Hi!
I've recently started sewing in my home for a local small business as a night job. The owner loaned me a 319 to get started with and I've recently purchased a 1958 306w. The hook assembly in the 306 was noisy with a chatter that seemed extreme and different than the voice of the 319. I found this thread
Singer 306K help very helpful and downloaded the service manual!
I found that the hook assembly position finger engages the slot in the hook assembly slightly differently between the 319 and the 306. On the 306, the tip of the finger is a few thousandths wider than the corresponding slot in the hook assembly. So, this can never be adjusted to a 0.020" gap as the service manual specifies. (On the 319, the tip of the finger can pass in/out of the slot for about 0.040" of depth with a couple thou of clearance on each side.) Also, it appears that the bobbin thread path out of the bobbin case passes to the left of the position finger and not under the tip of it in what is supposed to be the 0.020" gap.
If I adjust the finger such that the hook assembly body doesn't spin but the finger is tight enough to keep the bobbin thread under the tip, it won't sew without accumulating the stitches under the finger's tip and binding up the machine.
With the bobbin thread routing left of the finger, it sews exceptionally with one exception. I have to start the first stitch with a long thread tail because it sucks about 1.5" of it back down into the plate with the first machine motions. That seems strange and that (well, along with the clackety rattle) is what I'm trying to improve. Is this "left of finger" bobbin thread path standard in some machines?
I will post a picture. Thanks for any advice!!