2. Metrology
Metrology is the science of measurement. It includes all theoretical and practical aspects of measurement.
It is derived from Greek word metros which means “measure”.
Should not be confused with meteorology which deals with study of the atmosphere that focuses on weather processes and climate forecasting.
The subject of metrology has changed since the introduction of concept called Interchangeable parts by Eli Whitney.

3. Tolerances
Courtesy: ANSI/ISO

4. Tolerances
Courtesy: ANSI/ISO

5. Tolerances
Courtesy: ANSI/ISO

6. Tolerances Price ? Rs 30 Roundness 25 µ Rs 200 Roundness 5 µ

7. Tolerances
Clearance Fit

8. Geometric Tolerances

9. Geometric Tolerances

10. Geometric Tolerances

11. Geometric Tolerances

12. Geometric Tolerances A B B as a Datum, Parallelism = 0.05 mm A B
A as a Datum, Parallelism = 0.02 mm

13. Geometric Tolerances
Courtesy: ANSI/ISO

14. Accuracy & Repeatability
100 shafts of diameter 50 mm were manufactured using different manufacturing processes.
When manufactured by process A the diameter of shafts were in the range of to (Accuracy=0.006)
When manufactured by process B the diameter of shafts were in the range of to (Accuracy=0.024)
Process A has better accuracy than Process B
When manufactured by process C the diameter of shafts were in the range of to (Accuracy=0.021)
Process C has better repeatability than Process A
Accuracy and Repeatability

15. Accuracy & Repeatability
Accuracy and Repeatability

16. Accuracy and Resolution
Shafts Y and Z of diameter 50 mm manufactured using a process were measured using three different instruments.
Shaft Y Shaft Z
Steel Rule mm mm
Vernier Caliper mm mm
Micrometer mm mm
Resolution of steel rule is 0.5 mm, vernier is 0.01 mm and micrometer is mm.
Accuracy and Resolution

17. Metrology
Shafts of diameter 50 mm were manufactured using a process and needs to be inspected for meeting tolerances.
Micrometer (Option A)

18. Mechanical Comparator (Option B)
Metrology
Mechanical Comparator (Option B)

19. Metrology =
75 +
1 +
1.3 +
1.05 +
1.002
Slip Gauges

20. Snap Gauge/Go-Nogo Gauge (Option C)
Metrology
Snap Gauge/Go-Nogo Gauge (Option C)

21. CMM – Coordinate Measuring Machine
Cylindricity
Flatness
Roundness
CMM – Coordinate Measuring Machine

22. CMM
Flatness – 6
Parallelism – 3
Squareness – 12

23. CMM – Coordinate Measuring Machineyi
y = a + bx
a + b xi
ei = yi – (a + b xi )
CMM – Coordinate Measuring Machine

24. Straightness

25. Straightness

26. Straightness

27. CMM – Coordinate Measuring Machine