We have a basic model Singer sewing machine. The spindle that came with it went missing. It fits in a receptacle meant for a six-sided shaft. This is probably the most inane and basic FreeCAD part ever made but it worked on the first try. I'm using it with large thread spools. This machine also has a horizontal spindle that fits under the handle, but it doesn't work well for really large sewing jobs (I had about 36 yards of drapery material to stitch).