Hook to Needle Distance: A Compromise

[friquant]

How to always have the hook to needle distance be next to nothing?

At first I thought the thread was shredding when I stitched in reverse with long stitch lengths. 

(Thread is Selric brand TEX 135 UNbonded polyester)
(Machine is Jianglong 341 (clone of Juki 341 but with even longer stitch lengths))

On closer inspection, the thread wasn't being torn actually, but in reverse with long stitch lengths (about 8mm) the hook was not catching all three strands of the thread. It might catch one or two.

Here are some photos (recreated) of what it can look like when the hook tries to bisect the thread.
Then I will continue my question in the next message..

Edited June 27 by friquant
grammar

[friquant]

Original question, continued...

I spent some time moving the hook saddle over to reduce the hook to needle distance. The Juki 341 manual says to make the adjustment with the stitch length set to 3mm, but the Juki 341 has a maximum stitch length of 6mm. One could interpret this at least two different ways: A. Set stitch length to 3mm, or B. Set stitch length to half of the maximum. (The Jianglong 341 that I'm actually working on can make 8mm stitches)

Here are photos after my hook to needle adjustment, with stitch length and forward/reverse shown in red text. You will notice that long stitches in reverse prove to give the largest hook-to-needle distance, and I conjecture it was this large hook-to-needle distance that previously had the hook only catching one or two strands of the UNbonded thread.

Since the adjustment, it seems to be doing fine with long stitches in reverse. (Not bisecting the thread anymore.) It makes sense that if you must optimize for either forward or reverse, one would almost always optimize for forward stitching. But here's another avenue I have not used but am considering:

"Set the hook-to-needle distance to zero for long stitches in reverse, and use the hook needle guard to keep the hook from clobbering the needle in all other scenarios."

This might get us down to zero hook-to-needle distance in all scenarios. But we'd also be deflecting the needle (elastic deformation) a little bit on all but the long reverse stitches.

I'd be curious to hear how others have achieved a satisfactory hook-to-needle-distance compromise on machines that can make long stitches in reverse.

Edited June 27 by friquant
Add paragraph about jianglong having longer max stitch length than juki manual

[Constabulary]

You probably have to play with the needle bar height. Have you checked the NB height / needle - hook timing? Procedure should be mentioned in your manual. If it was me I´d probably try lo lower the NB a tiny bit so you will have a bit larger thread loop. But thats just me from a distance. Hard to tell what it going on when not in front of the machine. 

[dikman]

I've had that happen (hook piercing the thread) with a spool of braided thread that I have. In general my machines don't like it and I can't get them to sew consistently, which is a pity as it's nice thread otherwise. It's a very "limp" thread which is the problem I think. Adjusting the hook too close the the scarf in the needle can be risky as it only takes the slightest deflection of the needle to cause a crash.

[Michiel]

I would try too see what’s happening when actualy sewing with tread and material (leather, canvas or what you are using)

It can be hard to see, but if you can, and turn the machine by hand, you can see what is the problem 

if the machine forms a good loop in the thread the hook needle distance is not that important

but if your thread is bad or the timing wrong you might get this.

with some machines you can see it by sewing on the edge of your project and open the slide right of the needle

sometimes you have to look from the underside.

use a flashlight!

[friquant]

In my original post, I reported that after setting the hook-to-needle distance to factory spec it was stitching fine in reverse. Well it's true that the hook is no longer bisecting thread. But it is quite clunky-sounding in reverse with long stitches.

Here is a video that shows where it's still hanging up. 😢
This is stitching in reverse at max stitch length.

 

 

[AlZilla]

19 minutes ago, friquant said:

But it is quite clunky-sounding in reverse with long stitches.

Here is a video that shows where it's still hanging up. 😢

It doesn't seem to be hanging up, really. Just a bit noisy. It's a "clone" of the Juki but with longer stitch lengths, if I recall correctly. Obviously it's not an exact clone, if it has longer stitch lengths. I wonder what they modified to get the longer lengths and if the noise is the price you pay for it?

Really, how often are you going to reverse stitch at maximum stitch length? And probably only 2 or 3 stitches just to backtack.