Tips on Sewing Biothane?

[TomE]

On 9/16/2025 at 10:59 AM, Wizcrafts said:

Coincidentally, I had a customer come to my shop yesterday with a dozen webbing straps that I had to sew together in pairs, at the loose ends, with a 3" overlap. I chose #138 yellow bonded polyester thread and used a #23 round point needle. I had to retime/advance the hook to avoid skipped stitches in reverse, and adjust the check spring throw, in addition to increasing the bobbin and decreasing the top tension. All of the tension changes will have to be undone when I have to sew a holster or sheath.

Thanks for this information.  I will look at the check spring settings on my Class 4 today.  This could be an issue because I installed the Hennigan holster plate with feed dog to provide more clearance when sewing next to a center bar buckle. 

I am doing a reasonable job sewing 2-3 layers of Biothane Beta super heavy (3.5-4mm) using black #207 thread top and bottom, and a size 26 S-point needle.  I've had problems with loose bottom thread (loops) when using round point needles (sizes 25, 26, 27), usually when sewing 3 layers and sewing next to hardware.  I did increase the foot tension considerably.  With the holster plate installed there is barely enough clearance to sew 3 layers of extra heavy biothane, especially at the ends that wrap around hardware.   The turn around the hardware is very springy and I'm using my fingers to compress the turn when sewing towards it.

I have a silicon thread lube pot installed but I don't detect the lube when running the thread through my fingers.  Maybe it's enough?

I have also noticed a problem with the black thread twisting.  I saw your comment in the link below about countering twist by wrapping around a thread guide post.  My Class 4 didn't come with any guide posts so I guess I'll call LMC to request one.

  https://leatherworker.net/forum/topic/98583-help-needed/#findComment-668610

 

Biothane has been a curse and a blessing.  I am learning more about my machine and improving my skills.  As always, I appreciate the advice from you and others on this forum.