Pfaff 34 Missing Stitches And Pulling Up Bottom Thread

[amuckart]

Hi all,

I've got a couple of Pfaff model 34 wheel foot machines for closing shoe uppers. Both of them are missing the occasional stitch when running at speed, and one of them is pulling the bottom thread up in a big loop so there's an inch or so of it above the material I'm sewing. The two machines are slightly different, one has a standard drop feed and reverse, and the other has a wheel feed with no reverse but other than that they're the same.

The machines are pretty old, but are still tight and the timing doesn't seem to be slipping. I am wondering if the hook/hook race is worn; the one with the drop feed there's a little more 'rattle' in the hook than I was expecting, but I don't know what it should be like when it's right. The points of the hooks on both machines seem to be in good condition.

I can time a machine, but I've never been good at figuring out intermittent dropped stitches and I'm at a total loss as to what's causing the loops of lower thread on top of the work. Can anyone help me out with pointers as to what might be causing this?

Unfortunately I didn't have my camera around when it was doing it and I had to cut the thread to keep working on the machine, but I'll get it to do it again and post pictures.

Thanks.

[Kevin]

I don't know if this might help or not. We've got a Singer post machine at work and you might stitch for a foot and it would be fine, then pull up the bobbin thread for five stitches then sew fine again. I finally figured out we were using the wrong bobbins.

Good luck,

Kevin

[amuckart]

Thanks Kevin. I'm fairly sure I've got the right bobbins for this one, but I'll check. They certainly fit the bobbin case perfectly and the bobbin case fits the hook just fine.

What was the clue you had the wrong bobbins in your Singers?