Messed up my machine (juki 441 clone), advice appreciated.

[CowboyBob]

3 hours ago, Ysalex said:

Update: i put the machine back together and I gave cowboybobs Timing method a try instead of the video. I am curious about one thing. My shuttle/hook has a bit of back/forth play, maybe 1-1.5mm. When I align the hook to the needle when the needle is at a 5.5mm rise, so I align it to the backward (counterclockwise) play, or the forward (clockwise) play? If the shuttle/hook should have no play, is there a screw somewhere I can tighten to stop it?
 

Either way, the timing is better. Its bulletproof in forward for sure. 
 

In reverse I still get missed stitches, although now sometimes I can string together 20-30 reverse stitches before a missed stitch. One missed stitch means they all miss after that point. Sometimes it’s only 3-4 reverse stitches before I start skipping, but it’s a definite improvement.

 

on the skipped reverse stitches, I have stopped the machine, opened the front cylinder arm cover, and taken a look at what’s happening.

 

The best I can tell, the thread develops a twist, sort of a counter twist. Like if you held a piece of thread between your thumb and index finger in both hands and twisted the thread in opposite directions until the thread opened up into its three different strands. When this happens the loop forming, the loop that the hook will grab, twists away from the path of the hook. the hook misses, and then I start to miss stitches. Sometimes it will catch 1 or 2 of the strands, which causes the thread to separate and rip on the bobbin shuttle.
 

I know nothing about these machines, but I have three theories that are all probably wrong:

1: Tension.

I have tried a lot of thread tension settings. Right now, using 207 nylon bonded thread, the thread is just loose enough on the bobbin and the main thread that I can pull the leather away from the machine with a mild pull. I get stitches in the middle, no knots or loops visible or happening on either side. that said, I don’t know how sensitive these machines are to tension. If the tension is bad, maybe it’s causing the thread to unravel on reverse stitches when the loop for the hook is being formed. 

 

2: The hook distance from the needle.

If I am not mistaken, there is an adjustment for how far the hook is from the needle. If my hook was closer, even when the thread twisted, the thread loop might still catch. The distance right now between the hook and needle is really small, but maybe this distance is very finicky.

 

3: The thread.

The thread I have is of an indeterminate age, since I got it with the machine. For sure it’s 1+ year old, but could and probably is a bit older. Does bonded nylon thread have a shelf life? Would old thread be causing that kind of issue?  I have also noticed quite a bit of either wax residue or thread fiber building up on the various loops and eyes along the thread channel, I’m not sure if this is an indication of anything.

 

 

 

Ok, put  your stitch length on zero so the feed dogs aren't moving & measure the distance from the needle plate opening to the feed dog on both the front & back they need to the same distance.Look @ the hook position on page #2.In this manual.Note to everyone NEVER USE CAM ON TOP FOR HOOK TIMING!

 

441 Engineers manual.pdf

Edited August 4, 2020 by CowboyBob

[Ysalex]

10 hours ago, CowboyBob said:

Ok, put  your stitch length on zero so the feed dogs aren't moving & measure the distance from the needle plate opening to the feed dog on both the front & back they need to the same distance.Look @ the hook position on page #2.In this manual.Note to everyone NEVER USE CAM ON TOP FOR HOOK TIMING!

 

441 Engineers manual.pdf

Thanks cowboyBob. 

I followed these instructions and yours for timing to a T, and now it fails to pick up any stitches in reverse or forward. The thread very reliably twists away from the hook.

[RockyAussie]

24 minutes ago, Ysalex said:

Thanks cowboyBob. 

I followed these instructions and yours for timing to a T, and now it fails to pick up any stitches in reverse or forward. The thread very reliably twists away from the hook.

A close up picture of the needle just entering the leather might help here. What type of needle is it and have you tried replacing the needle yet with a new one?

[Ysalex]

21 minutes ago, RockyAussie said:

A close up picture of the needle just entering the leather might help here. What type of needle is it and have you tried replacing the needle yet with a new one?

yeah, I've tried a couple different ones just to be sure. Thanks for your help BTW, its really appreciated.

[DonInReno]

....well, if you give up on it and want to go with a new machine let me know and we could come up with a price that works for us both.   

[Wizcrafts]

6 hours ago, Ysalex said:

Thanks cowboyBob. 

I followed these instructions and yours for timing to a T, and now it fails to pick up any stitches in reverse or forward. The thread very reliably twists away from the hook.

