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A year ago I loaned my Brother XL-2600i to my kid's school, and only now have I tried using it again. Yep: they messed it up. The thread tangles up around the bobbin, and it makes grinding noises.

Disassembling it, I found a broken needle inside, under the bobbin case. I removed that, cleaned it all out, and still it isn't functioning smoothly. So, I'm guessing something got bent when the needle whacked into it and broke.

Trying to figure out what got bent, I disassembled everything, trying to find out what isn't working smoothly. When I removed the bobbin case, I revealed the drum with the hook that holds the bobbin, and turns under it (the black hook is visible on the right under the white plastic piece):

Drum and hook under bobbin

Now the drum spins smoothly, and there's no more grinding noises (not surprising, as there's not a lot there). However, if I replace the bobbin case, when I run the sewing machine the bobbin case rocks back and forth (moving about ½ mm each way):

Bobbin case

It looks as if when the hook moves under the bobbin case it pushes the case back and forth.

Here's the question: is this normal motion of the bobbin case? Or should the bobbin case be truly motionless, and this shows that my problem is with the case and/or the underlying drum?

(I'd also be happy with any other suggestions of what might be going wrong.)

Edit: I'm adding some more information that led to the solution. When malfunctioning, the loops of thread under the cloth being sewn that should have been pulled tight, weren't. Each time I tried sewing I had to pull a wad of these loops out of the mechanism under the sewing platform. Here's a picture of the loops (showing the underside of the cloth):

Loops in sewing thread

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The bobbin case rocking back and forth is normal! In order to form a stitch, the top thread has to cross under the bobbin thread and back up. It does that by looping all the way around the bobbin case - you're seeing the wiggle room to allow that, called the escapement.

It is hard to say what the problem might be from your question, but has the machine been oiled recently? Cleaning, oiling, and new needle cure a lot of machines.

  • I'd forgotten that the thread gets pulled under the bobbin case; now I'm wondering if there are catches on the bottom of the case that I could clean. BTW, on this model, the FAQ for "Where do I oil?" is "Don't!". – Daniel Griscom Jul 20 '18 at 11:23
  • @DanielGriscom I am perpetually amazed at how much lint and thread can hide in the bobbin area of a machine, so hopefully more cleaning does it. And wow, I've never seen a graphic more accurately summarized as your "don't" link. :-) Cracked me up. Good luck! – Reve Jul 20 '18 at 12:59
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Reve gave me the tip that led to the solution. As part of each stitch, the upper thread has to be pulled around and under the bobbin case; the loop is then pulled tight against the underside of the cloth. But, in the process of chewing on the broken needle, the bottom of the bobbin case was scored and abraded, and the thread wouldn't smoothly slide under it. This left the machine unable to tighten each loop, and all hell broke loose.

I checked, and although it wasn't obvious, there were clearly rough spots on the bottom of the bobbin case. I used fine sandpaper (280, 320, and then 600 grit) to clean off every rough spot I could find. I reassembled, and I believe the bobbin case was rocking less than before (although it's tough to tell). But, the most important change: it all works again. Yee haw.

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I had a similar problem and the result looked the same (neat stitches on top and a chaos of loops on the bottom).

In my case the bobbin case jammed when I inserted it into the machine. It looked like it was sitting in the right position, but it wasn't pushed all the way into its slot. As a result, the bobbin case protruded a millimeter from its case and the thread got caught.

A slight push on the bobbin case every time after inserting it solved the problem for me.

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