The document discusses vernier calipers and micrometers. It describes the basic components and workings of each tool. Vernier calipers use a main scale and vernier scale to take more precise measurements than a simple caliper. A micrometer uses a precisely threaded screw that moves the spindle 0.5 mm with each full revolution. The least count of a micrometer, which is the smallest measurement it can make, depends on the screw pitch and number of divisions on the circular scale. Key parts of a micrometer include the frame, anvil, spindle, sleeve, screw, thimble, ratchet, and various scales.

2. VERNIER CALIPER:-
The simplest method is to read the position of the pointer directly on the scale. When the pointer is between two
markings, the user can mentally interpolate to improve the precision of the reading. This would be a simple
calibrated caliper; but the addition of a vernier scale allows more accurate interpolation, and is the universal practice;
this is the vernier caliper.
1. Outside large jaws: used to measure external diameter or width of an object
2. Inside small jaws: used to measure internal diameter of an object
3. Depth probe/rod: used to measure depths of an object or a hole
4. Main scale (Metric): scale marked every mm
5. Main scale (Imperial): scale marked in inches and fractions
6. Vernier scale (Metric) gives interpolated measurements to 0.1 mm or better
7. Vernier scale (Imperial) gives interpolated measurements in fractions of an inch
8. Retainer: used to block movable part to allow the easy transferring of a measurement

3. LEAST COUNT OF VERNIER

4. PROBLEMS ON VERNIER

5. MICROMETER
A micrometer is a tool used for the precise measurement of very small objects. A micrometer can measure the
depth, length and thickness of whatever object fits between its anvil and spindle. It is commonly used in
mechanical engineering and machining applications.
Working Principle
In a micrometer screw gauge measurements are done actually through a precisely made integrated screw with a
pitch of usually but not necessarily 02 threads per millimeter, which means that on completing exactly one
revolution the displacement achieved is half of a mm i.e. 0.5 millimeter.

6. Least Count.
The least count of screw gauge represents minimum value of a dimension which measurable
hence it actually shows the degree of accuracy to which an instrument can work. The least
count of a screw gauge is represented as:
Least Count = Pitch of the screw / No. Of divisions on the circular
scale
If we are working with the screw whose pitch is ½ mm and the
number of divisions on the circular scale is 50 then, using the
formula stated above least count for our micrometer is going to be
Least Count = 0.5mm / 50 = 0.01mm
This means that we can measure up to the 100th part of a
mm.

7. CONSTRUCTION OF MICROMETER
Frame
The body used to hold the anvil and barrel firmly in their place is
called frame , in micro meter screw gauges , thick C shaped frames
are used . Their mass helps in minimization of expansion or
contraction due to temperature some manufacturers also deliver
gauges with insulated frames to serve the above mentioned purpose.
Anvil
It is the fixed part mounted at one end of frame exactly parallel to the
moving spindle which move towards it , Anvil face which comes
directly in contact to the object being measured is machined
extremely fine so to achieve highest degree of precision.
Spindle
The cylindrical part which displaces by rotation of thimble decreasing
the clearance between itself and anvil until the object being
measured become stable between the two of them , in modern
micrometer screw gauges , anvil and spindle`s open face are tipped
with carbide.

8. Sleeve/Barrel
the stationary part with having linear scale onto it, called the main scale, it also covers the screw mechanism
of screw gauge , now screw gauges are available with adjustable sleeves which makes it easy to eliminate the
zero error.
Screw:-It is the most important part of instrument because all measurement
is done through it in fact. Very fine stainless steel screws are used for this
purpose with a definite pitch.
Thimble:-It is the part through which measuring screw is rotated, this
screwing results in the displacement of spindle and thimble itself.
Ratchet; Ratchet is itself a small device which is used to provide a limited
applied force , It is installed at the right end of screw gauge , ratchet acts as
a safety device for instruments and also adds more precision in
measurement . Final adjustment is made by a making three turns of ratchet.
Locking Device:-It is actually a nut whose operation is facilitated by means
of a lever, usually used to hold tight the spindle at its place so that current
reading of that time could be maintained up to a desired length of time.
Scales:-Micrometer screw gauge comes with two scales, one rotating scale
which can be found on its rotating cylindrical part it is also called circular
scale and the other one can be found on its stationary sleeve which is called
main scale or sleeve scale , some designs of instrument can also have a
vernier scale as well.

9. SOME PROBLEMS