micrometer screw gauge
DESCRIPTION
Introduction to PhysicsTRANSCRIPT
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1.RAHAZIMAH ALZAHRAH ABU BAKAR SADIQIN
2.SITI AISHAH KHADIJAH
3.INDERJIT KAUR
4. KHAIRUL AIN
5. FARRALISA MAISARA
MICROMETER SCREW
GAUGE & METRERULER
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HISTORY
The word micrometer is a neoclassical coinage from
Greek micros, "small", and metron, "measure".
The first ever micrometric screw was invented by
William Gascoigne in the 17th century, as anenhancement of the vernier; it was used in a telescope
to measure angular distances between stars and the
relative sizes of celestial objects
The first documented development of handheld
micrometer-screw calipers was by Jean Laurent Palmer
of Paris in 1848;[2].
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Basic types
The topmost image shows the three most commontypes of micrometer; the names are based on theirapplication:
Outside micrometer(aka micrometer caliper), typicallyused to measure wires, spheres, shafts and blocks.
Inside micrometer, used to measure the diameter of
holes.
Depth micrometer, measures depths of slots andsteps.
HISTORY
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PARTS
A micrometer is composed of:
Frame
The C-shaped body that holds the anvil and barrel in constant relation to each other.
It is thick because it needs to minimize flexion, expansion, and contraction, which
would distort the measurement.
The frame is heavy and consequently has a high thermal mass, to prevent
substantial heating up by the holding hand/fingers. It is often covered by insulating
plastic plates which further reduce heat transference.
Anvil
The shiny part that the spindle moves toward, and that the sample rests against.
Sleeve / barrel / stock
The stationary round part with the linear scale on it. Sometimes vernier markings.
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Lock nut / lock-ring / thimble lock
The knurled part (or lever) that one can tighten to hold the spindle stationary, such
as when momentarily holding a measurement.
Screw
(not seen) The heart of the micrometer, as explained under "Operating principles".
It is inside the barrelSpindle
The shiny cylindrical part that the thimble causes to move toward the anvil.
Thimble
The part that one's thumb turns. Graduated markings.
Ratchet stop
(not shown in illustration) Device on end of handle that limits applied pressure byslipping at a calibrated torque.
http://en.wikipedia.org/wiki/Micrometerhttp://en.wikipedia.org/wiki/Micrometer -
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MICROMETRE SCREW GAUGE
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http://www.google.com.my/url?sa=i&source=images&cd=&cad=rja&docid=v-dsTvfpZgtDSM&tbnid=WvjNKUA0RCiSzM:&ved=0CAgQjRwwAA&url=http://www.cyberphysics.co.uk/practical/skills/micrometer.htm&ei=4JAtUbf5H8X_rAfCl4CYDQ&psig=AFQjCNE9rIEWbDYt10eoaNHUiP-nispLmw&ust=1362027104560464 -
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SCALE
MAIN SCALE: A scale marked on sleeve
THIMBLE SCALE: A scale marked on the thimble
1.When taking reading,the thimble is turned until the object is gripped
gently between the anvil and spindle.
2.The ratchet knob is turned until a click sound is heard.The rachet
knob is used to prevent the user from exerting too much pressure on
the object.The grip on object muct not be excessive as this will effect
the accuracy of reading.
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HOW TO TAKE READING
Main Scale Reading
Read main scale reading at the edge of thimble.Take note that an additional half scale division(0.5mm)must be included if the mark below the harizontal refrence line is visible.
Thimble Scale Reading
Read the thimble scale reading at point where the hOrizontal refrence line of the main scale is
in line with the graduation mark on the thimble scale
MAIN SCALE READING+THIMBLE SCALE READING
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ERRORS
Zero error
Zero error is any nonzero reading when the jaws are closed. It is
the calibration error of the deviceoften caused by knocks oroverstrains.
The way to use a micrometer with zero error is to use the formula'actual reading = main scale + micro scale (zero error)'.
"Positive zero error" refers to the fact that when the jaws of themicrometer are just closed, the reading is a positive reading awayfrom the actual reading of 0.00mm. If the reading is 0.15mm, thezero error is referred to as +0.15mm.
"Negative zero error" refers to the fact that when the jaws of themicrometer are just closed, the reading is a negative reading awayfrom the actual reading of 0.00mm. If the reading is -0.09mm, thezero error is referred to as -0.09mm.
CORRECT READING=ACTUAL READING-ZERO ERROR
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MICROMETRE SCREW GAUGE
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Metre RulerMeasure length, distances, degree and
determine straight lines.
Also known as line gauge / rule.
Sensitivity: 1mm
Precautions when using the ruler
Make sure that the object is in contactwith the ruler.
Avoid parallax error.
Avoid zero error and end error.
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DESK RULER
measuring, drawing straight lines and as
guides when cutting with blades.
Have measurement markings along each side;
generally, inches are marked on one side and
centimeters are marked on the other.
Standard desk rulers measure 12 inches or 30
centimeters long.
Manufactured from a number of different
materials, such as wood, plastic or metal, and
are available in clear or opaque varieties.
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LINE GAUGE
used by printers that resemble desk rulers, but
are marked in points, picas, agates and inches.
Line gauges are made of stainless steel and
have engraved markings.
Generally 72 picas or 11.952 inches long