Intermittent tension issue

[kgg]

2 hours ago, hanns said:

Are you referring to this?

Yes. That is the correct location for the vertical guide pin. Your main thread has to be threaded through this before going to the horizontal guide that is located just above the bobbin winder. I would recommend you have your top thread come from the top arm of the spool stand for your top thread directly vertical pin.
When threading this vertical pin with your top thread it will cross over the large round dial for adjusting the amount of lift for the pressor foot and walking foot. So that the top thread doesn't touch the top of the dial you thread this pin by going into the bottom hole first and out of the top hole. The hole in the top arm of the spool holder for guiding your top thread ideally will be as close to being horizontally level and create a straight line from the horizontal guide to the top arm guide hole.This may pose a problem with the type of spool holder you are using.

So you can wind a bobbin while happily sewing along you could replace the 2 hole pin with a 4 hole vertical pin or do something similar to my solution or just have your bobbin thread come directly from the top arm guide hole directly into the bobbin thread guide.

 

16 minutes ago, RockyAussie said:

Why do they make the tension disks so smooth and curved and decide that after all that to put in a flat holding piece????

My take on this is that it holds the top thread for a split second acting as a damper so the thread doesn't go slack or to tight in the cycling of the top thread arm and reduce unwanted thread movement at the needle. Some other machines don't use this at all while others particularly in the 341 class use a felt pad inserted in the guide just below the take up level to achieve the dampening effect. The spring loaded flat piece system is also used with some 2 needle systems to help keep the two threads separated during the sewing cycle with one thread being on each side of the screw. I have used my 1541S both with and without the flat wiper. I found not much if any benefit when using V69 or V92 but a difference with black V138.

Just my two cents worth

kgg

[Gymnast]

13 hours ago, hanns said:

I wasn't 100% convinced the issue was resolved, so I spent more time today testing and sure enough there it is again. I was thinking about your test here as well as the issues people seem to have with these smaller spools, so decided to test that part in isolation and video it. Thread seems to be getting snagged before it even gets to the tensioners.

 

If you look at the linked video about thread twisting, you will find, that it is important how you make the pass of the thread through the steel plate with holes in it. You go clockwise in forward direction. I would chose to go anticlockwise to reverse the twisting from this steel plate.

[hanns]

9 hours ago, RockyAussie said:

check to see what results you get when you don't have the thread going under that spring thing down below the thread take up lever.

I forgot to mention: I did try this. I just removed the screw and the little spring arm assembly to get them out of the way so the thread could go through the guide freely. It didn't make any difference in this case, so I put it back on.

Edited May 23, 2021 by hanns

[Wizcrafts]

You need to wrap the thread counter-clockwise around something to counteract the twist of the wound spool. It could be a post that has holes on the top and bottom, or the guide before the pre-tensioner.

[LindanHotAir]

In one of the photos it looked like the thread was going through both tensioners. Normally 2 tensioners on a single needle machine allow the operator to set them up for 2 different threads. Thread through the pretensioner which is normally used to control the cutting length, and normally starts out with the knob flush with the end of the screw. Then use one tension assembly, then thread the check spring assembly. The check spring should operate to prevent the thread from going slack between the tension and the take up lever.