Originally Posted by cabbagepatchkid

Are you getting a mess of thread on the underside of your fabric?

In the book "The Featherweight 221 and I" by Dave McCallum he says that if the machine was recently cleaned and the throat plate removed to clean the dust bunnies from under it, then sometimes the bobbin case "finger" is not in the little slot that it has to be in before putting the throat plate back on.

The other thing that he mentions is that if the machine has not been cleaned then it could be packed with dust bunnies, causing missed stitches and can also cause the thread to form birds nests.