Thread raveling

[sofadoc]

I've noticed that my top thread on my Juki LU-1508 tends to ravel and break a little too frequently (maybe a couple of times a day).
BUT, it only does this when I'm using any needle below 23 gauge. As long as I have a 23, no problem.
My theory is that the machine was timed with a 23, and now anything smaller is a little too far away from the hook.
Should a machine be timed with a "mid-range" needle, like a 20 gauge?
Or is there no appreciable difference as far as timing goes?

[bobbin]

That's a really good question and one I can't answer.  But I note that a 23 needle is tantamount to a crowbar!  I work in a marine canvas/awning shop and we generally run an 18 or a 20, bumping up to something larger only when faced with strataglass replacement windows and/or multiple layers of heavily reinforced edges (lacing strips on Coast Guard mooring covers, etc.). 

I never run a needle bigger than a 20 on cushion/upholstery work.  I used a 20 on the awnings for my shop, and I was using 138 thread. 

We had a terrible problem with frayed thread on the 1508 last month.  I figured it was a timing issue, but it turned out to be a problem with the check spring on the tension mechanism.  Maybe that's your issue, too?

[sofadoc]

We had a terrible problem with frayed thread on the 1508 last month.  I figured it was a timing issue, but it turned out to be a problem with the check spring on the tension mechanism.  Maybe that's your issue, too?

That's worth looking into. Maybe if the check spring isn't "checking" properly, it isn't creating the proper loop for any needle below 23 ga.
I'll play with it tomorrow.

I bought this machine from a lady that used it to sew bounce houses. It came equipped with 23ga. needles, and 207 thread. I've never been able to use 18ga. or below without some fraying.

[bobbin]

If you bought the machine and it was adjusted to stitch bounce houses that sucker is set up to stitch through just about anything (including index fingers) it sure sounds like overkill for an upholsterer, IMO.

If you're regularly using 69 or 92 thread you don't want a needle much beefier than a 20.  Anything larger leaves holes that are too big and may destroy fabric threads as they punch their way through.  You don't want that to happen because it compromises the fabric's integrity.  The proper size needle as well as its intended purpose is important.  If you're working on knits you want to be certain to use a ball point needle (it will push the fibres aside, rather than severing them), if you're working on leather (vinyls, too) you want to use a wedge point needle.  As it punctures the goods it leaves in its wake a "hit" with four neat tears, not just a hole.  That allows the goods to close neatly over the thread and leave a more secure hole for the thread to move through in the natural give of wear and tear. 

But I'm rambling.  It's been a long time since things I've learned have been called to the forefront.  sometimes I get carried away.  Sorry 'bout that.

[JuneC]

You're trying to use size V207 thread with less than a size 23 needle?  I'd be very surprised if it didn't shred.  That's big thread!  I thought 207 required a #24 or larger needle.  I use a #18 needle with V92, but it has to be really fresh and works much better if it's the waxy anti-wick.  Typically I use a #20 or 22 for canvas, 18 for vinyl because I like smaller holes.

When you stop and think about it and observe the thread passing through the needle, you see that any given spot in the thread goes through the needle eye and fabric maybe 5 or 6 times (or more, depending on stitch length), back and forth, before it ever comes to its final resting place in the seam.  If the needle eye is quite small for the size thread, it abrades pretty quickly.  Just my observations.  YMMV.

June

[sofadoc]

You're trying to use size V207 thread with less than a size 23 needle?

No, I don't use 207 thread. It just came with the machine. I normally use 69, occasionally 92 or 138.
I've been using a 20 with occasional raveling.
After reading these replies, I think I may need to get it re-timed to accept at least an 18 without raveling.

[RocketmanMH1]

Sofa,  That 1508 is really easy to time for the adjustment you need. If you feel confident I can tell you how to do it. :)

[mike802]

I have found on my machine that the needles eye can become worn over time, this can catch the thread and cause fraying.

[sofadoc]

I have found on my machine that the needles eye can become worn over time, this can catch the thread and cause fraying.

I don't think that's my problem. I'm having fraying right after inserting a brand new needle.

Sofa,  That 1508 is really easy to time for the adjustment you need. If you feel confident I can tell you how to do it. :)

Thanks. But I've got a sewing machine mechanic who owes me a service call. I have timed my own machines before, but I've never really had much luck with lighter weight needles. Even on my old 562, I had to use at least a 20.

[Mike]

sounds like it may be a timing issue.  fwy i also use a #20 with  92 thread

[sofadoc]

I called Gregg today, but his sainted mother said he wouldn't be back until Tuesday. Probably another stint at the porn addiction re-hab center. ;)

Several people here talk about what a swell guy Bob is, so I called him. He wasn't in, but his son was.
After describing my problem, he had a few suggestions. One being the needle guard (that bendable chrome wing on the hook assembly). I flared it out a little bit, so it prevents the lighter weight needles from flexing toward the hook. Then I tried a 19 ga. needle. So far, so good.

