S And Z Twist For Hand Sewing Revisited

[bkm]

It is commonly understood that single need machines are to be used with Z twist cables, and that S twist or reverse twist cables are for double needle machines.

In this topic, it was advocated to use S twist for right hand sewers and Z twist for left hand sewers.

http://leatherworker.net/forum/index.php?showtopic=19465

The subject was revisited in this topic:

http://leatherworker.net/forum/index.php?showtopic=56618&hl=%2Bleft+%2Btwist+%2Bright

I am sure the leather and stitching have no way of revealing the dominant hand of the sewer, but only their technique. I am right-handed, but I can just as easily insert the right needle first. I can use the awl in my left hand, or I can just flip the leather over and insert the awl from the other side. In either case, nothing reveals which hand I used, if not both.

What does apparently make a difference is which needle is in front and which is in back, and subsequently whether the cable coming from one side passes over or under the other cable. If a right handed person inserts the needle from the left first and commences a procedure to hand sew, they may end up with cables laying the opposite of a left hander beginning with the right needle and following the same procedure. The procedures that determine the cable lay need to be considered by both right and left hand people so that the cable lay matches the diamond awl or pricking iron pattern and is suitable for the piece being sewn.

I am convinced the hand sewer needs techniques for straight stitching as well as both right (S) and left (Z) hand cable lay. This is one of the reasons we have reverse pricking irons. I sew strap ends -- in fact that is the only leatherworking experience I have. If I sewed both sides of the strap with Z twist stitching they would look asymmetrical like this:

\ \

\ \

\ \

I want to use both S and Z twist stitches so they look like this

/ \ \ /

/. \ \ /

/ \ or \ /

While it is probably only a matter of attention to extreme minutia, the twist of the cords in the cable should tighten with the coil of the stitching, so it should be opposite of the cable lay. Furthermore, the fiber twist should be opposite again of the cord twist.

The simplest way to demonstrate this to yourself is to take a short length of cable and over-twist it, and bring the ends together. It will twist itself opposite. Again, take a piece of common Z-twist cable, hold an end in each hand and over-twist it to the left (counterclockwise with your right hand), and then bring your hands together. The cable will twist itself in S-twist.

Now concerning sewing again, if the cables are layed in S twist, the cords should be Z twist, and the fibers in S twist.

So for Z stitching that looks like:

/

/

/

/

S twist cable should be used, where the cords are twisted right, and the fibers in each cord are Z twisted to the left.

For stitching that looks like

\

\

\

\

Z twist cable should be used, where the cords are twisted left, and the fibers in each cord are S twisted to the right.

Most machine cable has S twisted fibers, and Z twisted cords. You can probably twist your cable the way you want with the cords on your thigh but to set the fibers in the cords, you would need to spin them that way.

For straight stitching like this

|

|

|

|

|

| the cable twist cannot make a difference except possibly at the loop end where the cable reverses direction. But for a double-row of this stitching, the pattern should be given attention:

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

vs vs

Edited April 15, 2015 by bkm

[bkm]

I have modeled a strap with a double row of Z stitching, Z and S, S and straight. The choice of S or Z twist cable can be made based on the type of stitching done, rather than which hand is dominant for the sewer. So if one is making Z twist stitching, S or Right twist cable can be selected. Whereas if one is making S twist stitching, Z or Left twist cable can be selected. The lay of the cable should be determined by the work. For a double-stitched strap end, I use Z and S -- as shown in the model in the middle.

The way a diamond awl is oriented should also be considered. I have made a crude example in construction paper.

Edited April 15, 2015 by bkm

[electrathon]

The angle of the slot or the right or left handed person is not relevant. The reason for left and right twist thread on a machine is solely because the needle/hook/bobbin loops the thread as it sews. When hand sewing this does not happen. Tugging the thread to the left or to the right are not the issue. Twisting the thread clockwise or counterclockwise (done by the machine, not by hand) is the total issue.

[Galloways]

I have modeled a strap with a double row of Z stitching, Z and S, S and straight. The choice of S or Z twist cable can be made based on the type of stitching done, rather than which hand is dominant for the sewer. So if one is making Z twist stitching, S or Right twist cable can be selected. Whereas if one is making S twist stitching, Z or Left twist cable can be selected. The lay of the cable should be determined by the work. For a double-stitched strap end, I use Z and S -- as shown in the model in the middle.

The way a diamond awl is oriented should also be considered. I have made a crude example in construction paper.

Very intuitive, alas it's very late here and I don't have time to explain fully I'll post again in a couple of days with a full explanation of traditional hand stitching with hand spun thrum in right single spun ply and left double spun cable with some pictures but you are on the right path hand stitching and every thing to do with it is ALL IN THE TWIST! while you wait spend your time with a back stitch single needle that's where you need to start and sew with the long back stitch in opposite slopes it'll show instantly that there is a right and wrong way it's nothing to do with being right or left handed, I'll leave you with a couple of pics of real traditional English saddle stitching on a harness pad sewn in hand spun thrum (un dyed linen yarn) at 16 spi, and still fit for purpose after over one hundred years of service.

[bkm]

I have read mentioned in the topics linked in the first post about "throwing the back loop." Throwing the back loop results in an S twist stitch. Passing the needle from the right over the loop on the left results in a Z twist stitch. I alternate these techniques depending on which edge of a strap I am sewing.

I have also read mentioned in the topics linked in the first post, and in related tutorials of a technique to pass the needle through the loop to form an overhand knot in each stitch. I have a made a model of what I believe the result of this technique is. I do not believe this increases the strength of the stitching. Knotting a cable does not increase its strength. There are, of course, many other types of stitching, such as chain-stitching, which may have decorative purposes.