Play hide the knot?

[sportycliff]

Good Morning Good people!

 

I have a Mitsubishi CU-865 cylinder arm that I've been fussing with for a little while. (factory servo with box style reducer via Toledo)

Lately I tend to make bags, but was hoping that it would help with some other work as well.

My first question, SHOULD this machine be capable of tensioning the thread (138) well enough

to properly sew two layers of 6 oz veg? As of now it won't...I'll stop here. Snagged this photo from another post just for reference.

 

Thanks...Cliff

Edited January 30, 2023 by sportycliff
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[DonInReno]

If the upper tension regulator won’t provide enough tension even when adjusted as tight as it will go, there’s a good chance the tension release is improperly adjusted not allowing the tension disks to fully engage the thread.

Thats assuming the lower thread tension is correct, and the needle size is large enough to allow the know to be pulled up.

[sportycliff]

14 minutes ago, DonInReno said:

If the upper tension regulator won’t provide enough tension even when adjusted as tight as it will go, there’s a good chance the tension release is improperly adjusted not allowing the tension disks to fully engage the thread.

Thats assuming the lower thread tension is correct, and the needle size is large enough to allow the know to be pulled up.

#1 Checked and OK

#2 Bobbin tension OK, tried needles up to two size larger than called for (24)

[DonInReno]

I’m betting #1 is still your problem.   It’s very hard to just look at the tension disks and tell if the tension release is preventing the last few .001” of disk pressure.   I’d also check for deep grooves in the tension disks that might be preventing them from firmly gripping the thread.    Perhaps the tension adjusting nut is bottoming out on something?   Aftermarket tensioners are so poorly made, if it’s ever been changed any number of things could be wrong.

Have you had the tensioner apart lately?   Is the machine new to you?  Do you have a picture showing how it’s threaded?   Is the thread down between the disks and not ridding up on the outside edges?

If you can physically pull thread through that tensioner with bare hands when it’s tightened fully, it’s definitely something in there.

 

[sportycliff]

49 minutes ago, DonInReno said:

I’m betting #1 is still your problem.   It’s very hard to just look at the tension disks and tell if the tension release is preventing the last few .001” of disk pressure.   I’d also check for deep grooves in the tension disks that might be preventing them from firmly gripping the thread.    Perhaps the tension adjusting nut is bottoming out on something?   Aftermarket tensioners are so poorly made, if it’s ever been changed any number of things could be wrong.

Have you had the tensioner apart lately?   Is the machine new to you?  Do you have a picture showing how it’s threaded?   Is the thread down between the disks and not ridding up on the outside edges?

If you can physically pull thread through that tensioner with bare hands when it’s tightened fully, it’s definitely something in there.

 

With the foot down there is a gap between the actuating rod and the rearmost disc, no contact.

Had tensioner art several times, perhaps minor scuffing on the plating, but no discernable wear. 

New machine yes, but not new to machines. It's threaded properly and you cannot pull thread when engaged.

[sportycliff]

Bottom thread full tension...2 layers 2.3 mm

[sportycliff]

Top...

[Wizcrafts]

Try to cop a boo at the thread as it goes around the bobbin case and comes up to see if it is snagging on something. Also, check the hook timing to see if it is retarded and too close to the eye. If it is close, advance the timing a bit so the hook is about 1/16 inch above the eye at pickoff time. Also, make sure the hook isn't hitting the needle and that the needle easily clears the hole in the feed dog..

Q: Are you using a leather point or round point needle?

[sportycliff]

30 minutes ago, Wizcrafts said:

Try to cop a boo at the thread as it goes around the bobbin case and comes up to see if it is snagging on something. Also, check the hook timing to see if it is retarded and too close to the eye. If it is close, advance the timing a bit so the hook is about 1/16 inch above the eye at pickoff time. Also, make sure the hook isn't hitting the needle and that the needle easily clears the hole in the feed dog..

Q: Are you using a leather point or round point needle?

Leatherpoint, brand new. I will chk the timing.

 

[DonInReno]

Those are definitely twists in the thread or the thread is untwisting as it forms the knot - not a tension issue.   Sorry to drag you through all the tension stuff - I should have asked for a picture.   
 

What brand and type of thread is it?   To be honest, if I don’t know anything about the bottom problems I’d still think your thread doesn’t look right on top - like it’s not bonded and a loose twist - not the normal dense bonded nylon we usually use.   The good news is, a different spool of thread will probably solve the issue.

