Inconsistent bottom stitches - HELP!

[JimRaynor]

Hello friends,

I've got a problem that's been plaguing me for the last few weeks, whatever I tried, did not work.
Well, a picture is worth a thousand words.. The attached picture is the bottom of 2 layers of nubuck glued together.
While the top stitching (not shown) is good, at the bottom (the picture); some steps are good, some are bad, some are almost perfect and some are completely unacceptable.
The whole thing was done on a single run with no variation in speed.
This is what a few months old Juki LU-1508N gives me...
My other machine; LS-1341 sews the same material absolutely FLAWLESS - same needle, same thread, same operator, etc...

I'm very frustrated.

All help is appreciated and I thank you in advance.

[brmax]

Totally understand the frustration, and wish I had a clear answer rather than having had some of the same.

Something I found tough how to describe is the consistent stitch issue, so will say I have found the very same in my general settings to show every 8 stitches this part was consistent, but showing up as a loop on the top fwiw. I ran through some troubleshooting and I'm sure missed many things, what I had done before on all my machines was going through and by the book setting specs to the manual each step, but knowing that I don't but some pros understand a tweak here and there "and what it does".

I did follow up with making the hook/needle guard have slight pressure in its rotation against the needle on my 08 but inline on my 212 hooks. This issue I had pretty much eliminated finally with more tension on upper adjustment.

The best problem solving here is going to be from the pros on the site here, and I surely welcome the help in this specific issue. I wondered many times that it maybe myself operating and the movement of material during the stitch line/seam. This is also with a 1508NH I'm referring to and also as you mention same material runs fine through a 212, or 1341 so there's a catch in its getalong I haven't yet tuned!

So I'm interested in some thoughts here from the experts as it is weird because my stitches were perfect also except pretty darn near 8-10'th then a top loop. Now with more top tension I'm rolling on fine now, but its not a clear answer for myself and so I'm in line for hearing answers to your question also.

its Good that its Friday

Floyd

 

[JimRaynor]

Thanks for taking the time and replying brmax.

I too found out that increasing the top tension somewhat reduces the problem but does not eliminate it.
And when I say ''increasing the top tension' I mean increasing to a such point that the thread almost cuts my finger when I try to pull/loosen it a bit so that I can get the material out under the walking foot to cut the threads.
That's of course very unnatural thus telling something else is wrong - not the relative tensions of the top thread and bobbin thread.

It's a fact that the thread tension(s) (top, bottom or both) somehow varies during the run.
I thought a piece of thread could be stuck somewhere around the bobbin and looked high and low hoping to find something but found nothing. That would have explained the problem.
I don't know what else to think of...

There are really very experienced people on this forum and I'm sure we will find out what the underlying cause is and the rest will be easy.

[CowboyBob]

Which bobbins are you using,I've had people w/the same problem that bought cheap bobbin off flea-bay,they were out of round.Try pulling on the bobbin thread n& see if there's any tight spots.

[brmax]

I seen someone on a video demonstrating some auto upholstery stuff and picked up on this tip, and myself think its great and have about made it a habit; When finished with the sew / seam and presser foot is down and lever is up, I pull thread just below the lever, this making some thread slack for easy pulling material away for a thread cut.

I am not sure what I did but its working, I have to admit I don't have Juki bobbins and did get some from online supply. Its very possible and will add I did get the caliper out long ago when purchased way way back as something was a bit different in the rewind stem with these bobbins and so a tweak of that split stem was remembered so that's noted. I would like to try some pre wounds but again its working at this time and in the center of the materials. So will keep an eye out for factory bobbins for sure.

The thread tension as you mention sounds familiar, and its not like you can measure with a tool as easy as the side loaders. Would be curious to hear a standard method of bobbin tension measure, other than a bag sewn and weighted? or if that a measure amount.

Floyd 

 

[JimRaynor]

2 hours ago, CowboyBob said:

Which bobbins are you using,I've had people w/the same problem that bought cheap bobbin off flea-bay,they were out of round.Try pulling on the bobbin thread n& see if there's any tight spots.

