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Problem With Tension


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#1 8thsinner

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Posted 01 September 2011 - 03:05 PM

I just picked up a jones model 574, looks something like below but I think my question is generalised.
With two layers of sofa leather hair to hair side it stitches no problem, for two layers flesh to flesh the bottom side when finished feels rough and the loops are sticking out.
Obviously a bobbin issue, and everything is tightened out, I tried adjusting both variably but can't get a good result.
Picture
Is there normally a way inside the machine to reset tension strength or something?
I know nearly nothing about fiddling with sewing machines...

Edited by 8thsinner, 01 September 2011 - 03:06 PM.

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#2 wolfe9

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Posted 01 September 2011 - 06:38 PM

You might get better answers if you post pics of the stitches that you are having problems with , otherwise people are just guessing ..
Good luck

#3 8thsinner

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Posted 01 September 2011 - 07:38 PM

It's just a straight stitch and looks like the lower right image...

http://www.threadsma...-tension-03.jpg

Edited by 8thsinner, 01 September 2011 - 07:39 PM.

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#4 dbusarow

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Posted 01 September 2011 - 08:31 PM

The picture shows not enough top thread tension. I guess it could be WAY to much bobbin tension but based on my Cobra's bobbin tension vs its top tension the bobbin can't get that tight unless somethings broken. You need to tighten up the top. My top tension is typically set so that I have to release the top tensioner to remove the item being sewed from under the foot. I'd break the needle before I pulled any thread loose without doing that.

Dan

#5 8thsinner

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Posted 01 September 2011 - 08:36 PM

I checked through every thing from scratch again, the top thread wasn't actually between the tensioning disks properly, thats why it wasn't adjusting when I changed it.
Problem solved.
Yay. Project now finished.
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#6 wolfe9

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Posted 02 September 2011 - 08:21 AM

Good to hear ..

#7 RFMarsh

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Posted 15 September 2011 - 11:05 AM

The picture shows not enough top thread tension. I guess it could be WAY to much bobbin tension but based on my Cobra's bobbin tension vs its top tension the bobbin can't get that tight unless somethings broken. You need to tighten up the top. My top tension is typically set so that I have to release the top tensioner to remove the item being sewed from under the foot. I'd break the needle before I pulled any thread loose without doing that.

Dan



I just got my Cobra Class 4 and am struggling to figure out the tensioning combinations. I have played around enough to get a good looking stitch on a single layer of 8/9 oz. but then, when I change anything (e.g. going to two layers, switching to a firmer leather of the same thickness), the stitch is horrible. Is there a tutorial on setting stitch tension on the CC4 somewhere?

#8 dbusarow

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Posted 15 September 2011 - 01:57 PM

No tutorial that I know of.

If it's any consolation it took me quite a while to get the tension figured out too. I just thought I was stupid...

Pick what you sew the most, e.g. 2 layers of 8/9 veg tan. Work the tension out on those. Steve mentions in his English manual that you need both the top tensioner and the one on the side to be syncronized. I forget the phrase he uses but something about always adjusting both at the same time.

Once you get them both in the ball park, and it was just a lot of trial and error for me, stick to that sentence. Adjust them both at the same time. I find that the lower one on the side takes smaller adjustments but if you are tightening, tighten both. If you are loosening, loosen both.

You'll eventually get it and once you do even making huge changes in the leather (going to say 3 layers of 16 oz from your 2 layers of 8 oz) only require a little bit of adjusting.

To give you a ballpark to start in, mine are showing about 6 threads of the top adjuster's bolt and about 2 threads on the one on the side.

Good luck!

Dan

#9 dirtclod

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Posted 15 September 2011 - 02:15 PM

I don't have a Cobra but the same style machine i was told to sew on a couple pieces of chap leather till the stitches looked right and they would work fine for just about every other thickness. So far that has worked. Good luck.
I'm old enough to know that i don't know everything.