I’ve attached a random picture of 138 size thread - look at how twisted your top thread is compared to how it lays down flat in the pic.

Edited January 30, 2023 by DonInReno

[sportycliff]

3 hours ago, Wizcrafts said:

Try to cop a boo at the thread as it goes around the bobbin case and comes up to see if it is snagging on something. Also, check the hook timing to see if it is retarded and too close to the eye. If it is close, advance the timing a bit so the hook is about 1/16 inch above the eye at pickoff time. Also, make sure the hook isn't hitting the needle and that the needle easily clears the hole in the feed dog..

Q: Are you using a leather point or round point needle?

 

8 minutes ago, DonInReno said:

Those are definitely twists in the thread or the thread is untwisting as it forms the knot - not a tension issue.   Sorry to drag you through all the tension stuff - I should have asked for a picture.   
 

What brand and type of thread is it?   To be honest, if I don’t know anything about the bottom problems I’d still think your thread doesn’t look right on top - like it’s not bonded and a loose twist - not the normal dense bonded nylon we usually use.   The good news is, a different spool of thread will probably solve the issue.

I’ve attached a random picture of 138 size thread - look at how twisted your top thread is compared to how it lays down flat in the pic.

While I guess anything's possible, it sews perfectly on my other machine, and on lighter bag leathers. I'll swap it out with something different first thing.

I think @wiz may be onto something with the timing. I've changed the timing twice since he posted and had worse results, and slightly better results. I'll try again tomorrow as my arthritis is telling me it's time to quit. 

I also receive a new tensioner in the mail today, I'll put the timing back to where it was and try that tomorrow just to rule it out, then go back to the timing...will post back.

[DonInReno]

There are definitely some skipped stitches on the bottom side, so that may be another issue.

it sounds like you’ve had one heck of a day chasing this thing around - you’re really close to getting it, so tomorrow should be a good day

[sportycliff]

17 hours ago, DonInReno said:

There are definitely some skipped stitches on the bottom side, so that may be another issue.

it sounds like you’ve had one heck of a day chasing this thing around - you’re really close to getting it, so tomorrow should be a good day

Not a better day at all.

Replaced tensioning system, and adjusted

Re-timed hook to factory specs Needle bar 2.4 mm up from bottom .5 mm needle gap, 1-1.5 mm above eye

Best I can do on ONE layer of 2.4 mm veg tan...Knots on top And occasional loops on bottom, and a crappy stitch.

 

Edited January 31, 2023 by sportycliff
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[sportycliff]

 

Edited January 31, 2023 by sportycliff

[sportycliff]

Ok, just noticed this, not sure if it's relevant.

The guy who owned this before me apparently ground the teeth down to almost nothing on the feed dog.

I just noticed it was at and/or below the surface of the plate.

That may explain the crappy stitching, but would it cause the looping? I tried maxing both foot pressures, and it doesn't change anything...

The feet on the machine are smooth, so my guess is that the only thing feeding is the needle. I tried my serrated outside foot from my other machine, maybe a lttle more  consistent stitch(?) Maybe wishful thinking. I've ordered a binding set but it's smooth, and apparently the only style on ebay or amazon. Anyone know where to get a serrated dog for one of these?

[kgg]

On 1/30/2023 at 11:46 AM, sportycliff said:

My first question, SHOULD this machine be capable of tensioning the thread (138) well enough

If I'm not mistaken this machine has the same capabilities as the PFAFF 335 and similar clone machines. Most of the 335 machines are really only capable of sewing with V92.

 

41 minutes ago, sportycliff said:

I just noticed it was at and/or below the surface of the plate.

This machine was probably setup to sew fabric and aggressive teeth may have been damaging the material.

kgg

 

[sportycliff]

Any other thoughts?

[Burkhardt]

16 hours ago, sportycliff said:

Any other thoughts?

Now you're sewing on a single piece of leather that might not be thick enough to hide the knot. Another thing I see is how the top stitches have a descent stitch length but are tight on the bottom. How firm is the leather you're using? Does the leather lift at all off the arm when stitching?

[Constabulary]

I still would assume you need a larger needle or a thinner bottom thread and / or try a heavier beehive spring on the tension unit. If the former owner sewed fabric then the spring may be too weak.

