This document discusses and defines various mechanical engineering measuring instruments and gauges. It begins by distinguishing measuring instruments, which can measure dimensions adjustable to 0.001mm, from gauges, which have fixed dimensions. It then provides descriptions and uses for 14 specific measuring instruments, including vernier calipers, height gauges, depth gauges, ring gauges, plug gauges, and micrometers. It concludes by defining tolerance as the difference between upper and lower dimension limits, and upper and lower deviations.

1. Top 20 Interview Questions
On
Mechanical Engineering Measuring Instruments & Gauges
Measuring Instruments & Gauges
The measuring instruments are the devices which are used to
measure the exact size and dimensions of an object. These are also called as
Dimension control Instruments. These are the adjustable devices which can
be measure up to 0.001 or better.
Where as in case of Gauges these are the fixed dimensions
instruments. In most cases, these doesn't have adjustable member for
measuring varying dimensions of lengths and angles.
Let’s discuss about some Measuring Instruments and
Gauges:-
1. Vernier Caliper:-
Vernier Caliper is an instrument which is used to measure to external
as well as internal dimensions of an objects like shafts, thickness of any
objects, depths of holes and slots. A Vernier scale on caliper may have a
least count of 0.02 mm while a micrometer have least count of 0.001 mm.

2. 2. Vernier Height Gauge:-
As its name says that it is mainly used to measure the heights of parts
to an accuracy of 0.02mm.
3. Vernier Depth Gauge:-
The Vernier Depth Gauges are used to measure the depth of the holes,
recesses, and distance from plane surface to a projection, to an accuracy of
0.02mm.
4. Ring Gauge:-
The Ring Gauges are mainly used to check or measure the diameter of
shafts or studs.
5. Plug Gauges:-
The Plug Gauges are used to check the accuracy of hole. In
engineering sectors like manufacturing companies, tool rooms, workshops
the Standard Plug Gauges very important Instruments. The limit plug
gauge is used where the large quantities are produced. The single -ended
plug gauges limit plug gauges has separate Go & No Go members. The
progressive limit plug gauges has Go&No Go members on the same side of
a handle.
6. Snap Gauges:-
Snap Gauges are used to measure the external dimensions of object.
7. Slip Gauges:-
Slip Gauges are also known as Gauge Blocks. Gauge blocks come in
sets of blocks with a range of standard lengths. These are generally used to
check or measuring the linear dimensions very accurately.
8. Feeler Gauge:-
The Feeler Gauges are used to check the clearances between the two
mating surfaces.
9. Inside Micrometer:-
Inside Micrometers are generally used to measure the large internal
diameter about 50mm with an accuracy of 0.01mm.

3. 10. Outside Micrometer:-
It is used to measure the outside of an objects diameter or length of a
small parts with a accuracy of 0.01mm.
11. Screw Thread Micrometer:-
It is used to measure the pitch diameter of screw threads with an
accuracy of 0.01mm
12. Depth Gauge Micrometer:-
Depth Gauge Micrometers are used to measure the depth of holes,
slots and recessed areas with an accuracy of 0.01mm.
13. Combination Set:-
The Combination set is a very important instrument and has all the
essential features of try square, bevel protractor, rule and scriber.
14. Universal Bevel Protractor:-
The Universal Bevel Protractors are the instruments which are used
to measure the angles with the limits of 5minutes (1/12 of a degree).These
are also called as Vernier Bevel Protractors.
15. Sine Bar:-
These are used either to measure angles more precisely than bevel
protractors or for locating any work to a given angle within very close
limits.
16. Scribing Block:-
The Scribing Blocks are used to locate the centers of round bars.
17. Surface Plate's:-
Surface plate's which are used to check the trueness of Flat Surface.
18. Tolerance:-
It is defined as the difference between the Upper Limit and Lower
Limit of a dimensions.

4. 19. Upper Deviation:-
The algebraic difference between the maximum limit and the basic
size is called as Upper Deviation.
20. Lower Deviation:-
The algebraic difference between the minimum limit and the basic
size is called as Lower Deviation.
-By
Pranav Harke