The Sewing Place

Bobbin tension versus upper tension?

MrsThrifty

Bobbin tension versus upper tension?
« on: May 05, 2018, 14:08:01 PM »
New mum brain- this might be a daft question... When you raise the presser foot aka take-up lever, the upper tension discs release and the thread passes through without trouble. All good so far. The question I have is- does any part of that process work on the bobbin thread?? I am currently using an Bernina 850 Industrie. The bobbin is a Oscillating Hook type, the bobbin case tension is fine when using the drop-jiggle test, however the thread gets really tight upon inserting- a bit like what it feels like when you pull on the top thread with the tension discs closed...

It's only becoming a bother when I raise the foot to cut the thread. I think the stitch formation seems alright (still fine tuning), but the difference in drag when pulling both threads out is noticeable enough to ask the question regarding whether tension is released at the bobbin when raising the take up lever? Anyone? Any thoughts? My newer computerized Janome doesn't suffer from tight bobbin thread, but it's a newer drop-in type bobbin.

arrow

Re: Bobbin tension versus upper tension?
« Reply #1 on: May 05, 2018, 15:03:33 PM »
 I think my old 730 has much the same hook and race as your 850 (I think the 840 is the rotary hook high speed version) and the same top tensioner as on your model. I would take out the bobbin case, hook and needle plate to see if there might be something that might need to be cleaned out. When you pull the bobbin thread (after it's been take up through the needle hole) there might be slighly more tension, but could it be you need to turn the hand wheel  a bit to get the needle bar in top position? Tension tend to be very easy and forgiving on these models. The first drop-in bobbin case came in year 1900, when Singer model 66 was introduced, it has been improved a bit over the decades, with or with out fancy features, but basically much the same.
« Last Edit: May 05, 2018, 15:08:55 PM by arrow »

MrsThrifty

Re: Bobbin tension versus upper tension?
« Reply #2 on: May 06, 2018, 09:42:29 AM »
Thanks for the help Arrow, I de-fluffed under the needle plate and oiled the race, and had a look for any snagged threads or stray pins! I still can't figure out how to remove the hook, but I don't think that's the problem, thankfully! I had ordered a replacement bobbin case to replace one where the tension kept loosening (stripped screws, it had been sewing horse rugs before it was mine, very different needs!!). I thought the new one was good, turns out it's not.  >< The new one has a teensy weensy bump inside the case where the little insertion lever joins... and it's about 0.5mm-1mm proud of the rest of the innards, causing extra pinch-type tension or drag once inserted. Time to crack out the dremmel to shave a little bit off. I will post back once I've tried that!

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Re: Bobbin tension versus upper tension?
« Reply #3 on: May 07, 2018, 00:01:49 AM »
Did you buy a generic bobbin case or Bernina brand? I think the bobbin case in theory is much the same as model 15 and loads of brands still use it. The problem is all models and makes aren't exactly the same, and tiny variations can act up on one model and not on others. Another thing is rough polish and finishing, like on 66 / Apollo bobbins, they are in theory interchangeable, but production vaires too much and problems are more common than you know. I have ordered quite a few to get a dozen that works.

MrsThrifty

Re: Bobbin tension versus upper tension?
« Reply #4 on: May 25, 2018, 03:45:08 AM »
It was a generic one, going by the price, but was purchased through a known sewing machine retailer, so I was hopeful.

I got hubby to grind down the offending part inside. It made no noticeable difference, bummer. Then I figured I had nothing to lose so took the tension assembly off the new one and put it on the old one. Not a clever move either. Those tiny screws are a pain to reseat properly and I got cross threaded a few times and somewhat stripped the heads trying to get some semblance of tension back. *shrugs*

Lesson learnt, I have since ordered a true-blue-fair-dinkum GENUINE replacement part from one of the only Bernina service centres in my city and it's being sent out today. :) Should have gone that way first!