This document discusses various measurement tools and techniques. It begins by establishing the importance of measurement in quantifying aspects of science. It then defines metrology as the science of measurement and discusses reasons for measuring. The document goes on to explain sources of measurement error and techniques for reducing error, such as using discrimination that is ten times finer than the tolerance being measured. Various measurement tools are introduced, such as calipers, combination squares, protractors, and vernier calipers. Advantages and disadvantages of different tools and reading vernier scales are also outlined.

1. METROLOGY

2. “
When you can measure what you are
speaking about, and express it in numbers,
you know something about it: but when
you cannot measure it, when your cannot
express it in numbers your knowledge is of
a meagre and unsatisfactory kind;…”
Lord Kelvin,
1883

3. Metrology
 Metrology is
“The science of measurement” Used to
communicate about :
Size
Quantity
Position
Time
Etc.

4. Why Measure
If you can’t measure it:
You can’t make it
If you can’t measure it:
You can’t control it
You can’t manage it
You can’t improve it

5. Measurement Errors
All Dimensional Measurements =
Actual Size +/- Errors
Measurement errors must be controlled
Error = The difference between the
actual size and the measured size

6. Sources of Measurement Errors
 Part
 Operator
 Instruments
 Standard
 Environment

8. Ten-To-One Rule
If
Part Tolerance = 0.01”
Then
Gage Discrimination =0.001”

11. Calipers – The Original Transfer
Instruments

12. Types of Calipers
Simple Caliper Instruments

13. Types of Calipers

15. Line of Measurement-
Outside Caliper

16. Line of Measurement-
Outside Caliper

17. Line of Measurement
- Inside Caliper

18. The Combination Square
 This is one of the most useful of
the steel rule variations. It is
rarely used in any kind of
production inspection. However, it
is used universally in tool and die
making, pattern making, model
and prototype work, and for
machine setup.

19. The Combination Square
 The combination square consists of a blade and a
square head. The most popular is 4 inches long.

20. Square Head
1. It provides a right angle reference
2. It provides a means for transferring
either the measured point or the
reference point for the work to the rule.

21. Square Head
Depth Measurement

22. Protractor Head
 It provides a
convenient means
for checking angles
no closer than 1°. Its
chief advantages are
convenience and
rugged construction.

23. Center Head
 In contrast to the
steel rule method for
measuring diameters,
the center head
method is far more
reliable.

24. Center Head
For layout purposes the
center head provides on
of the most satisfactory
methods for finding the
centers of shafts.

25. Vernier Caliper

26. Vernier Reading
 The Reading steps are as follows
1. Read the number of whole inches one the main scale that appear
to the left of 0 on the vernier.
2. Read the highest numbered graduation on the main scale that lies
to the right of the index(0) on the vernier scale. Read these
graduations as even one hundred mil(0.100, 0.200, etc).
3. Read the highest number of whole minor divisions to the right of
the index. Read these graduations as even twenty-five mil
(0.000,0.025,0.050 and 0.075 in.). Add to the sum of steps one
and two (1.125,1.150 in., etc.).
4. Now find the vernier graduation that most perfectly coincides with
any graduation on the main scale. That is the nearest mil and may
be any whole number from zero to 25(0.000, 0.001,
….0.024,0.025). Add this to the sum of the previous three steps.

27. Vernier Reading

28. Advantages and Disadvantages of
Vernier Scales

29. Practices