Why is the feed dog timing like this?

[Gymnast]

This is a general question, that relates to a more "normal" sewing machines with ordinary drop feet (not walking foot).

Most people with some knowledge of sewing machines know about, that the timing of the hook in relation to the needle is important. But the timing of the feed dog are not an issue in the domestic sewing maschine service manuals, that I have seen. I have checked the five sewing machines i got, and they all have a similar timing of the feed dog, and it seems to me that the timing is about 30 degrees late. I think that the designers of sewing machines must have a reason for that, I just like to know why. For domestic sewing machines, there may be some jobs of soft fabrics of high thickness, that a user may like to use the machine for. But this seems not made possible by the chosen timing.

I made this video about the issue. I hope someone here may have an answer to the question - why the normal feed dog timing is like that?

The cover picture of the video shows the measured position of the feed dog of my Singer 201k.

[CowboyBob]

On the 66 machine in the video the feed dog is adjusted too high.I would lower the height,you should also be able to adjust the feed cam alittle to keep it from feeding as the needle goes in the leather.The 201 machine with the style of hook in it is most suited to keep using lightweight thread & sew what it was designed for.The best models to modify for sewing leather are the Singer 15 class,they have an adjustable feed cam & oscillating hooks like the Singer 31-15 & will take the # 69 nylon better than the 66&201 will.

[Gymnast]

1 hour ago, CowboyBob said:

you should also be able to adjust the feed cam alittle to keep it from feeding as the needle goes in the leather

Thanks for your answer.

I do not think, that it is possible in an easy way to adjust the feed dog timing of the Singer 66 "just a Little". If you see how I adjusted the 201 in the video, you got the same kind of grove in the shaft for the pinol lock screw on the Singer 66 (I suppose the Singer 15 got the same). That means, that if you just do a little advance of timing, the pinol will move the eccendric part back into the factory timing again. To avoid that I think you need to advance the timing at least about 25 degrees. But I guess this will be in order too, unless I should look out for something I do not know about yet.

[Wizcrafts]

This is fascinating from a theoretical viewpoint, but begs the question: why are you trying to force domestic sewing machines meant to thin cloth to sew 6mm of leather? It makes no sense unless you simply cannot find an affordable industrial sewing machine that allows full calibration of the feed components.

This topic reminds me about some past discussions of portable walking foot machines that were built to sew sail cloth and boat upholstery. Owners were trying all kinds of hacks to get them to sew over 1/4 inch (6mm) of leather with #138 or larger thread and had very mixed (mostly bad) results. Those machines were not built with that work in mind. The same goes for the Singer 66 and 201. Singer's engineers designed them for household repairs to cloth garments, some of which were stretchy, and  they are good at doing that. They made better, stronger and more adjustable commercial machines for heavy duty sewing into thick materials and leather.

[nylonRigging]

You tuned it to your specific needs . You now advanced feed dogs, and you slow-speed stroke the needle plunge thew thicker materials  . 
 now with your new tune-up . For my curiosity, what I would like to see .. Try sewing with lighter thread and using lightweight fabric with 'speed ' on a straight run stitching, like the machine was built for .
.

[Wizcrafts]

The feed motion shaft could have another channel cut for securing the offset feed timing.

I think that the current feed dog motion is best suited to stretchy cloth, not hard materials.

[Gymnast]

11 hours ago, nylonRigging said:

For my curiosity, what I would like to see .. Try sewing with lighter thread and using lightweight fabric with 'speed ' on a straight run stitching, like the machine was built for .

I will try that.

11 hours ago, Wizcrafts said:

The feed motion shaft could have another channel cut for securing the offset feed timing.

Yes, it is a possibility, but I consider it to be a rather costly operation in time and effort.

11 hours ago, Wizcrafts said:

I think that the current feed dog motion is best suited to stretchy cloth, not hard materials.