Thank you for chiming in CowboyBob.

Actually yeah, I use some cheap bobbins off of ebay however I've tried pulling out the bobbin thread a few yards at a steady speed with my hand but did not feel any changes in friction/tension.
Thinking I might not be sensitive enough, I've switched to the original 2 that came with the machine and the problem was still there...
So I think it's safe to say in my case it's not the cheap bobbin.

[JimRaynor]

1 hour ago, brmax said:

I seen someone on a video demonstrating some auto upholstery stuff and picked up on this tip, and myself think its great and have about made it a habit; When finished with the sew / seam and presser foot is down and lever is up, I pull thread just below the lever, this making some thread slack for easy pulling material away for a thread cut.

That's the exact same technique I was talking about when I was giving the example of top tension being so high that doing this feels like the thread is cutting my finger!

[CowboyBob]

Do both of the machines have the same amount of tension on the check spring?(The one that moves while your sewing)

 

[JimRaynor]

20 minutes ago, CowboyBob said:

Do both of the machines have the same amount of tension on the check spring?(The one that moves while your sewing)

Hmm, interesting point...
I'll definitely check that when I get back to the workshop and let you know CowboyBob.

[JimRaynor]

19 hours ago, CowboyBob said:

Do both of the machines have the same amount of tension on the check spring?(The one that moves while your sewing)

In hopes to find out that there was a huge difference between the tensions on the checker springs of the two machines, got frustrated once again...
They were very close if not identical...

Thanks for trying CowboyBob.

[brmax]

The problem I was running up against led me to looking at each machine " I thought they were the same" but anyway just taking a look at the thread path, surprised they worked but different and why I thought they were the same was my head down moment! wha?

So I rethreaded through the guide post on them the "same" and did a recheck, re-sight and decided to change needles from a 18 to 19 running 92. Working through these changes were the biggest part I believe. The option to use all the guide holes for thread in the piece above the winder is a choice one has to make, and the route described is experimental. I will admit keeping things the same on these is great by me most all the time, but here on the 08nh, I run thread one loop through the upper thread guide between post and tensioner in this change.

This model is a bit difficult so I guess it gets its due, They made it to be a bad az and so here this round I'm standing.

After reading Bobs post I looked at the check springs here and they are positioned the same headed to 9:00, as to any measure of them I haven't experimented getting any figures, that really maybe the difference one could measure, also here these are oem springs. 

What kicks this to a thread path I think is (it looks as mine did) not every stitch, like a hook issue might be. So right now I'm in the area of watching mine and listening here as the others offer up some great tips and checks as they have already, I appreciate the help, and good luck Jim

Floyd

 

[JimRaynor]

Thanks Floyd for taking the time and sharing your experiences. I really appreciate it.

Today I've cleaned, oiled, re-threaded the machine and changed the needle...
Still, no avail...

I'm starting to think it's got something to the with the hook mechanism too...

[RockyAussie]

The picture you have given is a bit short to go by but it looks to me that every 6 to 7 stitches you are having a too tight pull with the bobbin. This could be by the thread cone being a bit offset and going loose as it straightens up every now again. Sometimes when cones get close to finished they can do this a bit also. If you don't have a second bobbin case to try take a picture inside of the case and see if you can see any burring anywhere.(And post it). If the bobbins have a slot for loading the thread these can get caught a bit every time they pass the burr or whatever. A bobbin being pulled by hand may seem smooth but push and hold the bobbin down into the case and then see if it still pulls smooth and doesn't grab. Next if the tension disk for the bobbin winder is too tight the threads can pull into the other thread and wind on badly but that would be more intermittent i think. Could slip spray have gott on to 1 side of the cone? Bugger of a problem sometimes.Regards Brian

[Wizcrafts]

Here are some things that I have found causing my machines to have variations in the position of the knots in leather. This happens to any and all of my 6 industrial sewing machines.

