Lower thread

[Michiel]

The small spring in the middle of this picture was not working properly

and  that caused the under thread being pulled at the wrong moment

and that was why the under thread went out of his designated  place…(on my machine)

 

It happened mostly when sewing backwards (and not always)

[Michiel]

Picture is from an old topic on lwn

not my machine, not my picture (and now i notice it is not threaded right,so do not thread your machine this way! But check if the spring is working well)

Edited 16 hours ago by Michiel

[RockyAussie]

On 10/5/2025 at 7:12 AM, Romana said:

I can't even record a video to make it look good. What I mean is that the machine sews well for a while and then seems to jerk in places. I attributed it to the lower bobbin thread coming out in the middle.

I think you may find that the main problem you are having is caused by the top thread cones not being the right type for running vertically as you have them. Most leather workers would use cones with a splay at the bottom which stops the thread from getting hooked up as it pulls off of the cone at the bottom. Also most will use either a bonded nylon or bonded Polyester thread which will behave a lot better going the through the tension guides.