Class 15 bobbin cases are not all the same
Class 15 is probably the most common style in the world, but class 15 bobbin cases are not all the same. Kenmore models 1301 (left) left side loading, vertical hook zigzag, with flat spring releasing thread right into the 11mm x 3 mm needle L slot opening on top of the bobbin case. 1750 (right bobbin case in photo) front loading vertical bobbin hook system Shorter 6mm x 3mm narrow needle opening slot Flat spring releases thread right at the side of the needle opening on top of case. Singer 15-88 original bobbin case Simanco part # 125291 This is for a side loading, straight stitch only, oscillating hook machine. 15-88 12 o'clock, left leaning finger position, notice the case door latch is flared, curling out, away from the bobbin case, assisting in stitch formation in oscillating hook machines. 15-88 flat hinge spring that releases thread at the base of the stitch finger, some other class 15 bobbin cases release the thread at the needle hole. Finger can be 11 o'clock, 12 o...
