Hi! First, I hope I am doing this right. If not I apologize in advance....Last summer, I inherited a 306K Singer..sews like a dream. I would love to piece quilt tops...Not sure how to get a quarter inch seam. I tried the zipper foot, which allows for the needle placement. This leaves the feed dogs open and pulled threads down into the bobbin area, locking up the needle. Had to have repairman to get the threads out....hoping someone here can help.