This is from College Sewing in the UK but you will find them on your end as well:

https://www.college-sewing.co.uk/b3114-232-000-beehive-spring-heavy-juki-genuine.html

When you haven lowered the foot on the material do the tension discs feel kinda loose or wiggly?

Edited February 2, 2023 by Constabulary

[sportycliff]

6 hours ago, Burkhardt said:

Now you're sewing on a single piece of leather that might not be thick enough to hide the knot. Another thing I see is how the top stitches have a descent stitch length but are tight on the bottom. How firm is the leather you're using? Does the leather lift at all off the arm when stitching?

I've got both feet maxed out...doesn't seem to lift at all.

57 minutes ago, Constabulary said:

I still would assume you need a larger needle or a thinner bottom thread and / or try a heavier beehive spring on the tension unit. If the former owner sewed fabric then the spring may be too weak.

This is from College Sewing in the UK but you will find them on your end as well:

https://www.college-sewing.co.uk/b3114-232-000-beehive-spring-heavy-juki-genuine.html

When you haven lowered the foot on the material do the tension discs feel kinda loose or wiggly?

I'm looking into adding a pre-tensioner, I didn't realize heavier duty springs were available too, I'll look for both. Thanks.

 

[sportycliff]

On 1/31/2023 at 12:27 PM, kgg said:

If I'm not mistaken this machine has the same capabilities as the PFAFF 335 and similar clone machines. Most of the 335 machines are really only capable of sewing with V92.

 

It shares the same bobbin case, bobbins,  and looks like the same hook as my Sailrite Fabricator.

That machine has zero problems with 138, nothing is shredding, so I assume clearances are ok, I'm going to try adding a pre-tensioner.

 

 

 

[kgg]

1 hour ago, sportycliff said:

I'm going to try adding a pre-tensioner.

To add a bit more tension to the top thread try:

i) top thread entering through the top hole of the post guide wrap it around to the back side and out the bottom hole in the post guide located on the top of the machine

ii) top thread through the first hole in the vertical guide located on the main tensioner wrap it around and out the second hole and then onto the underside of the little guide pin.

kgg

[DonInReno]

On 2/1/2023 at 4:17 AM, sportycliff said:

Any other thoughts?

I’m out of ideas - it appears that there is roughly enough top tension to mostly pull the knot up, but that lower thread looks crazy and appears to have varying amounts of tension.   I’d guess it’s partially whatever brand and type of thread and partially something underneath it’s hanging up on giving the inconsistent bottom tension.

The finger that keeps the bobbin case in alignment has to have enough clearance for thicker thread to pass around easily.  There is no bobbin case opener to adjust, but clearance is adjusted with careful metal removal and polishing.

If this machine was made to only sew thinner thread, in addition to a tight area at the bobbin alignment notch, there may also be resistance from a tight spot somewhere else around the bobbin case that would have to be clearanced.

Thats about all I’ve got.

 

 

 

 

[sportycliff]

9 hours ago, DonInReno said:

I’m out of ideas - it appears that there is roughly enough top tension to mostly pull the knot up, but that lower thread looks crazy and appears to have varying amounts of tension.   I’d guess it’s partially whatever brand and type of thread and partially something underneath it’s hanging up on giving the inconsistent bottom tension.

The finger that keeps the bobbin case in alignment has to have enough clearance for thicker thread to pass around easily.  There is no bobbin case opener to adjust, but clearance is adjusted with careful metal removal and polishing.

If this machine was made to only sew thinner thread, in addition to a tight area at the bobbin alignment notch, there may also be resistance from a tight spot somewhere else around the bobbin case that would have to be clearanced.

Thats about all I’ve got.

 

I've tried two different types of bonded nylon. Both run fine on my other machine.

 

Number 24 has a finger on the bottom side which fits a notch in the hook assembly

which stops the center section of the hook from spinning, is that what you mean?

I don't mind a little mod work, just want to mod the correct items.

 

9 hours ago, DonInReno said:

 

 

[Constabulary]

maybe its just the hook that is a bit close to the needle so the gap between hook notch and position finger is too tight. You can move the hook a tiny bit (maybe 0.5mm or so) to the right (if not already flush with the machine arm) by loosening the 2 or 3 set screws on the hook body. Better check the needle hook timing after doing this.