I am not quite sure of the history of garments here and how early stretchy garments were produced in large quantities. I know that in the past 40 years much more cloth are made of stretchy fabrics. The Singer 66 I got came from factory in 1930 and the design goes further back. It do have this late timing of feed dogs anyway. I think, that a normal streight stitch machine is not that good for stretchy fabrics. Zig zag or double needle is better. And some computer machines make special patterns. I guess that sergers are common to be used for stretchy fabrics today.

I got this link with the information, that a fashion designer started to use jersey in 1924: https://www.fulgar.com/eng/insights/jersey-fabrics

Edited December 30, 2019 by Gymnast

[Constabulary]

Really? Once again domestic sewing machine sciences?

[CowboyBob]

22 hours ago, Gymnast said:

Thanks for your answer.

I do not think, that it is possible in an easy way to adjust the feed dog timing of the Singer 66 "just a Little". If you see how I adjusted the 201 in the video, you got the same kind of grove in the shaft for the pinol lock screw on the Singer 66 (I suppose the Singer 15 got the same). That means, that if you just do a little advance of timing, the pinol will move the eccendric part back into the factory timing again. To avoid that I think you need to advance the timing at least about 25 degrees. But I guess this will be in order too, unless I should look out for something I do not know about yet.

Just go past the groove,I've done it before,as long as the screw is tight it doesn't need to be in the groove.

[Gymnast]

36 minutes ago, CowboyBob said:

Just go past the groove,I've done it before,as long as the screw is tight it doesn't need to be in the groove.

Thanks Bob. Thats exsactly what I did with the Singer 201. I checked the Singer 237, and it do not have this possibility of adjustment, because the excentrics for the feed dog stroke and the hook movement is a part of the steel shaft it self. So not all machines can be adjusted for that.

13 hours ago, nylonRigging said:

For my curiosity, what I would like to see .. Try sewing with lighter thread and using lightweight fabric with 'speed ' on a straight run stitching, like the machine was built for .

I tried to sew two kinds of garment with my Singer 201 with and without the forwarded timing of the feed dogs. I was not able to see a change in stitch quality. But I saw a significant change in the required tension from the top tensioner to get a ballanced stitch:

When you look at the timing diagram above in thread start, you still do have some movement from the feed dogs after the take up levers is at max. Therefore the movement of the feed dogs are involved in the final stitch forming and tension on the top thread in the fabric. With the changed timing, the feed dogs have finished the movement when the take up lever is at max. Therefore this may require more tension from the tensioner.

I guess that the sewing machine designers wanted, that the feed dog movent got involved here in the stitch forming, but I am still not sure why.

Edited December 30, 2019 by Gymnast

[Wizcrafts]

Maybe I will have to create a new forum section to discuss domestic sewing machines. Let me study on that. That way folks wanting to delve into the mechanics and design parameters of household machines may get more useful interactions than in this leather sewing machine section. This forum is really targeted at industrial leather sewing machines, not household machines that might could sew leather, nor industrial machines meant for high speed sewing of broad cloth and man made materials.

If I get the go-ahead and do create a non-leather sewing machine forum I will link to it as a sticky post.

[Gymnast]

Some sewers do light leatherwork on domestic machines or industrial machines for garment with dropfeed.

I found this information about feed timing from JUKI on more of their industrial machines for garment:

So they recommend an advance in feed timing in order to reduce variations in stitch length. A reason might be that the thread tension is applied and stitch is formed after the stroke of the feed dog finished. Therefore thread tension do not work against the feed.

What is new to me is, that JUKI propose a delay in feed timing to increase stitch tightness. In this link it is reported, that you can reduce seam pucker by retarding feed timing:

Link to book, Joining textiles

I think it can be so, that with delayed feed timing, the feed is part of forming the stitch and makes some of the local thread tension to do so. Therefore less thread tension is needed from the tensioners. The result is that you can reduce seam pucker. But with heavier fabrics or more firm fabrics seam pucker will never be a problem and therefore it can be better to advance timing to improve feed dog traction with such fabrics.