Juki LU-563 chrome tan and inconsistent tension

[Willbury]

Hello, looking for a bit of advice.

I've been having an ongoing stitch consitancy issue while sewing two to three layers of approx 5 oz chrome tan leather.    Approximately once in a ten inch length it's common for me to have one stitch not pull up into the material.   See attached picture.

Adding tension does negate the issue sometimes, but it usually comes back.

I've noticed that the diamond point needles I'm using also tend to develop burrs on the cutting edges relatively fast and I had assumed the leather density was causing it  but wonder if there is something else I might be missing?   It doesn't happen when sewing veg tan of the same weight and thicknesses.

is it common to burn through needles with chrome tan leather? Would the burrs cause my problem?

The set-up I'm using is as follows:

juki lu-563

Schmetz 135x16  size 24 diamond point needle

135 nylon thread (not lubricated)

 

 

 

These are the needles I've been using.

[Uwe]

A needle will generally last quite a long time in a well-adjusted machine and without abuse. If your needle develop burrs it usually means it's touching something it shouldn't. The needle may get deflected by lumps in the material, or by a snagged thread pulling the needle sideways. Does you feed dog hole look all jagged around the edge?

Chances are that your needle burrs and thread snags are caused by the same or a related problem. I suspect your top thread occasionally snags somewhere as it wraps around the hook or elsewhere in the thread path. Verify your hook timing is spot-on. Make sure the needle guard actually does its job of protecting the needle. If you recently installed new throat plate or feed dog, make sure they are burr free. Inspect your thread/hook action as you make a few very slow turn by hands with the hook cover slide removed. Is the bobbin case opener pulling the bobbin case back enough for the thread to slip through the gap easily, and then get out of the way quickly enough to let the thread pass?

 Here's a video snippet of how the thread should wrap around the hook and how the bobbin case opener should operate on a well-adjusted LU-563 class machine (on my machine the timing belt synchronization had been off before):

Here's a short video on how the needle guard should be adjusted:

 

Edited July 18, 2017 by Uwe

[Willbury]

Thanks for the suggestions, after having another quick look at the machine I wonder if bobbin case opener is causing a slight hang-up  when releasing the thread.  

Timing seems fine and the needle guard does seem to be in the correct position to deflect the needle.  I'm going to check this one more time, just to make sure.

The funny thing with the needle burring is that it happens on both of the sharp edges of the point (closest and furthest from the machine operator) which makes me question weather it's the material causing it to happen, especially since there's no indication of the needle striking anything on the machine.    If it is striking the machine I would expect to only see it on one edge of the needle point.    Could these be a bad batch of needles?

I'm going to try adjusting that bobbin case opener and see what happens.  I'll report back.

Thanks again.

Will

 

[Gregg From Keystone Sewing]

NM180/24 is a thick blade, and I'm guessing that the either the hook, needle guard, or both, need to be adjusted.

See attached, this should help.

LU-1500N Engineers Manual_Hook.pdf

[Willbury]

Thanks for posting that, very helpful to have on hand.

I had adjusted the inner hook guide arm clearance after Uwe's post and I haven't had the stitch issue since.  We'll see if it recurs in the next few days (hopefully not) if it does I'll go back and do a complete assessment of all the adjustments again.

[Willbury]

I thought I'd post back up on this issue I was having.  

The inconsistency reared it's ugly head again today when going back and sewing chrome tan with the LU563.  I then spent hours and tore into the machine and made sure everything was set-up properly and at the end everything seemed fine except the lower stitch once and a while won't pull up into the leather.  Even with the top tension near maximum and the bobbin tension as low as it will go.

Next I went over and tried sewing on my Singer 211 with the same thread and same leather.  Immediately I had to increase the upper thread tension close to maximum and it two was displaying the irregular thread tension on the underside even with the top tension so high.

I've come to the conclusion that the issue must be the leather density and the top finish on this pretty basic chrome tan leather.  I've been sewing with both topsides facing out and I think it's preventing the thread pulling up properly from the underside.

Neither machine has a problem sewing veg tan in the same thickness or thicker and you don't need to run the unreasonable thread tensions to make it work well.

I guess I'll have to use a bigger machine.  I quickly tried out my Adler 205 which is set-up with 305 thread and it did the job no problem.  I wonder if I downsize the needle and thread if it will still work....

 

 

[RockyAussie]

6 hours ago, Willbury said:

at the end everything seemed fine except the lower stitch once and a while won't pull up into the leather.

That sounds like you don't have enough foot pressure down. If the leather lifts a bit the knot will be on the bottom. Some thread lubrication can help as well. A smaller needle size can help consistency as well sometimes probably because the leather is less likely to lift. Regards Brian

[Willbury]

Interesting thought, I'll experiment with foot pressure. 

I did some additional experimentation last night and went down to a #22 needle with the same results.  

Then decided to try some 69 thread with the #22 set-up, so a very oversized needle. After substantially reducing the upper thread tension, since I was no longer using the 135, the stitching was perfect...   

My hunch is still leaning towards the leather as the culprit. I'm thinking  the hole cut by the needle closes somewhat during the needle upstroke and makes it difficult to pull the knot up into the leather.  A bigger needle to thread ratio may solve the problem, but since a #24 needle is not enough and already really over the machine capacity I may be out of luck.  

I will try the presser foot pressure to see what happens....

 

[Wizcrafts]

Your hypothesis is correct Willbury. The hole is healing on the bottom as the needle ascends. Try a diamond point needle and see if you get a better outcome. Titanium needles may help too.

[Willbury]

The needles I've been using are actually diamond point.

One of the other problems I'm encountering with this leather is that the trailing and leading edges of the needle blade are actually developing burrs on them.  I wasn't aware of Titanium needles, I would imagine it would prevent that problem, but I'm unsure if it help the knot pulling up.    Unless there are some options for different diamond point profiles that would do a better job making that hole bigger?