Help Needed

[RickV]

 

Here is the bottom side.

Here is where i am stumped.  I removed the tension spring from the bobbin.  Thinking that it would surely pull through the top and leave me with a straight line for my top thread as there was no tension what so ever on the bobbin.  The thread still pulled through the bottom. images to follow.

[RickV]

  Top side

Bottom side with bobbin tension spring removed.

[DrmCa]

The condition of your bottom thread surprises me. Why is it so unspun? Try a different thread, just for giggles.

Edited December 21, 2021 by DrmCa

[RickV]

1 hour ago, DrmCa said:

The condition of your bottom thread surprises me. Why is it so unspun? Try a different thread, just for giggles.

It looks like that due to the fact that its pulling through the bottom so hard but, I am stumped cause ive never seen a machine pull thread through the bottom of the leather without a tension spring on it. I removed the tension spring from the bobbin case to see what would happen and the issue im having still remains. It makes no sense to me that it would pull through like that with the tension spring removed.

[kgg]

1 hour ago, RickV said:

Our current needle size is 135x17 and the thread weight is 135

The number 135 x 17 is the system of needle you didn't mention the needle size. For leather you should be using a 135 x 16 with a #22 needle for thin leather and #23 needle or even #24 needle for thicker leather. The 135 x 17 needle system you are using is mostly for fabric.

The spec I seen on your machine says the max needle size to be a #23. To me this would indicate it being rated for a #23 needle the machine is probably rated for V92 thread top and in the bobbin in thick and V138 top and in the bobbin in thinner or fabric. This would be similar to the rating of a Juki DU-1181n (flatbed) which is factory rated for V92 thread top and in the bobbin but can accommodate a #23 needle for V138 thread. In some materials depending mostly on thickness I can use V138 thread top and in the bobbin and others I have to go down to V92 thread top and in the bobbin.

From the photo showing how the thread is unwrapping / seperating I think the hole the needle is making isn't large enough and rolling the thread slightly so it is unraveling. Looks to me like a polyester type thread. As a test go down to V92 bonded nylon or polyester with a leather needle (135x16 #22 or #23) as see what happens.

kgg

[Wizcrafts]

5 hours ago, RickV said:

Our current needle size is 135x17 and the thread weight is 135

As @kgg mentioned, 135x17 is a needle "system," not a needle size. Each needle system will have a range of available sizes that are shown in either the US Singer numbers or the Metric system. The proper needle size for Tex 135 thread, top and bottom, is Singer #23/Metric 160. As already mentioned, system 135x16 are leather points. So, you need to buy System 135x16 needles in "size" 23/160 to properly sew with T135 thread. By the way, T135 is almost the same as B or V 138. Here is a convenient needle and thread reference chart that shows the diameter of different sizes of thread and the proper needles to sew those sizes. Where two needle sizes are shown, the larger is used in denser veg-tan leather. The smaller would be used in softer upholstery and chrome tan leather.

[RickV]

21 hours ago, Wizcrafts said:

I have a clone of that machine: a Techsew 2700. If your bobbin thread keeps popping out of the tension spring, reverse the direction of the tbobbin. I usually insert bobbins so they feed against the direction of the slot and spring. This ensures  good, controllable tension and keeps the thread from jumping out of its channel. Make sure that both little screws are holding the spring in place. The one closest to the exit position controls the tension. The other one keeps it in place on the case. If you are unable to get adjustable tension in the bobbin case, replace it!

Assuming you can gain control of the bobbin tension, check the entire top thread path for kinks or sharp turns, or excessive twisting from overly coily thread. If your thread is too twisty, replace the spool and try balancing the tensions again. Or, counteract the twist using the holes in the top guide post. I do that anyway, feeding through the top hole, bringing the thread around the front, then through the bottom hole. This gives a counter twist to offset any twist in the thread cone.

Make sure you are threading correctly according to the manual. Adjust the check spring tension so it only has enough force to bring the spring down against the back stop bracket, wherever it is set to stop the spring. Then adjust the position of the slot to give the best lay of the thread without making a popping sound as it goes around the bobbin case and shuttle.

Finally, if you still have trouble with the tension, remove the top tension spring and disks and inspect them for burrs. Ditto for all the guides and even the take-up lever. Do not wrap thread around the pin on the right side of the top disks. It is not there for that purpose.

Interesting. What is the purpose of the pin? i was under the assumption that the thread has to wrap around the pin to sew properly.

[Uwe]

I don't think the bottom tension is the culprit, the bottom thread is clearly loose in the picture

I suspect the problem has to do with a snag of the top thread as it's wrapped around the hook. The bobbin case opener, the opener finger, and the cast-off gib on the hook, are all candidates for top thread snagging opportunities.

If the top thread snags at any point during the stitch cycle, more top thread may be pulled from the spool through the top tension unit, which make it impossible for the take-up lever to pull the knot tight, regardless of tension settings. No matter of tension adjustments will fix that kind of snag.

The ONLY time top thread is allowed to be pulled through the tension unit is when the take-up lever is at the very top of its movement.

A few slow, hand-turned stitches while closely observing how the thread wraps around the hook is usually key to debugging this type of problem.

 

The purpose of that pin is to keep the tension disks from spinning, which would cause the thread to slip out from between the tension disks.

Edited December 22, 2021 by Uwe

[kgg]

1 hour ago, RickV said:

Interesting. What is the purpose of the pin? i was under the assumption that the thread has to wrap around the pin to sew properly.

To help with your thread problems a couple of pictures detailing how you have the top thread routed from the thread spool to the needle along with the size of needle could probably help solve your problem.

kgg

[Wizcrafts]

2 hours ago, RickV said:

Interesting. What is the purpose of the pin? i was under the assumption that the thread has to wrap around the pin to sew properly.

The pin it there to hold the tension disks in place so they don't rotate with the moving thread. The pin on these types of sewing machines is not meant to have thread wrap around it. First, this puts kinks in the thread, causing unpredictable tension changes. Second, it eventually wears a groove in the pin that will rat the thread.