Quiz: Mechanical Engineering
Topic: Metrology and Inspection
Each question carries 2 mark
Negative marking: 1/3 mark
Time: 15 Minutes
Q1. What is the relation between variation due to observation, manufacturing process and measuring process of a product?
(a) σobservation = σprocess + σmeasurement
(b) σobservation = σprocess – σmeasurement
(c) σobservation = σprocess * σmeasurement
(d) σobservation = σprocess / σmeasurement
Q2. Which type of tolerance provided in drilling mostly?
Q3. Which of the following is incorrect about tolerances?
(a) Too loose tolerance results in less cost
(b) Tolerance is a compromise between accuracy and ability
(c) Too tight tolerance may result in excessive cost
(d) Fit between mating components is decided by functional requirements
Q4. What is the principle of ‘The Johansson Mikrokator’?
(a) Button spinning on a loop of string
(b) Principle of interference
(c) Optical magnification
(d) Principle of transformer
Q5. What is ‘IT01’?
(a) Basic size of hole
(b) Basic size of shaft
(c) Tolerance grade
(d) Standard tolerance factor
Q6. What does ‘50’ represents in 50H8/g7
(a) Basic size
(b) Actual size
(c) Maximum limit of size
(d) Minimum limit of size
Q7. What is the use of feeler gauge?
(a) To find the thickness of work piece
(b) To measure the gap width
(c) To check straightness
(d) To check flatness
Q8. Which of the following is incorrect about micrometer?
(a) Thimble and barrel should have a dull finish
(b) Total travel of the measuring spindle is called measuring range
(c) Graduated surface diameter of barrel should be 5 mm
(d) Screw has 10 or 20 threads per cm
Q9. Which of the following is used to make optical flats?
(a) Toughened glass
(b) Glass wool
(c) Fused quartz
(d) Porous glass
Q10. Which of the following is generally used to calibrate slip gauges?
(d) Gap gauge
Sol. The variation in the observation depends upon the variation in the product due to manufacturing process and variation due to measuring process. In order to keep σobservation minimum measurement should be kept minimum so that product as a whole is reliable.
Sol. Mostly unilateral tolerance is provided in drilling as dimension is allowed to vary in one direction only. Hole is always oversize, not undersize.
Sol. Loose tolerance results in increase in cost, assembly problems and poor performance of the product. Tight tolerance results in unnecessary machining and inspection time.
Sol. Johansson Mikrokator is a mechanical comparator used to obtain mechanical magnification. Principle of Johansson Mikrokator is ‘spinning of a button on a loop string’. Magnification of this comparator is of the order of 5000.
Sol. ‘IT’ refers to the standard tolerance which belongs to any standard grade of tolerance. Tolerance grades are designated by ‘IT’ letters followed by a number. For example, IT01 is a tolerance grade.
Sol. 50 represent the basic size of the hole and shaft. H and g are the positions of tolerance zone with respect to zero line for hole and shaft respectively. 8 and 7 are the tolerance size.
Sol. Feeler gauges are used to measure gap width between two parallel faces e.g. finding clearance between two parallel surface.
Sol. Thimble and barrel should have a dull finish for ease of reading. Graduated surface diameter of the barrel should not be less than 10 mm.
Sol. Optical flats are generally made from fused quartz or borosilicate glass as they have the least coefficient of linear expansion. This glass is colourless and free from defects like bubbles, internal strains and extraneous matter.
Sol. As a result of handling in the labs or inspection workshops, slip gauge is responsible for displaying the signs of wearing after the appreciable period of use and therefore, should be checked or re-checked at regular intervals. It can be easily done with the help of millionth measuring machine such as Newall Interferometer.