Just for grins, I folded some Blue Jean denim over 6 times, and sewed about 30 inches at full speed. It skipped a stitch one time over 30 inches. Probably not unusual, given the circumstances.

[lamx]

Here are some possibilities from my favorite troubleshooting chart:

13.   Cause: The needle is threaded incorrectly.
   Solution: Thread the needle so that the thread passes through the eye of the needle from the long groove to the short groove of the needle.

16.   Cause: The operator pulls the fabric in the direction of sewing.  The Feed Dog cuts the upper thread.
   Solution: The fabric must not be pulled during sewing.  The machine alone must feed the fabric.

22.   Cause: The lower end of the needle bar is bent.  The needle strikes the presser foot, the throat plate, the feed dog, or the hook.
   Solution: Replace the needle bar.

23.   Cause: The throat plate is not held firmly in place and shifts around.  The needle strikes the side of the stitch hole in the throat plate.
   Solution: Tighten firmly the screws holding the throat plate to the machine.

24.   Cause: The feed dog is not held firmly in place and shifts around.  The needle strikes the side of the stitch hole in the feed dog.
   Solution: Tighten firmly the screws holding the feed dog to the machine.

30.   Cause: The thread take-up spring is not adjusted correctly and does not take up the slack of the upper thread.  The needle pierces and tears the upper thread.
   Solution: Adjust the take-up spring.  

31.   Cause: The thread take-up spring is bent out of shape or broken.
   Solution: Bend the deformed spring back to its proper shape, if possible.  Replace a badly defective or broken spring with a new one.

33.   Cause: The hook has burrs, rough spots, or sharp edges that cut the upper thread.  The point of the hook may be blunt or damaged.
   Solution: All portions of the hook that come in contact with the upper thread must be perfectly smooth.  Smoothen the defective portions of the hook with an oilstone or fine emery cloth, then polish with crocus cloth or on a buffing wheel.  If the hook point is defective beyond repair, replace the hook.

34.   Cause: The head of the screw used for adjusting the tension of the bobbin case protrudes too far beyond the tension spring.  This causes the upper thread to catch and break.
   Solution: Adjust the screw so that the upper thread can slide smoothly over it.  If necessary, remove some material from the head of the screw by grinding or filing.  Polish the head of the screw after this correction.  Replace the faulty screw with a new one.

35.   Cause: The top surface of the bobbin case is damaged, or has burrs or rough spots preventing the upper thread from sliding smoothly around the bobbin case.
   Solution: All portions of the bobbin case that come in contact with the upper thread must be perfectly smooth.  Smoothen the defective portions of the bobbin case with an oilstone or fine emery cloth, then polish with crocus cloth or on a buffing wheel.

39.   Cause: The hook is not adjusted (timed) correctly in relation to the needle.
   Solution: Adjust the machine so that the point of the hook enters the loop of the upper thread at the correct time.  

40.   Cause: Some of the parts along which the upper thread passes (thread guides, tension discs, thread take-up spring, take-up lever, etc.) have become rough or sharp and possess deep, sharp grooves.
   Solution: With fine emery cloth or emery cord remove all rough or sharp portions and grooves.  If these parts are too badly worn, replace them with new parts.

41.   Cause: The top edge and inside of the stitch hole in the feed dog have become rough, sharp, or chipped.  This may be due to wear or broken needles.
   Solution: Smoothen the stitch hole with fine emery cord.  If the damage is excessive, replace the feed dog with a new one.

42.   Cause: The needle is too close to the edge of the stitch hole in the presser foot and rubs against the presser foot.
   Solution: Check the straightness of the needle and replace it if necessary.  If the presser foot is not correctly aligned, loosen the screw that holds the presser bar in position; turn the presser bar until the needle goes through the center of the slot (or hole in the presser foot; tighten the screw firmly.

43.   Cause: The needle is too close to the hook and rubs against the point of the hook.
   Solution: Check the straightness of the needle and replace it if necessary.  If the new needle still touches the point of the hook, adjust the clearance between needle and hook by moving the hook somewhat from the needle.  The point of the hook should be as close as possible to the needle without touching it.

44.   Cause: The portions of the presser foot close to which the needle passes are rough, sharp, or chipped.
   Solution: Remove the presser foot and smoothen the defective portions with fine emery cloth.  Polish them afterward with crocus cloth.

47.   Cause: A needle thread of the wrong twist is used, causing the thread to unravel or break
   Solution: Use needle thread with twist recommended for the machine in use.  Left twist thread is required for single needle machines.

Ed

[forsailbyowner]

Had this problem chronically till I replaced the hook assembly. Now machine sews thread it wouldnt think of before replacing. Look for gap between scarf and hook.

[sofadoc]

Just to follow up, the problem was only frequent with needles smaller than 20 ga. After I flared out the needle guard on the hook, I've been able to use 18 ga. needles with no trouble. The smaller "bendier" needles were flexing too close to the hook.
I've always been able to use thread ranging from 45 to 207. I've ordered some 16 ga. needles to see how they work. But I'm ready to proclaim "problem solved".