Repair manual Bernina 1001 or 1000-series?

Hello Tim; Thank you very much indeed !! Not all, but I do recognize in this manual similar components as in my 1001. The 1001 is, as the 1008, a fully mechanical machine and therefor I hope that I can solve the problem. For now I'll concentrate on the bobbin area. When slowly hand-cranking the machine the bottom thread is still slack when the top-thread tightens the loop. This causes the bottom-thread to lay as a rather loose chain of "S"-shapes (or weave pattern) on the bottom of the fabric. This happens regardless how tight I screw the bobbin-case tension-spring. The bottom thread seems only to be pulled tight at two occasions: 1) When the feed-dogs advances the fabric and 2) when a "hump", on the opposite side of the rotary hook strikes the bottom thread; but that happens after the top-thread has tightened the loop.

Hopefully with this manual I can now check all the settings & timings and perhaps find the culprit !?

Thanks a lot again and I'll let you know ;-)

Best regards: Endeavor.

Hi Tim;

Just to let you know that the 2nd part of the manual with the Bernina 1015/1010/1005/1004 & 1000 information was very helpful. I went through all the check-points and found only the hook-timing off by a 10-15 degrees. Adjusted the hook-timing according to the manual. Top-tensioner, bobbin tension, feed-dogs, needle position etc all fine ....... unfortunately the loose bottom thread problem persist, clearly visible when the maximum stitch length is chosen. The bobbin thread seems very loose when the hook wraps the top-thread around the bobbin-case. I just can't find out why or find any decent information how it supposed to be with, or the exact working of, a rotary hook.

Any further (rotary-hook) information is very welcome ;-)

Best regards: Endeavor.

Ha, I didn't even realize the second part of the manual was there. Good deal.

https://en.wikipedia.org/wiki/Rotary_hoo... - this has a good animated graphic of the rotary hook operation.

I'm not a sewing machine tech, but I can't see any other cause than something wrong with the lower thread tension. Look at section 54.1 of the second part of the manual that tests the lower thread tension. Do you have the weights they refer to to test the tension? If not, I would progressively tighten the bobbin case adjusting screw to see if I can't tighten up the lower thread. Worst case, try replacing the bobbin case.

Hi Tim; I tested / adjusted the bobbin-tension with a 5 gram weight. The problem stays., even though to a lesser extent, when I tighten the bobbin spring to the max. (at which the thread pulls really tight out of the case). Also tested the top-tensioner with a weight and that one was more or less "spot-on". To lessen the problem, and to pull the bottom thread tightly up ("through" the fabric), I've to sew with the top-tensioner set at 8-to-9 (out of 10).

I have a new bobbin case; same problem. I've seen the sketchy animation and understand the principle fully. I'm now trying to study / find information on how the the process exactly goes at every moment in time (per degree if you wish); hook position / bottom tension / top tension, needle-postion vs pickup-lever vs feed-dogs.

Agree, something happens at a certain moment time that causes too much slack in the bottom thread. The minor detail now is to spot that moment and what causes it. I'm still full of hope !! ;-)

We'll soldier on and I will let you know !