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1. Experiment No. 4
Title: Study of Mechanical comparator.
Aim: To study the dial indicator type mechanical comparator and its
application in the inspection.
Apparatus: Dial indicator, stand for mounting and testing, test
pieces.
Theory:
1.Introduction of mechanical comparators:
Mechanical comparators are used for the inspection of
components in large numbers at a very fast rate and precisely.
Comparators are used only for comparing with limits of the
dimension given by the designer.
In mechanical comparator, sensing and magnification devices
used are of mechanical type only because of which the
magnification obtained is termed as Mechanical magnification.
In mechanical comparators the required magnification is obtained
by mechanical linkages and other mechanical devices, among
which the main types are discussed below:

2. A. Rack and Pinion: Here the measuring spindle is
integral with a rack, engages a pinion which expands
the movement of the plunger by a gear train.
B. Cam and Gear Train: Here the measuring spindle
acts on a cam that transmits the motion to the
amplifying gear train.

3. C. Lever with Toothed Sector: Here the lever with the
toothed sector at its end engages a pinion in the hub of
a crown gear sector which further meshes with a final
pinion to produce indication.
D. Compound Levers: Here levers forming a couple
with pound action are connected through segments and
pinion to produce final pointer movement.

4. E.Twisted Taut Strip: In this, the measuring spindle
movement tilts the knee creating straining which further
forms the twisting taut band to rotate proportionally.
The motion of the strip is displayed by the attached
pointer movement.
F.Lever Combined with Band Wound Around Drum:
In this, the movement of the measuring spindle tilts the
joined block, creating a swing of a fork that causes
rotation of the drum.

5. G. Reeds combined with optical display: In this, the
parallelogram reeds are used to transfer measuring
spindle movement to a deflecting reed whose extension
provides a target used in the optical path
2. Types of Mechanical Comparators:
A. Dial indicator type
B. Johanson’s Mikrokator
C. Reed type
D. Sigma Comparator
E. Brooke’s lever comparator

6. Here we are going to study only dial indicator type mechanical
comparators.
Dial Indicator:
Dial Indicator is the most commonly used mechanical comparator. It
works on the principle of Rack and pinion system i.e., the linear
movement of the spindle is magnified by rack and pinion
arrangement.
It consists of a robust base whose surface is flat and a pillar
supporting a bracket in which a spindle is fitted with a pinion and a
dial scale.
Scale

8. Applications, Advantages, and Limitations: To be
explained by students in their own words.
Procedure: To be explained by students in their own words.
Observation :
1. Least count of dial indicator = ……………….
2. The number of components under observation =
……………….
Observation Table: (Sample calculation to be shown)
Component
No.
Max.
Derivation
On one side
Max. Derivation
On another side
Avg. Derivation
On Component
Mean Derivation of
all observation
1)
2)
3)
4)
5)
Conclusion : Thus we have learned the different type of comparators and
their application