1. Twisty thread that twists out of the center of the top tension disks
2. Twisty thread that folds over guides and jams the top thread or at least doubles the tension
3. Thread that has twisted out of the thread guide above the spool in the thread stand
4. Thread that is badly wound on the spool. I have some spools with the thread getting caught under the bottom of the windings and it comes off herky jerky. I have other spools with the thread literally unwinding all over the place because of improper bonding and loose windings..
5. Poorly wound bobbins (loose here, tight there, starting stub folded back over the side and back into the bobbin)
6. Thread stubs not clipped close enough to the hole in the bobbin
7. Sharp edges on anti-backlash/ejector springs inside bobbin cases
8. Burrs on bobbin tension spring or shredded thread strands under it
9. Burrs on the hook
10. Totally dry hook that binds slightly in one spot at a certain speed
11. Top and bottom tensions either too loose or too tight for a reliable stitch
12. Dirt, material or thread particles inside the shuttle race
13. Check spring travel too short or tension too light for the weight of the thread
14. Oversize needle hole allowing too much room for error
15. Sticky tape or glue between layers gumming up the needle (try using titanium coated needles and clean them with Goof Off)
16. Hard or soft areas in the leather, caused by tanning inconsistencies. I have actually hit sections of rawhide in some cuts of leather I was using for belts.

[JimRaynor]

3 hours ago, Wizcrafts said:

Here are some things that I have found causing my machines to have variations in the position of the knots in leather. This happens to any and all of my 6 industrial sewing machines.

1. Twisty thread that twists out of the center of the top tension disks
2. Twisty thread that folds over guides and jams the top thread or at least doubles the tension
3. Thread that has twisted out of the thread guide above the spool in the thread stand
4. Thread that is badly wound on the spool. I have some spools with the thread getting caught under the bottom of the windings and it comes off herky jerky. I have other spools with the thread literally unwinding all over the place because of improper bonding and loose windings..
5. Poorly wound bobbins (loose here, tight there, starting stub folded back over the side and back into the bobbin)
6. Thread stubs not clipped close enough to the hole in the bobbin
7. Sharp edges on anti-backlash/ejector springs inside bobbin cases
8. Burrs on bobbin tension spring or shredded thread strands under it
9. Burrs on the hook
10. Totally dry hook that binds slightly in one spot at a certain speed
11. Top and bottom tensions either too loose or too tight for a reliable stitch
12. Dirt, material or thread particles inside the shuttle race
13. Check spring travel too short or tension too light for the weight of the thread
14. Oversize needle hole allowing too much room for error
15. Sticky tape or glue between layers gumming up the needle (try using titanium coated needles and clean them with Goof Off)
16. Hard or soft areas in the leather, caused by tanning inconsistencies. I have actually hit sections of rawhide in some cuts of leather I was using for belts.

I don't know what to say Wiz...

When I was writing the initial post, I was hoping that you'd chime in...
You did, and you made my day!

I'm very sure that the answer lies above.

I'll start with the ones that I find most likely to be applicable to my setup and let you guys know how it works out.

Thanks a lot.

[JimRaynor]

16 hours ago, RockyAussie said:

The picture you have given is a bit short to go by but it looks to me that every 6 to 7 stitches you are having a too tight pull with the bobbin. This could be by the thread cone being a bit offset and going loose as it straightens up every now again. Sometimes when cones get close to finished they can do this a bit also. If you don't have a second bobbin case to try take a picture inside of the case and see if you can see any burring anywhere.(And post it). If the bobbins have a slot for loading the thread these can get caught a bit every time they pass the burr or whatever. A bobbin being pulled by hand may seem smooth but push and hold the bobbin down into the case and then see if it still pulls smooth and doesn't grab. Next if the tension disk for the bobbin winder is too tight the threads can pull into the other thread and wind on badly but that would be more intermittent i think. Could slip spray have gott on to 1 side of the cone? Bugger of a problem sometimes.Regards Brian

Thanks for the solid ideas Brian.

I'll make sure the points you made is checked.

One way or another, this problem will be sorted out this week!