Stitch unbalanced every few stitches

[the deacon]

I have been trying to dial in my Juki 341 for the past month. I'm not at the point where I'm not sure which variables are effects which outcomes (though I have been trying hard to only change one variable at a time).

I can't get the center of my stitch consistently in the middle of the material I'm sewing (example here is two ply #10 canvas duck, size 16 needle, 69 bonded nylon thread. I have used yellow thread in the bobbin to highlight the issue). Seems like every 4th stitch or so the stitch pulls toward the top of the material. I have adjusted the tension and it doesn't eliminate this pull up every so often.

Thanks for the help all.

[DrmCa]

Provided that the machine is threaded correctly, I would suspect a burr on something round which is rotating with the thread. That could be a bobbin, or disks on the tensioner, etc. Did you try a new bobbin?

[the deacon]

good thought. I have tried a new bobbin. I looked at the tension discs, couldn't see any burrs

[Yetibelle]

When you see the bottom on top - that is typically to much top tension that's pulling the bottom up.  Your not far off.  That is just 2 layers, does it still do that on 4 layers?  

Handy chart. 

 

[Techsew Ron]

4 minutes ago, Yetibelle said:

Handy chart. 

 

 

Great chart - I often use the "tug of war" analogy whenever explaining thread tension to someone.

[R8R]

I get this sometime with two layers of heavy nylon (1050 ballistic)

I start by backing off both tensions then creeping them back up equally till the balanced tension is acceptable. If the tensions on both are too high, little inconsistencies can have big effects like the tension jumping and pulling to one side, etc. I always go for minimal tension to make a good stitch, and minimal feed pressures.

 

Also, sometimes adjusting thread guides (if adjustable) can effect thread take up and fix minor tension tweaks.

[sheathmaker]

Try an #18 needle and see what happens.   My 69 thread likes the 18 much better.

 

Paul

[R8R]

1 hour ago, sheathmaker said:

Try an #18 needle and see what happens.   My 69 thread likes the 18 much better.

 

Paul

Ah! Just noticed after this post it was a 16. yeah I always have WAYY better luck with an 18 and 69. Too much thread bunching and breakage with a 16, especially on coated woven materials.

[Wizcrafts]

Keep an eye on the thread as it unwinds from the spool. Follow the thread as it makes its way to the top tensioner disks. Watch for any sign of binding as the thread comes of the spool. Watch out for twisting that forms loops and knots in the top thread. Either of these things will increase the top tension temporarily, causing the knots to move up.

[the deacon]

Thanks so much everyone! Great suggestions. I'll try them out and report back.

[the deacon]

ok, moved up to an #18 needle and still had the same issue. Then did 4 layers of the #10 duck and that worked much better, if I look closely (and into the needle hole) I can see the knot favoring the top side. This doesn't solve the problem as my work only calls for 2 layers.

No knots or twisting happening through the thread guides or off the spool

this one is stumping me.

[Yetibelle]

I suspect the bobbin tension is off, could be you need a new bobbin-case-spring?  It may look correct, but just not have the right pressure on the thread anymore?  If you can load some pictures of your bobbin and case and hook, maybe someone will notice something?

 

[Wizcrafts]

2 hours ago, the deacon said:

ok, moved up to an #18 needle and still had the same issue. Then did 4 layers of the #10 duck and that worked much better, if I look closely (and into the needle hole) I can see the knot favoring the top side. This doesn't solve the problem as my work only calls for 2 layers.

No knots or twisting happening through the thread guides or off the spool

this one is stumping me.

Try reducing the tension or travel of the check spring. Consult your manual for how to do this, or Google it.

[Colt W Knight]

Had this problem with my consew 206, turned out the tension discs had worn a groove.  Took them apart and polished the groove away with s Drexel and buffing rouge . Problems went away.  I ordered a replacement tension setup, and half the psrts were unusable (Didn't  fit), so I ended up piecing stuff together to replace all the worn out parts

[Matt S]

@the deaconForgive me if I'm pointing out the obvious but have you tried with a fresh bobbin? I have found that unevenly wound bobbins can cause these sort of inconsistent tension issues and they aren't always visible once the bobbin has been filled.

[Bugstruck]

As someone mentioned that can occur with ballistic nylon but that is largely fabric driven and duck does have some cavity to it bit I haven't experienced it with that other than very limited/rare. I'd say bobbin or bobbin tension to start and I would be inclined to tighten it up to start (if that doesn't bunch the fabric) and then go opposite if that doesn't help. If that didn't improve things then I'd eye the top thread action below the needle plate as possible. A top thread intermittently catching or hook timing on the edge of right can cause some variance with how that top thread snaps up on pull. I assume you aren't novice enough to put the bobbin in backwards like someone I am. Fought a stitch balance isse for half an hour one evening before I figured that one out??? Plain stupid. Work back towards the spool from there. I also assume you are having the problem across multiple fabrics. Punching holes one size over the recommended needle size is rarely but sometimes revealing too. Helped balance the stitch on that ballistic material.

[Bugstruck]

Forgot to second Wiz's comment on the check spring. Seating as the needle enters the fabric. Then tension.