Apparently, your thread is overly twisty. When I have twisty thread it usually twist clockwise. So, I counter it by threading through to holes in the top post in a counterclockwise direction. If your machine doesn't have a post with two or more holes, wrap the top thread CCW around something along the path. This should counteract the twist and give you enough loop for the hook to pick off.

If this is the case, replace the thread ASAP.

[Ysalex]

Update:

 

thank you everyone for the advice. I was (actually, my wife was) able to find a professional sewing machine repair guy in our city. After trying to work around it the stick screw it became necessary to remove it.

 

after working the day with a carbide drill bit, a lot of patience and various extractors, it came free! 
 

so now I need to replace the screw with the same length and thread size. Not to keep blasting the forum with questions but does anyone know where I can find that info?

after I get it replaced hopefully it’s just a matter of timing and adjustment. I also ordered brand new needles just to be sure, and new bonded nylon thread. 

 

 

Edited August 10, 2020 by Ysalex

[JJN]

Yay! That has to feel good getting that thing out of there. If you have a micrometer or good caliper, measure the diameter across the threads to the nearest thousands of an inch. Then measure along the length 10 threads, peak to peak also to the nearest thousands of an inch. Post those measurements and we can figure it out. The screw could be metric or is could be fractional inch. Most likely is not a screw you can get locally. If you have a parts manual, look it up and google the part number.

You did a good job extracting that screw without causing any damage. Wipe all the metal shaving out of the machine!

[chrisash]

Company details on this link, give them a ring and photo of where it was in the machine to avoid confusion

https://artisansew.com/leatherstitchingmachine.html

[dikman]

Or you could contact Cowboy Bob and ask him. I recently had reason to check the size of the screws holding the bobbin winder plate on and was very surprised to find they're not metric. They're not Whitworth or BA, my best guess is 3/16" UNF.

[CowboyBob]

It is a 15/64" x 40tpi

[dikman]

I'm really surprised at this, I know all about the older machines having oddball screw/thread sizes but I just assumed that when the Chinese copied the machines they would have used standard, probably metric, threads. Who'd have guessed......

[Ysalex]

Thanks guys, and thank you cowboy bob, that seemed to be it.

 

i couldn’t find that screw near me so I ordered one from Chester at artisan in north California, it’s near to me and they are pretty quick to ship so it should be here soon.

in the meantime I am happy to say that the machine is now timed properly and bulletproof (as far as I can tell) in reverse and forward. I found a sewing machine mechanic in my area and he helped me tonight get it working. 
 

the only challenge past the missing set screw was that even with the set screw removed, and the other two screws loosed/removed, that shaft did not want to turn at all. It took awhile and a lot of gentle nudging/pressure, and some heat, to work it loose. After that it was easy sailing.

 

im pretty sure that whoever owned this machine before did that adjustment themselves and did a poor job of it. I also think they used too strong a strength of lock-tight and some got into the shaft. 
 

last thing I’ll need to work out tomorrow is that the presser feet are not feeding the material through correctly. I get some forward motion and then I get a near equal amount of back motion, so the stitch length is very short even with the handle dialed all the way up or all the way down.

 

but I’m not going to sew with it until I get that set screw to lock the shaft in place. 

20 hours ago, dikman said:

Or you could contact Cowboy Bob and ask him. I recently had reason to check the size of the screws holding the bobbin winder plate on and was very surprised to find they're not metric. They're not Whitworth or BA, my best guess is 3/16" UNF.

Yeah that surprised me too.

[dikman]

Sometimes I am so dumb (something to do with getting old, maybe?), anyway I had cause to adjust the feet on my 4500 so got out the "manual" that came with it. Wasn't any help BUT the parts list is very comprehensive, listing all the screws used, and they're all what I would call American thread sizes, fine pitch.

No metric, which still surprises me.

[CowboyBob]

6 hours ago, dikman said:

Sometimes I am so dumb (something to do with getting old, maybe?), anyway I had cause to adjust the feet on my 4500 so got out the "manual" that came with it. Wasn't any help BUT the parts list is very comprehensive, listing all the screws used, and they're all what I would call American thread sizes, fine pitch.

No metric, which still surprises me.

And you wonder why did a Japanese company design it that way?Which is nice since they are more in common with alot of the Singer screws.

[dikman]

Nice for you, but fine-thread US screws are not that common here, unfortunately. I remember when I was working on one of my black powder guns I had to order in a specific tap from Track of the Wolf because it wasn't available here. I guess that's what I get for living in the "other" colonies.