Hello Wanda,
I think you may have the black apollo bobbin case, it should slide on quite easily but it sounds like the metal finger on the top right hand side that holds the bobbin case in is loose, make sure the screw is tight, when you have the bobbin case in push it with your thumb to the left and look at the gap that the thread passes through, there should be anough space for the thickest thread to pass through normall a number 40, if the gap is too wide the bobbin case will jump out. drivewithken@blueyonder.co.uk
Ken
drivewithken@blueyonder.co.uk, November 2007