Mechanical Engineering : Micrometer and it's Calculation.

Micrometer is use to get accurate measure for a
parts.
it give a high accuracy then vernier calipers!!
vernier micrometer is highly use in Mechanical
engineering operations and also use for final
inspection in inspection section of any productional
industry.

kinds of micrometer : primary Micrometer is 2 parts,
♦ Inside micrometer.
(it is use to take। internal dia of any internal hollar
job)
♦ outside micrometer.
( Outside micrometer is used to determine accurate
outside Dia of any diagonal and circular job)
in industry Outside micrometer is mostly used.
By outside micrometer internal Dia also can be
taken.
then a extra parts need with original
Micrometer.
It is called Telescopic gauge.

Telescopic gauge: Telescopic gauge is use to
compare measurement between micrometer and
internal holed job. and help to take same and right
measurement.

Full calculation : Micrometer
The micrometer is an instrument used for the
accurate measurement of short lengths. It
consists essentially of a carefully machined
screw mounted in a strong frame. The object
to be measured is placed between the end of
the screw and the projecting end of the frame,
called the anvil. The screw is then advanced
until the object is gripped gently between the
two jars of the instrument. Most micrometers
are provided with a ratchet which is arranged
to slip on the screw as soon as a light and
constant force is exerted on the object. By
using the ratchet it is possible to tighten up
the screw by the same amount each time, and
thus avoid using too great a force. If this
arrangement is absent, great care should be
taken not to force the screw, for the
instrument may be easily damaged.
The micrometer used in this lab consists of a
screw with a pitch of 0.5mm, a longitudinal
scale engraved along a barrel containing the
screw, and a circular scale engraved around a
thimble which rotates with the screw and
moves along the scale on the barrel. The
longitudinal scale is divided into millimeters.
The circular scale has 50 divisions. Since the
pitch of the screw is 0.5mm, which is the
distance advanced by the screw on turning
through one revolution, it is clear that rotating
the thimble through one scale division with
cause the screw to move a distance of 1/50 of
0.5mm, or 0.01mm. Hence, readings may be
taken directly to one hundredth of a
millimeter and better by estimating part of a
division.
The reading of the micrometer is taken by
noting the position of the edge of the thimble
on the longitudinal scale and the position of
the axial line of the barrel on the circular
scale, and adding the two readings. The
reading of the main scale gives the
measurement to the nearest whole main scale
division; the fractional part of a main scale
division is read on the circular scale. Since it
requires two revolutions of the screw to make
it advance a distance of one millimeter, it is
necessary always to be careful to note
whether the reading on the circular scale
refers to the first half or the second half of a
millimeter. The micrometer in the diagram
here is reading 7.75mm.
The micrometer should be checked for a zero
error, for it may not read zero when the jaws
are completely closed. In such cases a zero
correction has to be applied to every reading;
this correction may be either positive or
negative. The value of the zero reading is
obtained by rotating the screw until it comes
in contact with the anvil, and then noting the
reading on the circular scale.