Metrology and Precision instruments - Mechanical Engineering Interview Questions

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21. What is a Gear tooth Vernier caliper?

Gear tooth Vernier caliper id made with vertical and horizontal scales. So movement can be taken at a time with these two scales. It is used to measure the chordal addendum and chordal thickness of a gear tooth within the accuracy of 0.02 mm or 0.001”.

22. State the uses of a Dial test indicator?
  • To check the parallelism of machined or ground surfaces.
  • To check the true rotation of round jobs.
  • To compare the dimensions of finished components.
23. What are the functions of a Comparator?
  • The components can be checked quickly during mass production.
  • For the inspection of newly procured gauges.
  • In selective assembly of parts where parts are graded in groups depending up on their tolerances.
  • As laboratory standard where working and inspection gauges set and correlated.
  • Attached with some machines which can be used as working gauge to prevent work spoilage and to maintain required tolerances at all stages of manufacturing.
24. Explain about an Optical flat?

It is a circular piece of glass or fused quartz with its two plane faces flat and parallel and the surfaces are finished to an optical degree of flatness, Optical flat ray in size between 25 and 300 mm diameter. Quartz flats have high of wearing quality than the optical glasses and have minimum expansion of heat. When an optical flat is placed over a flat surface being measured, a series of rainbow bands are observed which are known as interference bands. Better results can be obtained under colored light because bands are more clearly visible. The optical flats are used for testing the flat surfaces of engineering instruments.

25. What is a gauge?

A Gauge is a checking instrument which is commonly used in tool room and machine shop for checking the finished components.

26. Point on the advantages of Gauges?

  • It increases the production.
  • It saves the time.
  • It makes the parts interchangeable.
  • It reduces the supervision charges.
  • It minimizes the production cost.

27. What is the difference between Workshop gauges and Inspection gauges?

  • Work shop Gauges are generally used in workshops to inspect the job within an accuracy of 0.025 mm. Semi skilled workers are the beneficiaries.
  • Inspection Gauges commonly used to check up more accurate components and also inspect the workshop gauges within an accuracy of 0.0025 mm.

28. Discuss the function of a Feeler gauge?

A feeler gauge is used to measure the gap between two mating parts.

29. Mention the use of ‘GO’ and ‘NOT GO’ plug gauges?

These gauges are used to check the hole dimensions in limit. The high limit end of this gauge should not go in to the hole which is called NOT GO and the low limit end should go in to the hole which is called GO end.

30. What are the benefits of a Gauge block?

  • To check the accuracy of precision instruments.
  • Gauge blocks are also used along with sine bar for setting dimensions to the required heights to read the angle.

31. Clarify the term ‘Wringing of slips’?

The method of twisting the gauge blocks while setting it to required height is known as Wringing of slips.

32. What are the precautions to be taken while using Slip Gauges?

  • The slip gauges must be kept separated, cleaned, and dust free when not in use.
  • Do not keep the slip gauges in a magnetic field, keep out from temperature fluctuations and should not be exposed in dampness.
  • Avoid the contact between the slip gauges for a long time.
  • Functional surfaces must be secured from scratches and hand or finger contacts.
  • Use only linen cloth or chamois leather for cleaning purpose.

33. What is Sine bar, and why it is called as sine bar?

  • A sine bar consists of an accurately finished steel bar having two rollers of equal diameter which are placed at the fixed distance. It is used for setting and measuring angles together with slip gauges, surface plate and dial test indicator.
  • The name Sine bar, because it works as a hypotenuse in a right angle triangle.

34. Define the specification of a Sine bar?

A sine bar is specified by the distance between the center of two rollers. Sine bars are generally available in 100 mm to 250 mm sizes.

35. What is a Template?

A Template is a model of an object which is designed according to required profile in least expense. It is generally made from mild steel sheet.

36. What are the intentions of using a template?

  • To make identical parts.
  • To check the shape of manufactured parts.

37. What are the favors of a template?

  • Easiest method of marking identical parts.
  • If the design of template is not suitable, it can be repaired or replaced easily.
  • It reduces the production cost.

38. What do you meant by Unilateral and Bilateral system of tolerance?

  • Unilateral Tolerance : If the variation from basic size is in one direction, system of tolerance is called unilateral.
  • Bilateral Tolerance : If the variation from basis size is in both direction, system of tolerance called Bilateral Tolerance.

39. Define Tolerance Zone?

This is the graphical representation of the region between upper and lower limit.

40. What do you meant by Fundamental deviation?

It is the deviation which is conveniently chosen to define the position of the tolerance zone in relation to zero line.

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