Do you like this presser foot?

[Gymnast]

5 hours ago, dikman said:

Gymnast, there's no doubt about it, you are a nerd extraordinaire!

I suppose I earned this reputation  And based on the number of people seeing this video, I am not the only one.

[kgg]

I do find the thread, haha, subject interesting as it may not be so important on industrial machines that have greater punching power to overcome some tension related issues. I think the principals can be well applied to improve the domestic machines sewing abilities. Now if someone could figure out how to put a real walking foot (not the domestic walking foot attachment) on an old iron that would give real life back to some of the old stuff. We all have our own pet peeves and quirks, one of mine is improving / eliminating thread backlash mostly by redesigning the cheap thread stand and how the thread spools are held in place ( New accessories for my Juki 1541S and sewing Table, #3 ).

[Bert51]

Thank you Gymnast, I think we are learning all our lives and if I can find anything that may help me with my endeavors, then I am interested. I think you have extended my learning curve and make me think how I can improve my sewing.

Again thank you.

Just added this video to your folder.

Bert.

[Gymnast]

I just noticed this video from 2016 with a presser food designed with this thread notch. So I am lucky to not be the first one with this idea. This food seems to be on a high shank straight stitch drop foot machine: 

I just noticed, that this is a needle feed machines, so therefor the presser foot design is different. But the presser foot do have a remarkable long thread slid to the back near the hinge of the foot.

Edited April 23, 2020 by Gymnast

[Gymnast]

I made a small extra study of this presser foot with a notch to the back and the big roller foot, that got some of the same way of enhancing feed of a drop feed machine. The main reasons to use these presser foots is to significantly improve feed traction on drop feed machines.

If you operate a drop feed machine with the normal foot, I like you to pay attention to how the stitch is formed. The upper thread is pulled up by the take-up lever, thread tension is applied and the lock of the stitch pulled up and ideally placed in center of the fabric stitched. It is however not only the take-up lever that pulls the thread, because the feed moves the fabric forward, and it is pulling the threads too. For most drop feed machines set to 4 mm stich length, you will get about 1.5 mm pull of thread with about twice the thread tension by the feed.

I think I need to explain a bit more in detail what is going on for these normal drop feed machines. This is a simple test set up to measure the thread tension at the foot:

With one setting of the tensioner, the take up lever can pull up to a thread tension of 3.8 N in thread measured by the spring dynamometer when the thread pass at the tensioner. If you pull in the dynamometer you will get a tension of 7.0 N when the thread pass at the tensioner. The higher tension is due to the thread friction to presser foot and a few fixed thread guides. This is why the feed can pull harder in the thread than the take-up lever motion.

When you sew thin fabrics of about 1 mm, then it becomes very hard to set the correct thread tension to get a balanced stitch. It easily may be placed sometimes at lower surface and sometimes at top surface. But this last hard short pull by the feed helps a lot to make a balanced stitch in this situation. If you like to see more about the timing of the feed in relation to the take-up lever and how this is, you can look at this video - the link will start the video when the thread is around the shuttle:
https://youtu.be/WqFjQyrKnO8?t=455

When you use the presser foot with the notch to the back or the similar large wheel presser foot, you interfere with the stitch forming and help from the feed, and therefore it makes it almost impossible to make a balanced stitch in 1 mm thin fabrics. The same will happen if you for some other reason advance the timing of the feed. Therefore I cannot recommend to use this kind of foot on such thin fabrics. I have tried to experiment with fabric thickness. If I had 2 mm or more thick fabric, you can get good control of the stitch balance again with the foot with the notch or large roller foot. Thicker fabrics makes it easier to make a balanced stitch, and then this help from feed is less needed.

I guess, that walking foot machines have no means of increasing the thread tension in the same say, so they will have similar problems with thin fabrics to make a balanced stitch.