#10 leatherkind

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Posted 18 September 2011 - 10:31 PM

I had so mach fun trying to figure out correct tension...
It seems to be more difficult to adjust with thin soft leather then with thick and stiff.
For example i was stitching the zippers to soft leather and you can tell that the leather side looks shrunk compare to the zipper.
I guess the tension was too high.
Unfortunately I could not find anywhere numerical specifications on what the tension should be. At best it is "a little more" or "too much" so i had to guess.
Maybe i just did not look in the right place? Please let me know if you have it.
I also realize that if you try to make a complete chart that is probably going to be enormous.
Just imagine now many different tension mechanisms are out there, how many different threads and coatings, and how many different materials...

Nevertheless, one problem at a time.
Here is my example of thread tension. I would greatly appreciate if you tell me if I have it correct or not.
I measured the thread tension by pulling the thread to the back of Cowboy 4500 with luggage scale.
The leather is 1,2 , and 3 layers of 2mm (3/32") oil tan which is not very soft. All together they are about 1/4".
In all three stitch samples the top thread is at constant tension of 1800g (4lb).
The bottom tension is changing three times 200g (7oz), 850g(1lb 14oz), and 2kg (4lb 8oz).
Thread is bonded Nylon #346 (about 1mm in diameter) made by Linhanyl and the needle is #25 leather point.
I have circled obviously bad spots with red (horror) and yellow (outrageous).

As you can see there is little difference for thick material but not so for thin.
I would like to mention that to change the bottom tension so much i had to turn the bolt only 1/2 of a turn.

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#11 CowboyBob

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Posted 19 September 2011 - 03:58 AM

I think your biggest problem is trying to use to 346 to sew so thin,you should try 138 or maybe 207 on the thinner leather.Your leather has to be thick enough for the threads to cross in the center.
Bob

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#12 leatherkind

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Posted 19 September 2011 - 07:40 PM

I think your biggest problem is trying to use to 346 to sew so thin,you should try 138 or maybe 207 on the thinner leather.Your leather has to be thick enough for the threads to cross in the center.
Bob

Thank you Bob very much for your expertise! Considering the high quality of this machine and my inexperience I knew I am doing something wrong.
Can you please also comment on the tension. 4 lbs on top thread isn't it a bit too much? (assuming i am working with thicker stuff)
Although I was not able to set it to much less then that because the bottom thread is getting almost free of tension.

Thank you again for your time.

#13 Cath79

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Posted 18 January 2012 - 09:24 PM

I am having mega problems getting proper tension my cobra. It's been months of hours, trying and giving up. Going back to hand sewing and my old crappy machine. I am worn out, and confused! I finally got it tensioned for one type of sewing I do, took DETAILED notes of the tension settings, then went back to try and tension the other way I sew, and it took hours and hours, blah bah blah. Then I need to go back to the first way I sew, and my notes don't work. I can't get it tensioned back. Am I missing something? I am also powering through my thread and using up leather to test samples like crazy. It's wasting so much of my time, and a lot of materials. I've asked Steve, but he hasn't been able to help. I am hoping someone else with a Cobra can offer me some tips?

The first type of sewing I do is one layer of veg tanned about 6-7oz to one layer of chrome tan 3.5 oz. I use a 25 needle, with appropriate thread.

The second type of sewing I do is min 2 layers of chrome tanned, to max about 4-5 layers. I use a 21 or 22 needle, with appropriate thread.

I have got the machine to flawlessly sew both, eventually. But every time I try and tension for the other type of sewing, it takes me hours, days. Or longer. Or I give up (and thank God my old crappy machine still works well enough!)

In these photo examples, you can see how it varies between top tension is too strong, and then too loose. I CANNOT find the balance. (and yes, the top & bottom thread are the same thickeness & brand). It seems I cannot make a small enough adjustment, so it goes between too little and too much tension immediately. Sometimes I can get it to sew normal for 5-6 stitches, but then it always reverts to one way or the other (top is too loose or too tight)

Posted Image

#14 50 years leather

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Posted 18 January 2012 - 10:31 PM

First off 'ART" I don't know much about Cobra machines so don't hit me with one of your classics.

