Very frustrating loss of bobbin tension mid-stitching, help!

[medion]

Hi all,

I'm working on 10 wallets and 3 of them are having the strangest loss of bobbin-tension after rounding the corner. I cannot work out what's going on, and I've re-worked two of them hand-winding through the existing holes, to the same effect. I cannot for the life of me work out why this is happening. It's on a JUKI 1508 NH - any thoughts on what's going on would be so very helpful!

Cheers, Medion.

[Wizcrafts]

The problem could be caused by twisty thread (top and/or bobbin), or a change in the density of the leather as you round the corner, or the glue/tape you baste them with, or the needle point shape, or the foot pressure, or by the setting of the check spring.

Obviously, the tension has changed after turning that corner. Try reversing the direction of the bobbin and adjust the tension to balance the knots. Run a little higher overall tension to make it easier to position the knots.

Try to watch the leather as you round the corner to see if it lifts with the needle. More foot pressure would subdue that problem.

Try a different needle with a different point. A diamond, or triangle point may help.

Use titanium coated needles and keep a dauber and Goof Off handy if you sew through leather tape or heavy cement.

[medion]

2 hours ago, Wizcrafts said:

The problem could be caused by twisty thread (top and/or bobbin), or a change in the density of the leather as you round the corner, or the glue/tape you baste them with, or the needle point shape, or the foot pressure, or by the setting of the check spring.

Obviously, the tension has changed after turning that corner. Try reversing the direction of the bobbin and adjust the tension to balance the knots. Run a little higher overall tension to make it easier to position the knots.

Try to watch the leather as you round the corner to see if it lifts with the needle. More foot pressure would subdue that problem.

Try a different needle with a different point. A diamond, or triangle point may help.

Use titanium coated needles and keep a dauber and Goof Off handy if you sew through leather tape or heavy cement.

Thanks very much for all these ideas - I will try swapping in a new needle to start with and see how I go. With regards to twisting thread, I wonder if the thread is twisting when I round the corner? My corner rounding is done by spinning the wheel by hand, as I cannot reliably control the clutch and round the corner. So, I sew up to the corner, stop, hand crank and turn the corner with the needle down and the foot up. This is how I've always done it, and I've rounded literally hundreds of corners on hundreds of wallets and other objects, but for some insane reason this is now plaguing me... Anyway, let me try a needle change and changing the bobbin direction. Thanks again.

[RockyAussie]

I am thinking that after you lift the presser foot you are at the same time having the tension discs open up which then do not come fully closed as quickly as they should. Try and see if there is something catching the little rods that opens the discs or the rod that pushes the plate that opens them. Might just need a bit of oil.On the other side of the machine check if the parts that push that little rod are not moving as freely as they should as well. If all this gives you no joy....try lifting out your needle until only the tip is in place then only partly lift the presser foot and then do your turn. If you have the needle positioner on your machine you may have to disable it first.

[medion]

17 hours ago, RockyAussie said:

I am thinking that after you lift the presser foot you are at the same time having the tension discs open up which then do not come fully closed as quickly as they should. Try and see if there is something catching the little rods that opens the discs or the rod that pushes the plate that opens them. Might just need a bit of oil.On the other side of the machine check if the parts that push that little rod are not moving as freely as they should as well. If all this gives you no joy....try lifting out your needle until only the tip is in place then only partly lift the presser foot and then do your turn. If you have the needle positioner on your machine you may have to disable it first.

Thanks, I'll take a look! Honestly, I have so many tension issues with this machine, none of my other 3 machines cause me so much drama... I feel like I'm constantly fixing a hangup or battling a bizarre issue like this...

[medion]

This actually looks like it's not an entirely uncommon problem

 

[kgg]

On 6/11/2022 at 2:44 AM, medion said:

It's on a JUKI 1508 NH - any thoughts on what's going on would be so very helpful!

You never mention what size of thread or needle combination you are using. My suggestion to try would be to go up one needle size to give just a little bigger hole size so the thread isn't as tight in the hole. If that doesn't work when you are making the turn and lifting the pressor foot slightly make sure the needle is almost bottomed out before twisting the item.

kgg

[Wizcrafts]

@medion

One thing that hasn't been mentioned is the needle system you are using. Are you using System 190 or 135x16/17? Whichever you were using, have you tried changing the needle bar height and using the other system? I sometimes raise the needle bar on one of my specially modified machines to use system 190 needles and notice some oddities vs system 135x. I attribute some oddities to the longer needles flexing.

One more thought that flashed across my mind is the alignment of the needle's eye. Have you tried altering the rotational alignment slightly? Perhaps the angle that the thread passes through the eye affects the tension on corners as you rotate the work clockwise. I wonder if a slight clockwise rotation of the needle would help?

[Constabulary]

I make a turn when the needle has risen and I leave just the needle tip in the material (needle eye visible) and I lift the foot just enough to give the material free like 2mm above the material so I have no tension release. On my 111G156 I also have adjusted my tension unit the way that it releases very late meaning it only release when the foot lift lever is in its upmost position. That ensures I have no tension release when seeing very thick materials.

If you are using a foot lift pedal make sure your foot does not rest on the pedal.

My 2 cents here.

[medion]

Thank you everyone for your help - so, for future people having this issue, it seems like an increase in needle sized has likely resolved it in tests. I need to run a few actual wallets now, however, with scrap it looks like it's resolved. I'm running M40 thread needle 130/21

Edited June 16, 2022 by medion

[kgg]

8 minutes ago, medion said:

it seems like an increase in needle sized has likely resolved it in tests

A good chart for needle / thread sizing for future reference is: https://www.tolindsewmach.com/thread-chart.html

kgg

[medion]

I'm also noticing something else which is contributing to inconsistency - thread spooling off my thread cones is not smooth. I can feel it jerk, especially as it spools off the bottom, as if there is a minor stickiness factor in the cone thread. Is this a result of a bad batch of thread? Or?

[kgg]

16 minutes ago, medion said:

I'm also noticing something else which is contributing to inconsistency - thread spooling off my thread cones is not smooth. I can feel it jerk, especially as it spools off the bottom, as if there is a minor stickiness factor in the cone thread. Is this a result of a bad batch of thread? Or?

There are number of possible reasons so are:

1. Poor quality of thread and or thread tension on the spool during manufacturing usually found with inexpensive Chinese thread. Use a brand name thread to get consistency.

2. A lot of problems with thread happens with 8 oz spools particularly black color thread. Change spool and or replace with the 1 lb. spools.

3. The distance from the top of the spool of the thread to the guide on the spool holder needs to be at least 2.5 times the height of the spool thread. Adjust spool height.

4. To steep an angle from the guide on the spool holder to the first guide on sewing machine. Preferred angle is as close to horizontal as possible.

A photo of your thread path from the spool of thread to the first guide would be helpful in spotting other possible causes.

kgg