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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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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