Cath79,

You have a bobbin with adjustment don't you? Are you only adjusting top tension?

This may be part of your problem.

ferg

I am having mega problems getting proper tension my cobra. It's been months of hours, trying and giving up. Going back to hand sewing and my old crappy machine. I am worn out, and confused! I finally got it tensioned for one type of sewing I do, took DETAILED notes of the tension settings, then went back to try and tension the other way I sew, and it took hours and hours, blah bah blah. Then I need to go back to the first way I sew, and my notes don't work. I can't get it tensioned back. Am I missing something? I am also powering through my thread and using up leather to test samples like crazy. It's wasting so much of my time, and a lot of materials. I've asked Steve, but he hasn't been able to help. I am hoping someone else with a Cobra can offer me some tips?

The first type of sewing I do is one layer of veg tanned about 6-7oz to one layer of chrome tan 3.5 oz. I use a 25 needle, with appropriate thread.

The second type of sewing I do is min 2 layers of chrome tanned, to max about 4-5 layers. I use a 21 or 22 needle, with appropriate thread.

I have got the machine to flawlessly sew both, eventually. But every time I try and tension for the other type of sewing, it takes me hours, days. Or longer. Or I give up (and thank God my old crappy machine still works well enough!)

In these photo examples, you can see how it varies between top tension is too strong, and then too loose. I CANNOT find the balance. (and yes, the top & bottom thread are the same thickeness & brand). It seems I cannot make a small enough adjustment, so it goes between too little and too much tension immediately. Sometimes I can get it to sew normal for 5-6 stitches, but then it always reverts to one way or the other (top is too loose or too tight)

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#15 Wizcrafts

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Posted 19 January 2012 - 12:13 AM

I am having mega problems getting proper tension my cobra. It's been months of hours, trying and giving up. Going back to hand sewing and my old crappy machine. I am worn out, and confused! I finally got it tensioned for one type of sewing I do, took DETAILED notes of the tension settings, then went back to try and tension the other way I sew, and it took hours and hours, blah bah blah. Then I need to go back to the first way I sew, and my notes don't work. I can't get it tensioned back. Am I missing something? I am also powering through my thread and using up leather to test samples like crazy. It's wasting so much of my time, and a lot of materials. I've asked Steve, but he hasn't been able to help. I am hoping someone else with a Cobra can offer me some tips?

The first type of sewing I do is one layer of veg tanned about 6-7oz to one layer of chrome tan 3.5 oz. I use a 25 needle, with appropriate thread.

The second type of sewing I do is min 2 layers of chrome tanned, to max about 4-5 layers. I use a 21 or 22 needle, with appropriate thread.

I have got the machine to flawlessly sew both, eventually. But every time I try and tension for the other type of sewing, it takes me hours, days. Or longer. Or I give up (and thank God my old crappy machine still works well enough!)

In these photo examples, you can see how it varies between top tension is too strong, and then too loose. I CANNOT find the balance. (and yes, the top & bottom thread are the same thickness & brand). It seems I cannot make a small enough adjustment, so it goes between too little and too much tension immediately. Sometimes I can get it to sew normal for 5-6 stitches, but then it always reverts to one way or the other (top is too loose or too tight)


First of all, although you haven't said what model your Cobra is, I want to reassure you that the Cobra 441 clones are fully capable of sewing balanced stitches in leather thicknesses from under 6 ounces to over 3/4 inch. I regularly sew with a Cobra Class 4, so I will try to help you with some suggestions.

The 441 clones are not light duty sewing machines. They need a certain amount of top and bottom tension and pressure to operate properly. An overly tight bobbin is as counterproductive as one that has no tension at all. Set a modicum of tension on the bobbin spring for the thread you are using. Not too tight, not too loose. It should pull out smoothly, without any hiccups. Hiccups can be caused by leaving a piece of the tied down starting thread looped around the hole it goes through and the top of that side of the bobbin. Cut off any thread that protrudes from the holes in the end disks of the bobbins.

