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.