Machines might seem boring and mundane things—dirty and noisy and full of fuss—but just trying imagining life without them. Take
sewing machines, for example. Without those tireless, automatic cloth
stitchers, thumping their needles up and down all day long, you
wouldn't have all those fancy clothes in your wardrobe, and the
ones you did have wouldn't be anything like as decorative or
cheap. Modern fashions and textiles can be fabulously arty and
creative, but they depend on surprisingly humdrum bits of engineering:
electric motors; cranks and cams; wheels, gears and levers—the kind
of clanking metal bits and bobs more at home inside a car! So
why does a sewing machine need all this stuff inside it? Let's take a closer
look!
Photo: A typical Singer electronic sewing machine. Singer has been one of the most popular makes since the 1850s, when Isaac Singer patented his first machine.
Remember when you first learned to sew with a needle and a length
of cotton thread? The technique you used back then (and you probably
still use it for simple hand repairs) is called running stitch.
Suppose you want to join two pieces of flat material together. You
thread a needle with a length of cotton (maybe doubling it up for
strength), press the two pieces of material together, then simply
push the needle through them so it takes the cotton with it. You
pull the needle right through, move it along the material a little
bit to form a stitch, then push it back through the material in
the opposite direction, leaving some of the thread (the stitch)
behind. In this kind of hand sewing, you use a single thread, and the
stitches form alternately on the upper and lower sides of the
material.
If that's your idea of sewing, you've probably never quite been
able to figure out how a sewing machine works. If it keeps raising
and lowering its needle, how can it possibly pass the thread back and
forth without getting all tangled up? If the needle pokes the thread
down through the material and then pulls it straight back up again,
how does a stitch form at all? Isn't the stitch getting undone when
the needle comes back up? It just doesn't make any sense!
This problem challenged many inventors during the 19th century,
who struggled with ways of mechanizing the process used by a skilled
human seamstress. It's easy to see how a robot arm could sew running stitch, because it
could just hold a needle the same way you do and repeat exactly the
same motions. But an ordinary sewing machine clearly can't stitch
that way because it never "lets go" of the needle, pushes it
right through the material, or reverses its direction. And, in any
case, they didn't have robots in those days!
Artwork: Running stitch, used for hand stitching, is almost impossible to do with a sewing machine, because it involves constantly removing the needle from the material and reversing direction.
So the secret behind sewing machines is that they work a totally
different way, using a different kind of stitch and two totally separate
threads, one fed from above (by the needle) and a second one fed from
below (by a reel called a bobbin mounted in a rotating carrier called
a shuttle). The needle pushes the thread down through the material,
forming a loop that catches on a hook on the shuttle. The loop wraps
around the bobbin thread as the needle pulls the next section of
thread back up through the material. So what the needle is actually
doing is repeatedly feeding thread down through the material to form
successive stitches. This kind of automatic stitching with two
threads instead of one is called lock stitch.
Photo: The shuttle and bobbin live in a drawer that slides open just beneath the presser foot.
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What is a sewing machine?
A sewing machine is, obviously enough, "a machine that sews,"
but if you think about those words literally, it can help you figure
out how it works. Let's say we had a big construction set with
standard, snap-together, engineering components in it; which bits
would we need to make a sewing machine? The answer is surprisingly
few.
Although you can still find the odd hand-powered sewing machine
(and you can operate any machine slowly by hand if you want to for
slow, precision work), virtually all modern sewing machines are
electric: they're built around quite hefty
electric motors (roughly
the same size as the ones you find in vacuum cleaners and lawn
mowers). Pushing a tiny little needle up and down through multiple
layers of thick fabric is hard work; and lifting and feeding the
fabric takes effort as well. If you've ever sewn something like a
pair of curtains, you'll know it can be quite exhausting
turning and moving the fabric, but a sewing machine helps you do that
job as well.
The beating "heart" of a sewing machine is the electric
motor, which is hidden inside the main stem of the machine
usually quite near to the place where you plug in the power cord. The
motor drives three separate mechanisms that are very carefully
timed to cooperate with one another. Two of them, a mixture of
cams and cranks, operate the feed dog, that
little set of teeth that pop up and down just beneath the needle and
the presser foot (which holds the material in place); one
pushes upward against the material (to grip it) and the other moves
it forward by an adjustable amount (to make stitches of varying
length). It's actually a rather neat double-act: one of these
mechanisms makes the feed dog go up and down, while the other slides
it back and forth. Meanwhile, another crankshaft driven by the motor
makes the needle rise up and down, while the fourth and final
mechanism turns the shuttle and hook attached to it that
makes the stitches.
Photo: Side view: You can just see the teeth of the feed dog hiding beneath the presser foot, with the shuttle and bobbin in the little drawer at the front. During normal sewing, the drawer is closed.
Until the 1970s, most machines were electrical and entirely
mechanical; today, many are electronic, which means they work under
microchip control, allowing them to make quite complex decorative
stitch patterns with relatively little effort on the part of the
operator (beyond positioning and turning the fabric). Modern machines
have at least one circuit board and (quite often) an electronic
display to help you set things up.
