How can water cut through steel?

Waterjets are tools that use highly pressurized, focused streams of water to cut through metal and other solid materials. Learn more about waterjets in this episode.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house stuffworks dot com, where smart
happens Him Marshall Brain with today's question, how can water
cut through steel? A water jet is a tool used
in machine shops to cut metal parts with a very

(00:23):
high pressure stream of water. As amazing as it sounds,
if you get water flowing fast enough, it can actually
cut metal. Think of a water jet is something with
about thirty times the pressure of the power washer wand
at your local car wash. Power washing a car washes
is an everyday example of a dirt film being cut

(00:44):
off the body, wheels, and tires of an automobile. The
key to cutting metal with water is to keep the
spray coherent. Water jets are able to cut because the
spray is channeled through a very narrow jeweled nozzle at
a very high pressure to keep the spray coherent. Unlike
metal cutters, a water jet never gets dull and it

(01:07):
can't overheat. Low pressure water jets were first used for
mining gold in California in eighteen fifty two. Steam and
hot water jets were used in the early nineteen hundreds
for cleaning. High pressure water jets were used for mining
in the nineteen sixties Abrasive water jets were first used
in industry in about nineteen eighty. In the past, only

(01:31):
one piece of metal could be cut at a time
with a saw or other metal cutting mechanical process. It
was time intensive and expensive. Computer controlled water jet and
abrasive jet cutting are used today an industry to cut
many soft and hard materials. The plain water abrasive mixture
leaves the nozzle more than nine miles per hour. The

(01:53):
latest machines can cut within two thousands of an inch,
and they have jet speeds around mock three. Water jets
can cut lots of different things, including marble, granite, metal, plastic, wood,
stainless steel, and aluminum. A water jet can cut a
sandwich of different materials up to four inches thick. This odorless,

(02:14):
dust free, and relatively heat free process can also cut
something as thin as five thousands of an inch. The
tiny jet stream permits the first cut to also be
the final finished surface of the piece. This single cutting
process saves material costs and machining costs. For example, the
engineer merely gives a gear drawing to the cutting shop

(02:36):
and gets back the finished gear very quickly. Water jets
cut softer materials while abrasive jets are used for harder materials.
The actual cutting is often done underwater to reduce splash
and noise. Faster feed rates are used to prevent the
jet from cutting all the way through the water. Pressure
is typically between twenty thousand and fifty five thousand pounds

(03:00):
per square inch. The water is forced through a tiny
hole in a jewel about one one of an inch
in diameter. For more on this and thousands of other topics,
visit how stuff works dot com, and don't forget to
check out the brain stuff blog on the how stuff
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