presser foot lifting during stitch

[jollyroger]

I am relatively new to sewing leather and recently purchased a Sailrite Leatherworker sewing machine. I've managed to sew a few belts and straps successfully until yesterday. The machine started fraying the thread at the needle to where I would have to stop the stitch and rethread. Then the presser foot started lifting during the stitch and it would skip multiple stitches. 

I have made sure there are no strikes or burrs in the gib hook. Timing looks appropriate and needle bar is set correctly. I haven't adjusted anything else. I made a short video of what the machine is doing:

I would appreciate any thoughts on what I've got going on here... Thanks in advance.

[Northmount]

1 hour ago, jollyroger said:

Then the presser foot started lifting during the stitch and it would skip multiple stitches. 

You should have noticed that the leather is lifting the presser foot.  This happens with dense hard (and thick) leather.  The needle sticks in the leather and pulls the foot up with it.  Of course that destroys the loop so the hook can't grab it.

Increase the spring pressure on the presser feet.  Lubricated thread can help too.

[jollyroger]

I usually wait to sew the belt until after I've oiled it. Do you think that would help?

I tried sewing another piece of 8-9 oz leather that I did not color and did not have the same problem. It seems to be only the colored leather. I haven't had problems sewing color leather before that's 8-9 oz but it's always been oiled first. 

I tried increasing the spring pressure on the presser foot (a little, then a lot) and there was no change. Seems like the thread gets caught somewhere and causes it to lift the leather up against the presser foot.

Edited Saturday at 08:04 PM by jollyroger

[Northmount]

45 minutes ago, jollyroger said:

I usually wait to sew the belt until after I've oiled it. Do you think that would help?

I tried sewing another piece of 8-9 oz leather that I did not color and did not have the same problem. It seems to be only the colored leather. I haven't had problems sewing color leather before that's 8-9 oz but it's always been oiled first. 

I tried increasing the spring pressure on the presser foot (a little, then a lot) and there was no change. Seems like the thread gets caught somewhere and causes it to lift the leather up against the presser foot.

I'd be careful of how much NFO I add to the leather.  Too much and you have a soppy mess.  It should help.  The thread would likely break before it would lift the presser foot.  Lubricated thread lubricates the needle so helps.  Some members have sprayed their thread (on the cone) with silicon spray and let it soak in well.

You might even hear a squeak as the needle pulls out of the leather.

[jollyroger]

I don't hear a squeak, just that loud kind of pop you can hear in the video. Ok, I'll try the silicon.

[jollyroger]

Got some spray silicone from the hardware store. I sprayed the thread and made sure it was all wiped down, then redid the bobbin with the same lubed thread. I tried three different times and each time, skipped stitches and, foot presser wheel starts lifting and the thread frays or tears. This leather isn't any different than the regular veg-tanned leather that seems to work without any problems. 

You think this has to do with the thickness or density of the leather? I can just color after sewing. Am I left with sewing this particular belt by hand?

Would it help to sew it while it was damp?

Edited Sunday at 01:04 AM by jollyroger

[Northmount]

2 hours ago, jollyroger said:

You think this has to do with the thickness or density of the leather? I can just color after sewing. Am I left with sewing this particular belt by hand?

Would it help to sew it while it was damp?

It definitely has to do with thickness, density and hardness of the leather.  It is gripping the needle and rising with the needle.

Moistening the leather will make it softer, easier to pierce and retract.  It will also leave more machine marks.

Are you using a leather point needle?  It looks like you are, and should be better than a conical point.

[jollyroger]

v92 bonded thread and 135x16 DIA needle. I will wet it and see how it goes. Thanks for your help.

[kgg]

2 hours ago, jollyroger said:

v92 bonded thread and 135x16 DIA needle. I will wet it and see how it goes. Thanks for your help.

The leather and needle are lifting the presser foot like @Northmount has noted but also catching the thread as indicated by the loop being created at the needle.

The 135x16 is the correct needle system for leather but what size of needle are you using? 

Here is a good chart for needle size verses thread size but in thick or tough material you should move up a needle size. If you are using a #20 needle go up to a #22 needle. The machines max needle size is a #22 and the max thread size is V92. I have owned a couple of Sailrite LSZ and clones and real life will show you with tough / dry / dyed leather you are at roughly the max sewing thickness that machine can handle. Also what I did find with those machines: i) is they can be really particular with the needle being installed as in that it almost has to be perfectly installed and any deviation especially in leather you can run into problems. ii) stitch length will vary as the sewing thickness increases.

kgg

 

[Constabulary]

The the friction between leather and the rising needle lifts the presser foot. I´d increase the foot pressure first. If it does not help look for a heavier spring for the foot bar.

[jollyroger]

I increased the spring pressure but too much and it will mark the leather. Either way, it seems the vinegarroon process changes the density/hardness of the leather. But it won't affect the thread so I'll just stitch before tooling and coloring. 

I finished up the stitch on the belt by hand. I started a new belt this morning with the same exact leather prior to coloring and had no problems, so thank you everyone for pointing me in the right direction.