Thread the bobbins to feed backwards in the case. With the bobbin case open, rotated backwards so the opening is facing back towards the front, hold the wound bobbin so that the thread feeds off the top towards the back of the machine. Place the bobbin in the case and feed the thread through the slot and snap it securely into the tension spring. Make sure the bobbin thread feeds under its spring and out the mouth end, then snap the bobbin case shut. Pull on the thread that protrudes (4 to 6 inches) and make sure the tension has not changed.

Consult the instruction DVD to ensure you are threading the top thread as per Steve's instructions. Before you feed the thread through the needle's eye, pull on it to make sure it is under tension from the top disks. Adjust the spring tension as needed to get a strong amount of resistance, while still being able to pull the thread a bit. Lift the presser foot release lever with the foot pedal and see if the thread pulls easily. Let go of the foot lifter. Now lift the hand presser lifter on the back and see if the top tension has been released at all. I find that the hand lifter only releases a little top tension, whereas the foot lifter lets it go almost completely.

The hand or foot lifters, when lifted, should force the top disks apart (with a little lever that moves from the bottom of the disks) to release thread tension. Then, when you release the lifter, the lever that splits the disks must drop down to allow the disks to close and pressure to be applied, as set by the finger adjuster nut. If this lever is sticking in the disks, the tension may not be properly applied to the thread.

If the check spring has too much tension, it can cause additional drag on the top thread. The spring has two possible adjustments. Once is the movable stopper plate under it, which sets how long the top thread is kept taut during the down stroke.This is set by the single flat head screw that sits inside the slot in the stopper plate. This is a trial and error adjustment. You don't want it to stop short, nor all the way down, in most cases. set it somewhere in between. If the spring has a LOT of tension, reduce it by loosening the nut on the back of the face plate where the bottom disk shaft is mounted. With the nut loose, insert a small flat bade screw driver into the split shaft and turn it whichever way loosens the spring action. Loosen the spring a little then tighten down the locking nut.

Make sure you thread through the needle from left to right, with the cutout scarf facing the dead-right side.

If you are using a #25 needle, it works best with #V207 or T210 thread, top and bottom. It will feed #277 on top, but 207 on the bottom is easier to pull up into the leather. If the leather is soft temper, you may be able to get away with a #25 needle and #277 thread, top and bottom.

For #138 thread, I use #23 leather point needles. Yes, a 21 or 22 works, but the #23 seems to sew more reliably. Use system 794 Schmetz needles if possible.

Set the top pressure spring adjuster so it sticks out the top between 1 and 1.5 inches.

Before you start sewing, hold the top and bottom threads back hard. Sew in reverse a couple stitches, then throw the lever to forward and cross over the starting threads. Let go of the threads and sew slowly for a few inches. Lift the foot lifter and remove the leather. Check the position of the knots. If you see the top thread knots on the bottom, increase the top tension adjuster. If the knots are on top, reduce the top tension.

If the stitches look decent, sew a longer run of stitches, using your edge guide. As your machine is sewing, look up at the top thread and see if it is winding around anything and causing knots to form. Also, see if it is trying to twist out of the top tension disks. I have actually seen a knot forming as the top thread twists after going through the post on top of the machine. When that happens, try changing how you feed it through that post. Twisted thread causes tension problems. It can even twist right out of the top tension disks!

Some thread is just plain shitty. If you have really springy thread, remove it and try another brand, or another spool. Thread can vary from run to run.

If the thread is feeding properly, without kinking or knotting, and without popping out of the center of the top tension or bottom tensions disks, and the bobbin thread is feeding evenly, with a bit of resistance, using the proper needle size for the top and bottom thread, your stitches should all fall into the same vertical position in the leather. Failure to do so indicates that there is either a problem with the thread or the machine needs adjusted. Sometimes a screw may shake loose and affect the timing or repeatability of good stitching. Please rule out everything else before you assume that the machine needs to be adjusted beyond the tension settings I mentioned.

I will watch for your replies tomorrow morning, or night. I'll be out all afternoon.

If you get a chance, photograph how you are threading the top thread, from the spools, all the way to the needle.
Posted IMHO, by Wiz





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