials. This is casual clothing, not a load-bearing seam.
A note on knits
If you're finishing an edge on a knit shirt, go slower than you think and don't stretch it as you feed it through. Knits are the fabric that humbles people, not denim, whatever anyone tells you. A zigzag on a stretchy edge that's been pulled taut while you sewed it will look fine off the machine and pucker the second it's washed and stretched back to its resting shape.
I did a hike up Provo Canyon a while back, tracked the mileage like I always do, and came back and sewed a whole batch of finished hems that night without a single hitch. I've got no proof this is related. I just know I'm calmer at the machine on days I've moved my body first, and fidgety hands are how you get a zigzag that wanders off the edge of the fabric. Take that for what it's worth, which is not much, scientifically. I still believe it.
When it goes wrong
If your zigzag is bunching thread underneath, that's a tension issue, go back to your notebook, or start one if you don't have one yet, and note the fabric and the setting that worked. If the stitch is skipping, change your needle. I say this every module and I'll keep saying it because nobody believes me until they do it and the skipping stops.
Before next time: finish the raw edges on that shirt you shortened last lesson, and if you've got a scrap of knit fabric lying around, run a test zigzag on it so you've felt the difference from denim before we need it.