 |
How
They Make Razor Blades Sharp
Every
24 hours, as many as 25,000 hairs grow up to half a millimeter
on the face of the average adult male. The modern razor
blade, honed to perfection, can cut its way through this
stubble forest to give a close, smooth and safe shave.
Men began removing their fast- growing facial hair thousands
of year ago, using slivers of flint and then bronze, and
eventually iron blades. |
The world’s first steel-edged
‘cut-throat’ razors were introduced in Sheffield
in 1680. But the modern type of disposable safety razor
blade did not appear until 1901, when a Wisconsin travelling
salesman, King Camp Gillette, and an engineer, William
Nickerson, were granted a patent.
A razor blade starts its life as a continuous coil of
rolled steel strip about four thousandths of an inch (0.1
mm) thick, about the same thickness as the hair it is
designed to cut.
The steel is an alloy containing about 13 percent chromium,
which gives it increased hardness and resistance to corrosion.
The hardness is increased further by heating the steel
and then plunging it into cool fluid.
The shaving edge is produced by grinding. The strip passes
through three sets of grinding wheels, each grinding finer
than the one before. The wheels are set at different angles
to give what is called a gothic-arch (curved) cross-section.
The shape is stronger than a straight-sided wedge. The
sharpness of the blade is expressed as the radius of the
curve forming extreme tip of the cutting edge: about five
hundred thousandths of a millimeter.
After grinding, the cutting edge is polished by rotating
leather wheels. On a microscopic scale, however, the edge
is still rough and because of friction, liable to snag
the hairs and cause discomfort. To protect the cutting
tip and reduce friction, the blade is given three successive
coatings: chromium, ceramic and the plastic PTFE, more
familiar as the slippery non-stick coating on pans. The
chromium resists corrosion, the ceramic reduces wear and
the PTFE produces lubrication.
The coating are each less than one hundred thousandths
of a millimeter thick.
The razor blade fits into a holder with a handle, which
may be adjustable and may screw, open to take the blade.
|
|
|
How They Make
Clothes To Fit Almost Everyone
The traditional tailor can take account
of long arms or a spreading waistline and achieve
a perfect fit. But made-to-measure clothes get more
expensive every year, and the modern clothing industry
has to make off-the-peg clothes that fit most people
with no alteration.
|
|
One of the first proper surveys into people’s measurements
was carried out by the US Government, who measured 1000 recruits
during the First World War to determine the best sizes for uniforms.
In Britain, 5000 women were measured in the early 1950s, with
some unexpected results. Existing size charts were based on
an average height for women of 5ft 6in (168cm), but the survey
found that the real average was 5ft 3in (160cm).
Today, in large companies, from a basic pattern produced by
a designer, a computer produces a range of sizes to cover the
normal variations of the population. Unusually small or large
people complain that they can never find anything to fit them,
and they are right; it does not make economic sense for manufacturers
to produce the limited number of garments that would be sold.
The next step is to use the patterns to cut out the material
for the garment. Rolls of material, which can be more than 100ft
(30m) long, are laid out perfectly flat by machine. Hundreds
of layers are spread on top of one another so that a large number
of garments can be cut out at once. Computers are used to arrange
the patterns on the material so that the minimum of cloth is
wasted. A paper computer printout, called a marker, is laid
on the layers of fabric ready for cutting. The actual cutting
of the material is done by knives guided from above, or in some
modern factories, by laser beams controlled by computers. The
laser, an intense beam of light, burns a clean cut through the
material, far sharper than the cut of nay knife.
 |
Next, the pieces of material
have to be sewn together. Many operations, such as buttonholing,
can be done automatically. A hand-sewer average 20 stitches
a minute; modern machinery can sew up to 7000 stitches
a minute. Some clothes are not stitched in the traditional
way at all, but fused together. Finally clothes are pressed,
to mould them into the right shape and tomake sharp creases
or pleats. Special presses, called buck presses, are designed
for each part of a garment. |
|
|
|
