Random Loose Top Thread Consew 289Rb-1

[coryleif]

Hi guys,

Before I continue tinkering with my machine, I thought I'd see if anyone has had this problem before and can offer a solution.

I have a new-to-me compound-feed post-bed machine. Sometimes it sews fine more miles, sometimes it throws out random loose stitches on the top thread (see photo), usually when I'm sewing the finishing stitches on a bag. Seems like what's causing this is: after the stitch has been made and the needle is coming up and the take-up lever is pulling up the top thread and the bobbin thread into the fabric, the top thread rubs against itself and pulls up a top-thread loop. Usually everything is pulled back down tight before the center presser foot comes down, but it looks like sometimes the foot stomps on the loop and keeps it there.

Is this simply a top-thread tension issue, or is there something more sinister at play?

In the photo, I'm sewing with T90 bonded poly thread (black), #20/125 needle, on acrylic (Sunbrella) canvas.

This machine came set up for leatherwork, but I have it set up for canvas currently. It had this problem when I got it, though (with a heavier needle/thread setup and with cotton canvas).

For canvas sewing, I have replaced the thread tension assembly, the bobbin spring, and switched out the feet.

The bobbin is rotating opposite the direction of the hook. There is no anti-backlash mechanism. I'm still working on getting the bobbins wound evenly; the bobbin winder supplied was set up for a much smaller bobbin than the 289's U bobbins.

Thanks for reading!

cory

[Uwe]

Nice machine! I had to look it up actually and Leif Labs had a nice photo blog entry on the Consew 289RB-1. That seems like a HUGE bobbin for a post machine. Now I want one - nice going!

If the thread "sticks" and gets pulled up with the needle from an already formed stitch, that will definitely mess up that upper stitch loop. The thread needs to easily slide through the needle's eye AND the long needle groove to make a good stitch. When the thread take-up lever is in the top position, the top loop for the previous stitch needs to be tight, otherwise you're doomed.

Does this happen only at speed or also when you manually turn a few stitches? It's often hard to tell what's happening at speed.

A few options I can think of:

1. The needle may be too small and the thread gets stuck in the long groove of the needle as it goes up. The thread is supposed to easily slide through the needle's eye AND the needle's long groove. I recently read one needle-to-thread size test that said to press the thread into the long groove of the needle - if the thread sticks in the groove, the needle is too small.

2. The thread may need to be lubricated to facilitate sliding through the holes and channels. Perhaps the polyester thread and fabric are sticky to each other or the thread is sticky to the needle.

3. The thread take-up spring setting may also play a role. This spring is supposed to keep the upper thread taught until the needled enters the material again. The spring should come to rest on the adjustable support just as the eye of the needle goes into the material.

4. Make sure the basics for threading and timing are good, and that the needle has the long groove facing away from the hook and the scarf cutout of the needle facing towards the hook. With the needle turned around 180 degrees, the hook may still be able to pick up the thread and make stitches, but the thread will be tight or loose in all the wrong spots and at the wrong time.

I made a little close-up video some time ago about the hook area of a Consew 225. What surprised me when I made the video is just how much (and how often) the same section of thread thread gets pulled through the eye of the needle (and through that long groove along the needle). The video also shows how the thread still gets pulled DOWN though the long groove on the left as the needle ascends. For the thread to get pulled back up through the hole to loosen the top loop, it would really need to stick to the RIGHT side of the needle where the scarf is. Not sure how that would happen, actually, unless the material squeezes very tightly around the needle and the thread stick to the needle.

[Uwe]

Wait, are YOU the Leif of the lab? I didn't even look at your name before I posted. Nice blog, by the way, I've been there quite a few times.

Edited January 18, 2016 by Uwe

[coryleif]

Thanks for the quick and thorough response, Uwe! That is my blog (thanks again) ... which, now that I think about it, is mostly about my terrible luck with machines.

My Singer 20U also does this sometimes. With that machine, I suspect it is also the foot preventing the stitch from setting after it's popped up. I have the newer Chinese-flavored machine. I was checking out one of those sexier blue 20Us and noticed that its regular foot has a beveled underside behind the opening that would allow the stitch to set w/o interference. The new foot on my machine has a comparatively hard edge. I've recently got a teflon foot and cut it out underneath a bit with good results ... but I digress...