How does a sewing machine work?
I spent a long time thinking about how best to illustrate the
inner mechanisms of a sewing machine and looking at quite a few
artworks other people have struggled to draw. So many moving parts
are packed into such a small space that it can be difficult to figure
out which bit is doing what. The more accurate the drawing, often the
harder it is to understand, and I think it's actually clearer to look at
the key mechanisms separately. These diagrams are
simplifications that give you a general idea of what's happening;
they're not absolutely faithful to what's happening and they don't
show what's going on inside any specific machine.
The electric motor rests at the bottom at the opposite end of the
machine from the needle. Using a pulley arrangement, it
drives the large handwheel at the top (the wheel you can turn to
stitch slowly and carefully), which is shown red in these diagrams,
and the main powershaft (gray). Let's look at the three key
mechanisms in turn.
1. Needle mechanism
This is the simplest mechanism of the three. The gray shaft drives
a wheel (blue) and crankshaft (green) that makes the needle (black)
rise and fall. The crank converts the motor's rotary
(round-and-round) motion into the needle's reciprocal (up-and-down)
motion.
Artwork: How a simple crank makes the needle rise and fall.
2. Bobbin and shuttle mechanism
As we'll see in a moment, the shuttle and hook that make
stitches from the needle thread have to rotate somewhat faster than
the needle. So the gray shaft has to turn the shuttle more quickly,
which it can do using gears (or pulleys wrapped round wheels of
different sizes).
Artwork: How pulleys or gears can be used to turn the shuttle (brown), which contains the bobbin (yellow).
3. Feed-dog mechanism
The feed-dog moves the fabric through the machine at a steady
speed, so ensuring stitches that are of equal length. It works
by moving upwards and forwards at the same time, which happens
through two interlinked mechanisms driven off the main shaft. I've
drawn one of them (in the center) as a cam (blue), an egg-shaped
wheel that makes a lever (yellow) rock back and forth, so pulling the
feed dog from right to left and then back again. At the same time, a
second crank mechanism (green and red) moves the feed dog up and
down. When these two movements are synchronized, the feed dog works a
bit like a shoe on the end of an upside-down leg. Normally, a shoe
on your leg moves down and backward, then lifts up and repeats the same movement,
pushing back against the ground so your body moves forward. But a feed dog (with the shoe in effect
pointing upward) moves upward and forward, "walking" the material
through the machine one step (one stitch!) at a time.
Artwork: How two separate mechanisms driven by the main shaft make the feed dog rise and fall and move back and forth.
How does a sewing machine stitch?
These three mechanisms are carefully coordinated so the machine can make
perfect, equal-sized stitches, which is what this simple animation
shows. Here, we're looking side-on at the machine. The top thread
(sometimes called the needle thread) is colored red and pokes
through the eye of the needle (black), while the bottom thread
is yellow and feeds from the bobbin (the yellow circle). The
pieces of material we're sewing together are two different shades of
blue. As you can see, the bobbin sits inside a rotating orange case
(the shuttle) with a hook extending from it. Step by step,
here's how the stitches form.
Artwork: How a sewing machine makes lock stitches with two separate threads.
The needle starts off high and moves down toward the fabric.
Although it's not yet obvious, what it's doing at this point is
feeding a length of the red thread through the material to form the next stitch.
The needle thread is tensioned to stop too much thread pulling off too quickly.
The needle punctures the material, taking the red thread with
it. Notice how the shuttle (under the fabric you're sewing) is rotating and the hook on the end (the
orange line extending upward in frame 2) is approaching the needle
thread.
The needle starts to rise up again but it leaves behind a loop
of the red thread, which is the beginning of the next stitch. The
shuttle hook now passes through this loop and catches on it.
The needle keeps on rising but the main action is happening
down under the material, where the shuttle hook drags the red loop
right around so that it locks around the bobbin thread.
The needle, pulling upwards, tightens the red thread and pulls
it back up off the shuttle hook.
The needle, still pulling upwards, pulls the stitch tight. The
red and yellow threads are properly locked together, and we're ready
for the process to repeat to make the next stitch.
Key parts of a sewing machine
What are the bits and what do they do? There are literally hundreds of parts, many hidden
from view. This photo shows the main things you can see and control as you sew:
Photo: The main parts of a sewing machine.
Slot for needle thread.
Wing nut for loosening and removing needle.
Needle.
Presser foot with feed dog underneath.
Drawer containing shuttle and bobbin.
Stitch length adjustment.
Motor housing.
Hand wheel for precision control and slow-motion sewing.
Stitch type selector.
Stitch control.
Thread tension control.
Who invented the sewing machine?
Like computers,
cars, airplanes, and many other modern marvels,
sewing machines can't be credited to any single inventor. On one
level, they simply automate something very basic and ancient: the
idea of joining textiles together with a loose piece of thread. As
we've already seen, modern machines do this using two separate
threads that lock together—and that idea was probably inspired by
the age-old process of weaving textiles with a loom (a large wooden framework
for making pieces of cloth), where one thread passes back and forth through another at right
angles.
