Thread guide Adjustment & function

[brmax]

Im looking for some clues on how this particular thread guide plays a role. Adjustment of this guide is up or down and can be turned and mounted upside down. 

This is on Juki 1341, 1541 several 1500 series and I have seen it on some other brands including Consew

https://www.sewingpartsonline.com/thread-guide-juki-21355805.aspx

in the below pic, item 9 is the location  

 

 

Thanks for your help, its appreciated

Floyd

Edited August 16, 2018 by brmax

[Uwe]

I believe your #9 part just looks like and is called a thread guide, but is really an around-the-hook thread tension regulator. With the thread take-up lever in the bottom-most position, the regulator #9 allows a very subtle adjustment of exactly how much slack or tension the thread has as it is wrapped around the farthest part of the hook.

Too much tension: thread snaps around the hook and may cause more thread to pull from the spool when it shouldn't.

Too little tension: thread is not taught enough to nicely pull through the gap between the bobbin case tab and throat plate cutout at the right moment, potentially causing a snag that pulls more thread from the spool when it shouldn't.

Just right tension: thread consistently and smoothly pulls through the gap at exactly the right time.

The Durkopp Adler 867 has a similar device, except it is adjusted horizontally. It essentially has the same function as your #9 part:

The DA service manual simply states to observe the thread getting wrapped around the hook, and to adjust the red regulator until it's just right.

On older machines that do not have this regulator, the bottom position of the thread take-up lever alone (and relative timing with hook rotation) determines how taught the thread is when it wraps around the hook. I remember topics where the thread take-up lever seemingly arrives at the very bottom a wee bit too early or too late. This regulator eliminates that potential problem. The regulator allows more freedom to adjust the around-the-hook thread tension somewhat independently of the thread take-up lever timing.

Anyways, that's my theory.

Edited August 16, 2018 by Uwe

[brmax]

Uwe: I want to thank you for this explanation.

This thread guide has been an interest for awhile. These professional tips and design facts you have provided about this part with its adjustment features are great!

In my machines future adjustments I can now work on in the days ahead, and certainly have an understanding how to better set this thread guide.

 

Really appreciate the help, and

Have a great day

 

Floyd

[Gregg From Keystone Sewing]

It's funny, I too have longed for a detailed explanation, and I even went as far as contacting Durkopp Adler, as they have this regulator with numbers on them for index.  I didn't get much.  This page has the most detailed information I could find for any type machine that has this adjustment, and I've looked everywhere.

See attached.

DurkoppAdler867Instruction_Pages.pdf

[Uwe]

So it appears the check spring then really performs two distinct functions on machines with a thread regulator:

1. Keep thread taught while the needle is above the material to prevent the needle from accidentally piercing the thread on the way down

2. Apply very slight tension to the thread as it wraps around the farthest part of the hook

The thread regulator device allows you to make sure the second function is indeed happening.

Normally, you adjust the check spring resting ledge so that the check spring hits that ledge just as the needle enters the material. Then you can use the thread regulator to make sure the check spring just barely lifts off that ledge as the threads wraps around the farthest part of the hook.

You learn something new every day. I'll have to check that out on a real machine when I get a chance. 

[gottaknow]

On 8/17/2018 at 6:43 AM, Gregg From Keystone Sewing said:

It's funny, I too have longed for a detailed explanation, and I even went as far as contacting Durkopp Adler, as they have this regulator with numbers on them for index.  I didn't get much.  This page has the most detailed information I could find for any type machine that has this adjustment, and I've looked everywhere.

See attached.

DurkoppAdler867Instruction_Pages.pdf

Hey Greg, 

Think of that component like a take-up adjustment on a chain stitch machine. If you want to measure the difference in thread pull off, you can thread something you can mark with a Sharpie, (like white thread). Sew on some material stopping with take up lever at the top with the needle up. Mark the thread where it comes through the first thread guide, and again at the eye of the needle. Cut and pull the marked portion of thread out of the machine, rethread and sew after adjusting whatever guide you want to the opposite position. Repeat the sewing, marking of the thread etc., then lay the two marked samples side by side. 

I do this on chainstitch machines to see which adjustments do the most, and which ones are more or less just guides. On lockstitch machines, you may see no difference at all, or some differences. As a general rule, I always set adjustable guides in the middle of their travel and seldom move them after that. It’s not an adjustment that requires much fuss, the check spring travel and stiffness, needle tension, are much more critical. 

It’s kinda interesting to do that test, some machines don’t change in the least, others just slightly, few make a bigger difference. What’s interesting, is look at some old Singer machines and you’ll find no adjustment at all. I suspect Singer made their take up levers exactly the right length and with the correct amount of travel. 

Regards, Eric

[Gregg From Keystone Sewing]

Great stuff as always from gottaknow and Uwe.

gottaknow has a more real world who would bother to think of this and let's just keep going and this is very correct.  This is not the type of adjustment that most mechanics or repair people want to sit around thinking about.  There's usually better things to do in a factory setting.  

When they put numbers on an adjustable guide, I wanted to find out what they were about.  Actually what I attached above was recently new to me, I didn't have anything like it on hand.  

Edited August 19, 2018 by Gregg From Keystone Sewing