Cobra class 4: 346 bonded polyester thread? Help!

[DieselTech]

Guys & gals I have a Cobra class 4 & it was set up for 277 thread & sewed fine. 

I need to sew some rear flank billets for a saddle. The billets are 9mm thick that I need to sew. Which they will be 2 layers. They will be constructed using 5mm veg tan saddle skirting & 4mm Latigo, both Hermann Oak. 

Ok. So here we go: I swapped the thread over to lubricated 346 bonded polyester thread, both on top & in the bobbin. #25 Schmetz D point needle.

So when I 1st started sewing, it kept picking up the leather when the needle was coming up. So I increased the presser foot tension, by 20 turns in. 

So now it no longer picks the leather up when the needle is on the up stroke, but at 1st it kept breaking my top thread. 

So I re-threaded it 3 times before it stop breaking my top thread. 

So now I got it sew thru 2 layers of 6mm saddle skirting, but it made lot of squeaking as the needle came back up thru the leather. 

So my question is: Why did it keep snapping my top thread at the beginning of sewing? Was it because my thread is 8-10years old? (Thread was in zip lock bags stored in the dark) if that matters on its age?

Or because of the #25 needle is too small & I should go to a #26 needle? 

Should I be running a lube pot? Only running my machine at 200 rpm. 

Thanks. Any help or pointers will be greatly appreciated. 

[DieselTech]

Also I forgot to mention, I am using @Patrick1 #25 throat plate & feed dog. 

Also would switching to a different needle point change anything. Like go to a #25 S point leather needle? 

Thanks. 

[CdK]

Did you adjust thread tension after going to the thicker thread and needle? I had similar trouble and solved it by reducing the top and bottom tensioning.

[DieselTech]

19 minutes ago, CdK said:

Did you adjust thread tension after going to the thicker thread and needle? I had similar trouble and solved it by reducing the top and bottom tensioning.

No I have not touched the thread tension since switching to 346 poly thread.  But I will mention that when I was using 277 thread I had to tighten/increase bobbin tension by 1 full turn on the bobbin thread tension to get it to even the stitches out. 

Should I decrease my bobbin tension by 1 full turn back. This will put the bobbin tension back to how the machine was shipped to me. 

Thanks.  

[DieselTech]

Ok. I cut 2 pieces of the actual leather I will be sewing. Looks Ok to me. I think my feed dog height might be a touch high. Or I need to back the presser foot tension off a bit. I'm not sure, I'll have to do some more practice/testing. 

[Constabulary]

Playing with top and bottom thread tension and adjusting foot pressure is part of the sewing game when sewing different thicknesses or using different thread / needle sizes. You have to practice this.

You just need as much foot pressure that the materials is not lifted by the rising needle.

To me the needle holes look fairly large but I have not used D point needles. My preferred needle is the S point needle for having a straight seam look.

[DieselTech]

10 minutes ago, Constabulary said:

Playing with top and bottom thread tension and adjusting foot pressure is part of the sewing game when sewing different thicknesses or using different thread / needle sizes. You have to practice this.

You just need as much foot pressure that the materials is not lifted by the rising needle.

To me the needle holes look fairly large but I have not used D point needles. My preferred needle is the S point needle for having a straight seam look.

Thanks. Yeah I am going to switch to a S point needle in the morning. Then start playing with my presser foot pressure too. I think it needs backed off a bit now or I need to lower my feed dog height a touch. 

I guess it all part of the game, plus I haven't had my Cobra class 4 out & sewing in probably 4 months or longer. 

Thanks. 

[DieselTech]

Ok I switched to a #24 S point needle & backed off my presser foot presser by 2 turns. 

The 2nd stitch line in from the edge of the leather is the # 24 S point needle. 

I think I could get away with a # 24 S point needle with the lubricated polyester 346 thread. 

I'll continue to decrease my presser foot pressure, until the presser feet tracks go away or at least try. 

[Constabulary]

Foot pressure if often overlooked and folks keep it high when the last project required high foot pressure. Guess how I know (different machine though). I sew thick leather only now and then and I always do some tests before I start the project. Speaking of thread tension - a leather worker I know even has different hooks for different size thread and has marked the hooks with the specific thread size but he is using linen thread from one manufacturer only - no poly and no nylon.

To me the needle holes still look fairly large - or not?

[DieselTech]

5 minutes ago, Constabulary said:

Foot pressure if often overlooked and folks keep it high when the last project required high foot pressure. Guess how I know (different machine though). I sew thick leather only now and then and I always do some tests before I start the project. Speaking of thread tension - a leather worker I know even has different hooks for different size thread and has marked the hooks with the specific thread size but he is using linen thread from one manufacturer only - no poly and no nylon.

To me the needle holes still look fairly large - or not?

Let me ask this? Cause I don't know. Can your thread tension be soo tight it causes your needle holes to elongate from high thread tension? Causing the stitch/needle holes to appear/be enlarged?

Lmao last time I used this machine I sewed 2 layers of 5oz Conceria Walpier Buttero with 277 thread. 

The time before that I sewed 2 layers of 2oz Conceria Walpier Dollaro with 138 thread & a #23 throat plate & feed dog.