Yes, this is a super-cool machine, especially for bagmaking. I didn't know I needed one till I saw how they make L.L. Bean totes. Maybe I was a little too eager to get it ... and overlooked some of its faults. Ha.

This happens at speed (though I don't sew very fast) and hand cranking. I haven't been able to catch it at just the right moment yet and inspect all the thread paths.

To clarify: the top thread pops up after the needle has exited the fabric. Seems to be a thread-on-thread situation, somewhere after the 46-second mark on your video, before the knot is pulled up. If you can imagine that both sides of the top-thread loop are moving up through the material at 0:49, I think that's what's going on.

1. #20/T90 is a pretty standard thread combo. I use it w/o issue on my other machines. This Sunbrella has a pretty tight weave, though, so maybe a larger needle might help.

2. Since the thread is black, it's a little on the rough side. It's not super fresh either, so lube might help. Do you have a preferred type/source for canvaswork?

3. The take-up lever looks okay. Though, that's good to know how to time it properly. Always been a bit of a mystery to me.

4. Without removing the feed dog, the timing seems pretty good (but I don't think the needle is kissing the guard). I've never had any skipped stitches; though I did have a backlash-related jam (I think) ... but I might've had the bobbin in backwards. Still haven't looked into the latch-opener timing enough.

The feed-dog hole is chewed up a bit. I should probably smooth it out. Something could be getting caught in there.

I might shave off the heel of that foot so it's not pressing so much on the stitch. We'll see.

Thanks for your help, Uwe! I've been spending most of my Internet time on this forum these days (years) and I have to say, your videos are a nextlevel addition. I wish I knew what I know now 10 years ago. And there's still so much to learn...

cory

[Uwe]

Sounds more like a thread issue then. Perhaps the thread has a rough enough surface or hard/brittle outer layer (either off the spool or after squeezing through tights spots enough times) so that when two opposing jagged edges meet just so inside the hole, the thread gets pulled back up with the ascending thread. Once the thread is pulled back up, there's really nothing in the stitch cycle that pulls it back down again other than the presser foot occasionally and accidentally stomping on it just so.

I'm not a thread expert. I've only really sewn with bonded polyester thread so far, which I bought at thethreadexchange.com

I have a few old spools that came with machines I've bought. Some of it is in rather rough shape (my black thread looks like it has a dandruff problem!) so I wouldn't want to use it for actual for-sale projects. Thread probably should come with a best-used-by date stamp on it. It may last much longer once it's sewn, but the actual sewing process may require new enough thread that is still limber and hasn't lost it lubricating properties yet.

If I were you, I'd buy some nice, high quality new bonded polyester or nylon thread and see if the thread-loop-pull-up problem still happens. Polyester thread is supposed to have improved sunlight resistance properties, otherwise it's nearly identical to nylon. Some threads come pre-lubricated. Thread in itself is a bit of a science and I haven't quite figured it out yet. But new thread has a more-predictable-quality advantage over some old who-knows-what-happened-to-it spool.

[Wizcrafts]

I also prefer lubricated thread. Cowboy makes lubed thread. Weaver Leather sells a heavily lubricated bonded thread that has so much lube that it drips all over the machine guides and tension disks.

You can buy a magnetic lube jar from various industrial sewing machine dealers. It sits on top of your machine and the thread passes down and back up, through whatever you fill it with. Liquid sewing machine silicon works best and won't discolor fabrics. I get mine from Toledo Industrial, in quarts. I think they may also sell the magnetic lube jars.

[coryleif]

Thanks, guys!

I'll start experimenting with different thread and see what I can see. I'll also look into that silicon lube -- that seems promising.

[Now that I think of it, the bottom thread guide has a felt pad in it -- that's probably for lube. ]

This is Coats Ultra Dee thread, which I got from an upholstery supplier. I've had good luck with it over the years. Though, like I said, it's not exactly new.

It's curious that this doesn't happen with my other machine (Tacsew 111) with the exact same thread and material.

I'll keep diggin'.

Thanks again!

cory

Edited January 19, 2016 by coryleif