Most Ideal Needle Position for Turning

[WMages]

I first learned to sew in a Batchelor Survival Class in HS and at the time, learned to always turn a corner by leaving the needle down, but on the domestic/commercial machines we used, it was hard to tell exactly where the scarf was at.

Now I use several Leather Sewing Machines including a Weaver Cub, a CB4500, a Seiko CW8b and a Cowboy 797 flatbed. I sometimes run into issues turning in a circle or around some radius edge. I understand that the needle needs to begin its upstroke before the presser foot is raised so that the knot is completed. With my cylinder arm machines, I can visually see the scarf easily. My question with that is is there a sweet spot on where the needle should be on its upstroke or am I overthinking this? Sometimes I accidentally allow the needle to leave the material in my effort to make sure the knot is finished. 

Also, on on sewing vegetan leather layers, say 2" radius, should I lift the presser foot with each stitch? If I do, my feet seem to be swinging like the foot of a pipe organ player. Or, is it ok to just make the radius and not lift the presser foot? I'm sorry so long and I've tried different methods but I'm looking to learn the most accurate and most efficient way to sew around the curves. I admit, I'm guilty in not practicing on scrap pieces. I tend to learn as I go on a project and have wasted more than a few due to a sewing glitch. TIA

[Samalan]

I must admit I've never thought about that other than the needle should be down when making a right-angle turn. But I think the needle needs to come back up about 3/16th of an inch. My machines are set up with eps but I've never had a problem either way. On the 2" round, you should be able to just stitch around that if your machine can go slow enough. That said, my machine is set up with a box-style speed reducer I got from Bob Kovar. Getting that was a game-changer, talk about heavy-duty wow. 

[Constabulary]

I make turns when the needle has risen from BDC and is still inside the material (approx needle eye above or even with needle plate - depending on how thick the material is) this way I know the thread loop is caught by the hook.

Just what I do...

[kgg]

3 hours ago, WMages said:

I sometimes run into issues turning in a circle or around some radius edge. I understand that the needle needs to begin its upstroke before the presser foot is raised so that the knot is completed.

When making a hard turn like a 90 or 180 degree burying the needle and raise the needle about 5 mm so the hook catches the top thread loop then very slightly raise up the presser foot just to remove the tension on the item then slowly turn the item. If you raise the presser foot to much you can accidentally move the item to one side or the other which could cause a slack stitch.  Use the correct needle to thread combination for both your top and bobbin thread as well as the thickness of the item. If the needle hole is to small the top thread can catch on the inside of the hole and twist when you turn the item. Also you should use the same size thread in the bobbin as you are using as a top thread. 

Here is a link to a good thread to needle size chart: https://www.tolindsewmach.com/thread-chart.html

As far as a 2" radius turn slow down or handwheel through the turn. If you don't have a speed reducer you may find slow speed sewing a bit difficult particularly if you are using a brushless servo motor with a high startup speed. A lot of the brushless servo motors have a a high startup speed which can create a sudden speed jump. Installing a 3:1 or better speed reducer which will help smooth out the speed jump and greatly improve your slow speed sewing.

kgg 

[BlackDragon]

If I'm doing a sharp turn I stop as the needle is on the way back up but not out of the leather. This allows me to keep the leather in the correct position when I lift the foot to turn and the position of the needle, on the upstroke and before coming out of the leather, assures me the knot was made.

When doing gentle curves I wait for the upstroke with the needle out of the leather and only the center presser foot making contact with the leather. Waiting for the upstroke means my knot should be made. Only the center foot in contact with the leather means less marking on the leather. If the right or left foot is on the leather when turning there's more of a chance to mar the leather when turning.

[Wizcrafts]

@WMages, You probably can benefit from a spped reducer on some of your machines that are running too fast for precision sewing. Read about them on the Toledo Industrial Sewing Machines website, on the lower portion of the Motors page.

Another adjustment that can help with sewing twists and turns is lowering the foot pressure. The pressure foot's job is to hold the material down flat against the throat plate as the needle ascends. You only need enough pressure to prevent the leather from lifting up as the knots enter the bottom of the leather. Run a test to see how much pressure can be removed before the leather lifts and you get skipped stitches.

[AlZilla]

I haven't had a problem on my machines by bringing the needle up an eyeballed 1/4" from bottom.  Same kinds of machines you're using. 

I can't speak to the 2" radius, I'd have to sit down and actually try it. It seems a little tight.

[Samalan]

27 minutes ago, AlZilla said:

I haven't had a problem on my machines by bringing the needle up an eyeballed 1/4" from bottom.  Same kinds of machines you're using. 

I can't speak to the 2" radius, I'd have to sit down and actually try it. It seems a little tight.

Let's not forget that a 2'' Rad is a 4" Diameter. In my opinion, if you have a properly set up machine, you should be capable of stitching around a 1/4" Rad very easily.

Of course, that's with a speed reducer and ep..s.

[AlZilla]

3 hours ago, Samalan said:

Let's not forget that a 2'' Rad is a 4" Diameter. In my opinion, if you have a properly set up machine, you should be capable of stitching around a 1/4" Rad very easily.

Of course, that's with a speed reducer and ep..s.

Good point. I visualized a 2" pipe in my mind to get a picture. I agree, a 4" circle should be eminently doable.

[WMages]

Thanks for everyone of these replies. I'm fairly adept with geometry but in my haste, I misstated radius and should have said 1" radius. Several comments answered my specific question and also indicates there is some leeway on needle height from BDC. The comment regarding turning when the outer (left or right) foot is lifted along is very helpful. Wiz, regarding presser foot pressure, I've backed it off but am unsure just how far to go. I will explore that farther. I've read your comments elsewhere that someone makes presser foot spring with either less coils or less tension. Regarding speed, My Cowboy 4500 has speed reduction. My Seiko CW8b came to me with a servo motor a bit on the small side. I replaced it with one that is about twice the duty of the first one and it starts smoothly and can sew about as slow as my brain works sometimes, which is very slow. The Seiko doesn't have a speed reduction pulley on it but I find it's speed very workable. I'm just struggling with occasional missed and loose stitches. So much to learn but I'm trying to soak it all in. I've stated before, I have lot more equipment than talent and like with my guitar pedals, I have never found a talent pedal.   Thanks again and a million for all of you taking the time to respond.