Pfaff 335 tension issue

[Woehlk]

Help me!, im lost!. spendt 5 hours yesterday at this, and have not gotten any wiser!. Something is totally wrong with my tension. I can make it perfect, and then, it skips a few. I use Schmetz 134 LR size 21, and Serafil 20 Tex 135

 

[Woehlk]

No one have an idea how to fix this? 

[shoepatcher]

thread size and needle you are using?

More pics of the the tension area please.   Also the model plate in front.  Pics lease.

glenn

[Woehlk]

Hey Shoepatcher!, thanks for your answer!, here is the front and backsides. When the knot gets at the bottom, and even though I just change the upper tension the slightests, the knots get on top. Even trying one several meters of leather, I cannot find the sweet spot. 

The leather is 3.5mm thickness. 
Needle is SCMETZ NM; 130 SIZE: 21 134 LR
Thread is is Serafil 20 Tex 125

Bobbin tension: I do the drop test. where I drop the bobbin like a yoyo, and the thread gives a little. 

Edited March 5 by Woehlk

[kgg]

56 minutes ago, Woehlk said:

The leather is 3.5mm thickness. 
Needle is SCMETZ NM; 130 SIZE: 21 134 LR
Thread is is Serafil 20 Tex 125

The needle size is incorrect for Tex 125 (V138). Reference needle size to thread size ( https://www.tolindsewmach.com/thread-chart.html ). That size of thread you should use a 140 (#22) or 160 (#23) and in thick or tough leather 180 (#24). 

That said the PFAFF 335 is regarded as a binding machine with the older casing machines rated for a 120 (#19) for a Tex 90 (V92) thread. Reference manual ( http://docs.uwe.net/Pfaff-335-Instruction-Book-Old-Casting.pdf ). The newer body machines are rated to a 100 needle. When you go above the rated max's of the machine you could or probably will have problems with needle to hook clearances, etc. which then can result in other stitching / tension problems.

kgg

[Woehlk]

Thank you so much Kgg!, I had researched the needle to thread before, Just talked to some fellow danish leatherworkers, that said it was okay. they said the thread just needed to be inside the channel of the needle. 
 

But you have real references, so that is something I can actually use!. 

Would you recommend me buying new thread? or new needles. or both. 

And if yes, what sizes 

[kgg]

8 minutes ago, Woehlk said:

Would you recommend me buying new thread? or new needles. or both. 

If you want to use V138 buy a machine like / similar to the class 341/1341 like a Juki LS-1341 or an older Juki LS-341 or their clones. Otherwise reduce the thread size to a max of V92 with the correct needles in your projects. Personally I think this is the wrong class / type of machine for your needs in 3.5 mm leather. If most of your projects are leather be done with it and get a new / used Class 341/1341 machine.

kgg

 

[shoepatcher]

You can sew #138 on a Pfaff 335 but you must enlarge the hole in the feed dog and inner foot to accommodate the #138 thread.  I also just touch the the corners of the  space bar on the  the machine.  That is where the gap on the bobbin case is that the thread passes by the each stitch.  335 Pfaff do not have a bobbin case opener since they are a horizontal hook machine.

glenn

[dikman]

I have an old casting 335 and after much tinkering and adjusting I got it to sew #138 - but it wasn't happy about it. It was much better with #69.

[shoepatcher]

22 minutes ago, shoepatcher said:

You can sew #138 on a Pfaff 335 but you must enlarge the hole in the feed dog and inner foot to accommodate the #138 thread.  I also just touch the the corners of the  space bar on the  the machine.  That is where the gap on the bobbin case is that the thread passes by the each stitch.  335 Pfaff do not have a bobbin case opener since they are a horizontal hook machine.

glenn