I bought a hoodie made from interlock recently and decided to alter it for myself. But my machine only has a standard presser foot, and the knit keeps bunching up and skipping stitches. Are there any tricks to this, or do I really need a special foot?
The main thing is don't pull the fabric and don't use high thread tension, otherwise the knit will stretch even more and get loopy. A lot of beginners think you need to increase tension, but that only makes things worse. Also don't use a needle for thin fabrics - for interlock you need a medium-thickness needle, ideally a special one for knits (Universal or Stretch), but if you don't have that, a regular size 90 needle works fine too, as long as it's new and not dull.
You can work with a standard presser foot if you change your stitch. Try a zigzag instead of a straight stitch - it gives the fabric a bit more freedom and doesn't bunch it up as much. Or look through your machine's menu for some kind of elastic stitch for knits, if it has one. Lower the needle smoothly, not with a jerk. It also helps to put thin paper under the seam (tracing paper or even toilet paper) - it holds the fabric in place and then peels off easily afterward.
If you're going to work with knits a lot, a presser foot for stretch fabrics really isn't expensive and honestly makes life easier - it doesn't press down on the fabric so hard. But for one hoodie these methods should do the trick. The key is don't rush, go slower than normal, and don't try to force-feed the fabric through the machine.
Try this too - use a ballpoint needle for knit fabrics (has a ball at the tip instead of a sharp point). a regular needle just pierces the fibers and tears them, which is why the thread loops. a ballpoint needle pushes the fibers apart more gently, so you'll get way fewer loops. they're dirt cheap and the difference is huge.
another important thing - gently pull the fabric slightly behind the presser foot (after the needle has gone in), but don't pull it toward you. just help it glide under the foot without resistance. and yeah, definitely lower the thread tension - knit fabrics usually need lighter tension than cotton.
if it's thick interlock, tear-away stabilizer might help (thin paper under the fabric, then you just rip it off afterward). but honestly, with a fresh needle and loosened tension it should work fine even on a regular presser foot.
When I was altering my things, I noticed that the problem is often not just the tension, but the stitch itself - on a regular machine it's better to use a zigzag instead of a straight stitch, it gives the fabric a little give and doesn't tear the fibers. I'll second the advice about using a ballpoint needle for knits - it really does help, but here's what people forget to mention: even with the right needle and loose tension, you can still get loops if you're sewing at high speed, especially on thick material like interlock. Slow down your machine, and half the problems go away on their own.
Honestly, a special presser foot really does help, but if you don't have one, pay attention to your sewing speed - a lot of people forget that at high speeds the machine just can't catch the stretch fabric evenly. Try sewing slower, you can even do it at half your normal speed. Jersey needs a more relaxed rhythm so the presser foot has time to feed the material smoothly.
Another thing people often miss: check whether your needle plate is clogged with lint and fuzz from the fabric. Interlock can shed badly while you're working, and if material builds up in there, the needle starts catching and causes skipped stitches. Clean the plate with a brush before you sew.
And one last thing - if nothing else is working, you can use a regular needle but one size smaller (like if you normally use a 90, go down to an 80). A thinner needle is less damaging to the fibers. It won't replace a special presser foot, but combined with low speed and proper tension it can really improve your results.
Interlock is dense knit fabric, and it's genuinely tough to work with on a regular machine. From what's already been suggested, the key things are a ballpoint needle for knits and a zigzag stitch instead of a straight stitch. But there's one more thing people often miss: try placing a thin water-soluble stabilizer or even regular tissue paper under the fabric. It supports the fibers from below and keeps them from bunching up when the needle pierces through. After sewing, the paper just tears off, and the stabilizer dissolves in water. Sounds weird, but it works.
Another tip from personal experience: before your main seam, stitch along the fabric edge right along the selvage, kind of like locking the fibers in place. The knit becomes a bit more manageable. And don't skip doing a test run on a scrap of the same hoodie fabric - fiddle with the tension, stitch length, and speed until you find what works best for your specific machine and this particular interlock. There's no universal setting; every machine is different.
A special presser foot would definitely make life easier, but if you don't have one, these three things - the needle, the zigzag, and the support underneath - give you results that are just as good.
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