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Zigzag Stitch Mechanism
Ralph M. Sharaf · Public domain (expired patent)
Tex

Yenziwe ngu-

Tex

22. uMandulo 2026FO
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Zigzag Stitch Mechanism

The lock-stitch machine already published sews a straight line, and a straight line of thread cannot stretch - which is why early machines could not sew knitted cloth, finish a raw edge, or work a buttonhole. The next rung is a mechanism that swings the needle bar sideways between stitches, driven by a cam turning with the main shaft. **US 1,466,150**, "Zigzag mechanism for sewing machines", Ralph M. Sharaf, filed 2. April 1917, granted 28. August 1923: a cam-driven vibration of the needle bar while the machine stitches, with the throw adjustable. Domestic zigzag machines followed in the 1950s. **You build the motion in wood** - a cam, a follower and a pen drawing the needle's path - then sew both stitches on jersey and pull them until something gives.
Ophakathi
3 hours

Imiyalelo

1

Cut a cam

From 18 mm plywood cut a 60 mm disc and drill its pivot hole 5 mm off centre: that offset is half the zigzag width. Cut a second disc with a 10 mm offset for a wider stitch.

Izinto zokwakha zalesi sinyathelo:

Ishidi le-plywoodIshidi le-plywood1 ucezu

Amathuluzi adingekayo:

Isaha SesandlaIsaha Sesandla
Ibhola ElingenantamboIbhola Elingenantambo
IrulaIrula
2

Follower and needle bar

Screw a pivoted arm to the board so one end rides on the cam's edge and the other carries a dowel - the needle bar. A spring keeps the follower against the cam. Tape a marker to the dowel.

Izinto zokwakha zalesi sinyathelo:

Izikulufu zomshiniIzikulufu zomshini4 izicucu
Iqoqo lezintambo zokucindezelaIqoqo lezintambo zokucindezela1 isethi
Izinduku ZokhuniIzinduku Zokhuni1 ucezu
Ipeni ElingesulekiyoIpeni Elingesulekiyo1 ucezu

Amathuluzi adingekayo:

Isibhamu sikaglu oshisayoIsibhamu sikaglu oshisayo
Isibambo SebhentshiIsibambo Sebhentshi
3

Draw the stitch

Pull a strip of graph paper steadily under the pen while turning the cam by hand, one turn per stitch. Measure the width of the trace; swap cams and repeat. Lock the follower to draw a straight line for comparison.

Izinto zokwakha zalesi sinyathelo:

Iphepha LamagridiIphepha Lamagridi1 ishidi
Itheyiphu lokumbozaItheyiphu lokumboza1 umqulu

Amathuluzi adingekayo:

IrulaIrula
4

Sew the real thing

Cut six 200 x 50 mm jersey strips. Join them in pairs with a 100 mm seam: straight stitch, zigzag 3 mm, zigzag 5 mm, all at 2.5 mm stitch length.

Izinto zokwakha zalesi sinyathelo:

Ingxube Yezindwangu ze-jersey ze-T-shirtIngxube Yezindwangu ze-jersey ze-T-shirt1 ucezu
Intambo ye-polyesterIntambo ye-polyester10 amamitha

Amathuluzi adingekayo:

Umshini wokuthungaUmshini wokuthunga
Isikelo sendwanguIsikelo sendwangu
5

Pull until it gives

Mark 100 mm across each seam. Pull each pair apart steadily by hand and note the marked length when the thread snaps - or when it does not, and the cloth simply stretches.

Amathuluzi adingekayo:

IrulaIrula
Ithephu LokulinganisaIthephu Lokulinganisa
6

Thread geometry and your results

Ilayisha incwadi ye-Jupyter…
7

History & Context

**What the patent specifies:** a cam-driven mechanism that vibrates the needle bar laterally during stitching, with adjustable throw. **Modern build (derived):** a plywood cam and follower drawing the path, plus real seams for the test. The same sideways swing gave overcast edges, buttonholes and decorative stitches, and cam stacks later let a machine select a pattern. Its limits: a zigzag uses more thread, can tunnel thin cloth if the tension is wrong, and the needle bar's sideways travel puts a limit on machine speed.
Isinyathelo 7 - Image 1

Izinto

9

Amathuluzi Adingekayo

8

Ama-blueprint ahlobene

Lama-blueprint abelana ngolwazi — amasu, izinto noma izimiso

The Lock Stitch Sewing Machine — Mechanized Garment Construction

The Lock Stitch Sewing Machine — Mechanized Garment Construction

ngu-TexFO

Indwangu Nesikhumba

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