Mechanically, sewing machines are based on an ingenious
combination of wheels (very ancient inventions) with standard
engineering components like cams and cranks
and gears (somewhat newer but still ancient inventions, descended from wheels). Modern machines
get their power from electricity (a 19th-century technology) and
their control and precision from electronics (a 20th-century
development). So you can see that sewing machines were less of an
overnight invention and more of a gradual evolution, with mechanical,
electrical, and electronic components slowly automating the simple
process of joining material together to make it less laborious, more
precise, quicker, and more effective.
Artwork: Elias Howe received a patent for this, the first practical sewing machine, in 1846.
You turn the hand crank (brown, left) to build up steady power in the heavy
flywheel (green). Assorted cams
and cranks make the needle holder (light blue) rock back and forth like a clock pendulum.
This carries the curved needle (orange) and its thread (yellow), fed from the bobbin (red), through the material, which is mounted vertically. The shuttle that passes through the bobbin thread to form the stitches is shown in dark blue, but the mechanism is not easy to see properly from this angle.
Artwork from US Patent 4750: Improvement in sewing-machines by Elias Howe, courtesy of US Patent and Trademark Office.
A brief history of sewing machines and clothing
~30,000 BCE?: Humans make the first clothes from animal skins.
~20,000 BCE?: Felt is compressed from animal wool to make the first textile.
~4000 BCE?: Wool is knitted to make textiles for the first time.
~3000 BCE?: Cotton is first cultivated for textiles in India and Egypt.
~1589: Englishman William Lee (1550–1610) invents a simple frame for knitting wool stockings.
1733: John Kay (1704–1764), another Englishman, revolutionizes weaving by inventing the flying shuttle
(a faster way of passing a shuttle through the warp threads on a loom).
1755: Charles Weisenthal, a German based in London, England, patents a double-pointed needle for mechanical sewing.
1760: James Hargreaves (c.1720–1778) develops a weaving machine called the Spinning Jenny that allows textile workers to produce cloth several times faster than before.
1790: Englishman Thomas Saint patents a basic machine for sewing leather, though it's uncertain whether he ever successfully builds one.
1804: Frenchman Joseph-Marie Jacquard (1752–1834) develops an improved "programmable" loom for weaving complex patterns using punched cards, an idea that plays an important part in the history of computers.
1804: In France, Thomas Stone and James Henderson attempt to develop a machine that can sew like a person.
1810: Balthasar Krems (1760–1813) invents a machine for sewing caps.
1814: Joseph Madersperger (1768–1850) invents an automated "Sewing Hand", which mimics human sewing, but fails to develop it successfully.
1829: Frenchman Barthélemy Thimonnier (1793–1857) builds one of the first successful, practical sewing machines out of wood. For a time, the French government use it to make army uniforms.
1833: Walter Hunt (1796–1859), inventor of the safety pin, builds a lock stitch sewing machine, initially declines to patent it, and later abandons it for fear of putting textile workers out of a job.
Late 18th century: Eli Whitney (1765–1825) helps to make cotton abundant and affordable with the invention of his Cotton Gin, which can process cotton plants faster than ever before.
1845: After years of experimenting, Elias Howe (1819–1867) produces the first truly practical sewing machine,
using two threads and a curved needle, for which he's granted US Patent 4750: Improvement in sewing-machines the following year. Unfortunately, it's a complex machine that sells for US$300 (a fortune in those days), so it's much too expensive for most people to own or use.
1851: Inspired by Elias Howe (and copying some of Howe's patented ideas),
Isaac M. Singer (1819–1867) develops an affordable, practical sewing machine, for which he's granted
US Patent 8294: Improvement in Sewing Machines on August 12. Crucially, he allows customers to buy on "hire-purchase," (a simple "buy now and pay later" installment plan), which makes him fabulously rich.
Photo: A model of an early Singer sewing machine, stamped with the date 1849. With its springs, gears, and levers, and chunky frame, it's very definitely a machine: it looks more like something from a metalworking shop than a textile factory! Photo by Harris & Ewing courtesy of US Library of Congress.
1873: Helen Blanchard (1840–1922) invents the zigzag stitch and makes numerous other improvements to sewing machines.
1877: Joseph Merrow invents the crotchet stitch and overlocking, also founding the
Merrow sewing machine company that bears his name.
1893: Karl Friedrich Gegauf (1860–1926), a Swiss inventor, develops hemstitch; his son forms a company that eventually becomes Bernina in the 1930s.
1933: The Singer company develops the Featherweight, the first portable sewing machine.
1978: Singer announces a computer-controlled sewing machine.
2016: Seattle-based Jonathan Zornow unveils Sewbo, a $35,000 robotic sewing arm that can stitch together
simple things like T-shirts. According to Sewbo, this is "the first time that a robot has been used to sew an entire article of clothing."
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