Mitch's mom

I have changed the needle, rethreaded, checked my bobbin, made sure the needle is inserted correctly, and adjusted the presser foot pressure. It will stitch about 15 stitches then skip 1 stitch. I can hear it when it skips. Any ideas?

Candace

Check the timing and watch the hook while it's missing stitches.

J Miller

Besides doing what Candace said, try a completely different bobbin. The fact that it skips the stitch consistently every 15 stitches or so tells me it's not the hook or the timing. The hook is a rotary design that makes a full rotation every stitch. I'd say something isn't right in the bobbin or the bobbin case area.
Perhaps a bad bobbin or a burr somewhere.

Joe

ThayerRags

Not trimming off the tail of thread that sticks out when winding a bobbin can cause your condition. The tail gets in the way of the hook catching the loop.

CD in Oklahoma

singerguy

THIS THREAD might HELP . from QB few years back.

Tink's Mom

There were a bunch of bad bobbins made for the #221 a few years back. Try to use an original if possible.

KLO

I was so interested to read this as I always wondered as I did (or did not at times) trim that tail if it would cause any kind of a problem down the road. I will be much more consistent about doing that from now on. It seems to be the little things that sometimes trip me up .... although the big things send me rolling down the mountain!