Bobbin issues with a Signer 31-15

[ponygirl]

Hi all,

I recently purchsed a Singer 31-15 which was sewing nicely until this afternoon. The issue appears to be the bobbin. I've made sure that I'm winding and picking up the thread as instructed. However with the bobbin and bobbin case in place, either the flywheel will not turn or it will turn but the machine will not sew (in other words, the wheel turns but the mechanisms which run the needles don't move). When it does work, it moves with an erratic, jerky motion. With the bobbin case removed, the machine moved nicely both manually and with the motor.

I'm not sure if the bobbin case is locking in properly. Could the case be worn and need replacement? I've checked to make sure there's not thread getting caught anywhere inside.

Perhaps I'm just making an obvious newbie mistake that is going unnoticed, or perhaps a part is worn. Will inapparopriate thread size cause any issues here? I am running a 69 top and bottom polyester apholstry thread. Any insight is much appreciated!

[Tkleather1]

well I run the same setup and I havent had any trouble in that aspect. if the timing is off I think it might cause problems. but if the flywheel is moving and the needlebar is not it seems that something might be broken somewhere to me but I am not very versed in the inner workings of a sewing machine.

[torrbuidhe]

The thread size is well within the capabilities of your machine. I sounds to me as if the needle might be hitting the bobbin case. Try taking off the bed slide plate and needle plate, this should give you a better view of what's happening.

31-15s dont's get out of timing as such because the shuttle drive shaft is pinned at both ends. It is possible for the needle bar crank to shift on the top shaft (at the right hand end, it drives the needlebar up and down) which is effectively a timing issue. You should also check the feed drive eccentric, behind the cover on the back of the arm, this times the feed dog to the needle/thread take up.

Also if the needlebar has moved in the needlebar clamp the needle might be set too low which would make the needle hit the bobbin case.

hope this is some help