I had trouble using cone thread with my newer Kenmore machine. The machine was skipping stitches and I couldn't figure out why so I sent it in for service with the cone still on it. The report said that only spools could be used and the needle was wrong too. I had used a needle that would fit Kenmore machines rather than a Kenmore needle. I couldn't figure out how the cone thread fed into the machine differently than a spool, but if I use the right thread and needles, I have no problems. I can go through a spool a day when I get going on a project!
Janie