Yesterday, I ran into a stumper. A Bernette (for Bernina) 50. Yeah, a plastic fantastic.
When I got it on my bench, the hand wheel couldn't turn in a full revolution, and if the needlebar could have gone all the way down, it would have hit the hook. I disassembled, and found several things:
- The hook shaft and the timing gear were twisted - The set screw was still in, but it was no longer set against the flat part of the hook shaft. The nylon cogged "track" or the hook gear had "jumped" and this was what was stopping the handwheel from turning. The gear was spun so that a flat part of the gear was trying to mesh with teeth. Indicating she hit something pretty hard. (The pic is post timing adjustment, but pre-set screw adjustment)
[ATTACH=CONFIG]434292[/ATTACH]
No problem, right? "Easy fix"? Uh.
I timed it as close as I could. Honestly, this machine makes "horse shoes and hand grenades" look like precision instruments!
Moving the gear one tooth turns the hook about 3/8"!
I could either time it so that the timing was behind enough that I though it might skip stitches on the right hand side stitches, or so that the needle drags on the hook. I opted for the skipping stitches side of things, for obvious reasons.
- Now that it's timed, it picks up the needle thread every time, regardless of the needle position while I test manually (turn the hand wheel by hand, and have fabric under the presser foot)
What it doesn't do is let go of the needle thread. It seems like one of two things are happening:
It just hangs onto it and then it rides back around to pick up another needle thread, and we make a nest.
Looking at the hook, compared to a White ZZ machine here (also an oscillating shuttle), it seems like the hook turns further to the left, and further to the right than the White as well, and I can't help but wonder if this has something to do with its unwillingness to let go of the thread. In my mind, this is still a timing issue, but how can it pick the thread up correctly, but not let it go?
I know what the first reaction is: Upper tension too loose.
That's not it in this case. Tension at 9 or tension at 4, the behavior is the same. The machine is threaded correctly, and the thread fully into the tension disks, which are clean. I'm using a Schmetz 15x1 90/14 universal needle which interestingly is slightly longer than the unbranded needle she had in the machine by about 1/16". The manu al calls for HAx130 needles, which as best I can tell is interchangeable with the 15x1. The thread is Gutermann Sew All Polyester, which is about a 50 wt thread.
- The hook seems to turn more than the White ZZ machine (also an oscillating hook) I have here, though their hooks are interchangable. It seems to rotate further left than the White, and it has a greater degree of rotation. Which seems odd and extraneous...
- The other thing I've noticed is that the take up lever is almost 1.5" from it's highest point when the needle is at its highest point. The take up lever hits its highest point when the needle is well into its downswing. It's the only machine like this in the house. Yes, I spun at least 8 of the machines last night to test this theory.
I've been focused on timing the hook because it was obviously wrong, but I'm starting to think this is bigger than that.
I would appreciate any and all suggestions as to how to resolve this. I feel like I'm so close, but getting so frustrated..