When to stop and turn the material

[Uwe]

Perhaps I'm missing something. I've been wondering for a while now why I keep coming across variations of "A good time to stop and turn the material is when the needle has come back up a little bit." Even Al Bane says something to that effect in one of his videos. That guideline just goes against my understanding of the stitch cycle.

Generally, folks stop to make a turn while the needle is buried in the material because it provides a good pivot point. In that situation it seems to me that the only really BAD time to stop and turn is when the needle has come back up a little bit, the thread is still busy forming a loop but the hook has not yet caught that loop. Thou shalt not mess with the loop, in commandment speak. 

So why do so many folks recommend to stop and turn the material exactly during that most vulnerable period? Is it the thrill of playing Russian roulette with skipped stitches?

In my mind, a good time to stop and turn the material is either:

A.) While the needle is still going down

OR 

B.) AFTER the needle has come back up again far enough so that the hook has had a chance to positively catch the loop.

I really am curious about the reasoning behind the common recommendation and I'd love to hear from others.

Edited June 17, 2016 by Uwe

[dikman]

Uwe, I've wondered this too. The last time I had to regularly stop and turn material I was sewing an "infiniti" pattern on a gunbelt using my Pfaff 335. Every now and then I would get a dropped stitch and couldn't figure out why (it was always at the turning point). I've been pondering this for quite a while, trying to visualise the hook/needle operation when stopping. The only answer I could come up with is that sometimes the needle may have been on the upstroke and turning the material twisted the thread and prevented the loop forming properly. With this in mind I figured it's better to stop right at the bottom of the downstroke, before the loop can form (although stopping on the downstroke, as you say, also makes sense).  Don't know if I'm right, but it sort of makes sense to me.

I shall await, with interest, comments from the more knowledgeable here.

[Wizcrafts]

I recommend making every adjustment a machine is capable of to obtain the strongest loop possible. This includes trying different settings and tensions on the check spring and fine-tuning the timing of the hook. It must also take into account any unusual twist the thread might have, such as in double dyed black bonded nylon thread. With a maximized loop the needle can be just raising from pickoff time as you lift the feet and turn the material.

My Union Lockstitch machine used to drive me crazy by routinely dropping the loop after picking it off the barbed needle, on hard right, but mostly left turns.

[Wizcrafts]

If one is experiencing dropped stitches, one should remove the throat plate and observe what the heck is going on with the loop. The loop might be too small, or might twist away from the approaching hook. I've had situations where a particular needle and hook timing led to too much of the loop forming on the left side of the eye of the needle. The hook that was approaching on the right had a hard time getting enough thread loop to pick off. Sometimes a smaller needle cures that problem. Other times the check spring needs to be readjusted. Still other times, the needlebar may need to be raised slightly so the forming loop clears a cutaway on the left side of the shuttle (meant to aim the loop towards the hook).

[Constabulary]

Seems to depend on the machine and hook a little bit. On my 133K3 the best needle position for a turn seems to be when the needle is on the way up and almost leaving the material / the tip is still inside the material. My 111G156 and 307G2 do not have these problems at all.

Basically I think the best needle position is all the way down (BDC) before the loop has been formed or when the stitch has been almost completed and the needle tip is still inside the material. But thats just a rough guess. But my 133K indeed acts a bit different...

[RockyAussie]

OK this driving me mad now. I don't often get this problem. I went and checked a couple of my machines and the vari stops are set to stop just as the needle is coming up a bit. If i twist the leather around a lot the thread can come out of the needle groove and I get a very small pull to the bottom. Then I tried just putting the needle barely in but enough to spin the leather about quite safely and no problems at all. I noticed that the thread tension check spring is under tension at this point but lifting the feet did not effect it. Maybe that might be a safer way? I respect all of your feedback and look forward to your thoughts.

[dikman]

Rocky, having the needle barely in the material on the downstroke also makes sense, although timing it might be a little more critical. Ensuring the thread is taut when twisting the leather is probably very important, as I'm sure what you describe was happening to me. I'll have to do a bit of experimenting now that I've got some ideas where to start.

I wonder if it makes a difference whether the shuttle/hook is horizontal or vertical?

[Colt W Knight]

I cant turn the material as the needle is entering the leather on the down stroke because turning the leather in this position will deflect the needle sideways which will eother caise the needle to break of the finish downstroke, shred the thread or drop a stitch. 

[graywolf]

I guess, I have not read as widely as I thought, because, I have never seen it recommended that you pivot your work after the needle has started to rise. Even in light fabric, I have always found that is a sure way to drop a stitch. While I have never sewn heavy leather like you guys do, I would think that it would be even more of a problem.

I am with Uwe on this, messing with your loop is a bad thing. After all that is the most critical point in the sewing cycle.

If you do not know how the rotating hook actually works, check out this from the rotating hook wiki.

As you can see from the bottom up is where all the action is. however that wiki is slightly off, because the loop forms slightly after the needle starts to rise while the wiki makes if look like the hook just grabs the thread from the needle. It actually grabs the loop that is formed when the needle starts to rise. Anything that makes the hook miss that loop is going to cause a missed stitch.

Also anything that keeps that thread from being pulled up is going to cause a mares nest under your work or in the bobbin area. So, that is why I say everything from when the needle starts to rise is critical, and stopping the up cycle can cause problems.

[mikesc]

I always turn after the needle has entered, and pierced all layers , but well before the rise begins..made more sense that way, for all the reasons given in posts above..

Edited June 17, 2016 by mikesc