Crazy bobbin case (& it's willing accomplice - the bobbin) roll out of the shuttle
 

I had a bit of trouble with a Japanese 15 last night. The bobbin case and bobbin would roll out just as soon as I put it in. Some times it would actually stay in. I was going CRAZY... Things can cause - maybe more - maybe someone else will know...
ONE. The take up lever has to be ALL the way to the top of the space (this is true on my modern industrial sewing machine, too - it has a mark on the machine for where the bobbin will go in and it is the same position)
TWO: Be sure the bobbin is not bent or warped and fits in the case flat - any defect can cause the whole thing to roll out.
THREE: Be sure the thread is clear of the area - it should be sticking out - not in the path of the bobbin.
FOUR: Make sure the tail from the bobbin winding is cut off and not making the case stick out too far.
I'm sure there can be other causes of bobbin case and bobbins rolling out of a machine.

FIVE: Make sure the bobbin case latch is clean, free to move and that the latch spring is not broken.

I was just going to say that the latch spring might be broken...you can get a replacement bobbin case. It may be worth it to save aggrevation.

Susie's right about that. We keep extras in our bobbin box.

Oh, FYI, there are at least two variations of the Class 15 bobbin cases for the Japanese machines, possibly more.

Short needle slot: If the machine is a vertical end loading ZZ the bobbin case will actually move left and right with the needle. It takes a case with a short needle slot.

Long needle slot: If the machine is a vertical front loading ZZ the bobbin case is stationary and the needle needs a wider slot so it does not hit the case.

Straight stitch machines use the short slot case as OEM, but can actually use any of them.

Joe

It did it with a different bobbin case so I did a clean up with some solvent - must have had some dried on oil. Seems to help.

When you load the bobbin into the bobbin case, the thread should pull counter clockwise.