How do I adjust the bobbin tension on my sewing machine?
I'm trying to finish up Christmas gifts for my nieces and nephews, and today my sewing machine has gone wacko. I've been doing cross-hatch quilting and sewing with both straight and decorative stitches through multiple layers of fabric and batting (Warm-and-Natural, which is pretty thin). Suddenly, the bobbin thread isn't grabbing the front to make for a zig-zag pattern, and even with a straight stitch, the back is loose and knotted looking. I think this means the bobbin tension somehow got thrown out of whack, which makes sense because it started after I replaced the bobbin after refilling it with thread. Help!!!
STOP! Don't mess with the bobbin tension yet!
What you're describing is usually the result of threading with the presser foot down, so the top thread can't enter the tension, or not putting the presser foot down when you're sewing (easy to forget when you're working on a thick quilt) or you've got lint or something stuck in the upper tension.
Loops on the bottom are a sign that the top tension isn't getting enough tension. Loops on top are a bobbin tension issue.
Chances are you've got a misthreading issue. (And if you've had more than 4 hours of needle up and down time in quilting, it's probably time for a new needle anyhow. Soooo....
1) Stop, and give the machine a new needle and a quick clean and oil.
Take all the thread off of/out of the machine. It's faster to rethread than looking for a minor threading error.
2) Clean the top tension -- dampen a piece of much-washed muslin (a bandanna or pillowcase hem is perfect) with rubbing alcohol or unflavored vodka. Raise the presser foot and floss the upper tension with your damp muslin. Drop the presser foot while you've got a clean piece of the muslin between the disks and slide the muslin just one way. Raise the presser foot. (If you don't have rubbing alcohol or vodka around, use the newest, crispest bill (currency) you have in your wallet. Fold it in half lengthwise, put it between the open tension disks, then lower the foot and pull the bill through. The paper they use for paper money is very strong and the ink is mildlly abrasive and does a pretty good job of cleaning tensions.)
3) With manual in hand, rethread. If you've been messing with the upper tension, set it to 4, then try on scraps, adjusting till you get the stitch you like.
There's one other possibility... if you're using very heavy thread and a very fine needle, the thread can jam in the long groove of the needle, and not get pulled up when the needle rises. This jammed needle also gives the loops on the bottom effect.
I've also seen a badly dinged up sewing hook give this sort of problem, so you may want to examine it, particularly if you've recently broken a needle or jammed a pin while sewing. Dings can be gently polished out with crocus cloth.
It's really really rare to have to adjust bobbin tension in most machines, unless you're doing some specialty work like bobbin work (upside down embroidery). If you do have to adjust the bobbin tension, here's a good article: http://www.threadsmagazine.com/item/4302/understanding-thread-tension
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