Metrology and Inspection MCQ Quiz in मल्याळम - Objective Question with Answer for Metrology and Inspection - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

Center line average is given by

\({R_a} = \frac{{\sum a \;+ \;\sum b}}{n }\)

Where ∑a → sum of height in +y direction, ∑b → sum of height in –y direction,

n → number of division

Calculation:

\({R_a} = \frac{{{a_1} + {a_2} + {b_1} + {b_2}}}{4}\)

\({R_a} = \frac{{1 + 1 + 1 + 1}}{4}\)

∴ R_a = 1

Concept:

Interference fit: Interference is the difference between the size of the hole and the size of the shaft which is always negative i.e. shaft is always larger than the hole size. Here the tolerance zone of the hole will be below the tolerance zone of the shaft.

Maximum Interference = Upper limit of the shaft – Lower limit of hole

Calculation:

Given:

Hole \(30_{ + 0.03}^{ + 0.06}\)  mm, Shaft  \(30_{ - 0.02}^{+ 0.04}\) mm

Upper limit of shaft = 30 + 0.04 = 30.04 mm

Lower limit of hole = 30 + 0.03 = 30.03 mm

Maximum Interference = Upper limit of the shaft - Lower limit of hole

A feeler gauge is a tool used to measure gap widths. Feeler gauges are mostly used in engineering to measure the clearance between two parts.

They consist of a number of small lengths of steel of different thicknesses with measurements marked on each piece.

The Go and No -Go principle of gauging is that the Go - end of the gauge must go into the feature of the component being checked and the No - Go end must not go into the same feature.

Explanation: ​

Slip gauges:

• Slip gauges are very precisely manufactured for measuring, setting up of sizes and also to calibrate precision measuring instruments or inspection gauges.
• They can be used to measure tolerances in the range of 0.001 to 0.0005 mm very accurately. With the slip gauges, we can measure a finer tolerance limit.
• Therefore, slip gauges are used for checking the accuracy of the limit gauge.

​

Feeler gauges:

• A feeler gauge is a tool used to measure gap widths.
• Feeler gauges are mostly used in engineering to measure the clearance between two parts like spark plug gaps, bearing clearance, the gap between the mating parts, etc.  
• They consist of a number of small lengths of steel of different thicknesses with measurements marked on each piece.

Ring gauges:

• Ring Gages also referred to as Plain Cylindrical Ring Gauges.
• They are used to check the outside diameter limit on manufactured parts.
• When they are used to check a part directly, the cylindrical ring gages are referred to as GO and NOGO.
• The GO ring gauge checks the upper limit of the part tolerance while the NOGO ring gauge checks the lower limit.

​

​Plug gauge:

• A plug gauge is a cylindrical type of gauge, used to check the accuracy of holes.
• They are used to check the inside diameter limit on manufactured parts.
• The GO plug gauge checks the lower limit of the part tolerance while the NOGO plug gauge checks the upper limit.

​

Explanation:

For tool-room and other precision work, the ordinary methods of measurement are not always accurate. Micrometre and verniers calliper can be used to check tolerance fine within 0.002 to 0.02 mm, but for fine tolerances, they are not effective. With the slip gauges, we can measure a finer tolerance limit.

Slip gauges are very precisely manufactured for measuring, setting up of sizes and also to calibrate precision measuring instruments or inspection gauges. They can be used to measure tolerances in the range of 0.001 to 0.0005 mm very accurately. These are used as the standard unit of length

Therefore, slip gauges are used for checking the accuracy of the limit gauge.

Note:

The accuracy of micrometre and vernier calliper is measured in terms of least count (also known as resolution). The least count of the Vernier calliper ranges from 0.1 mm to 0.02 mm. The least count of the micrometres ranges deeper from 0.01 mm to 0.001 mm.

Line standards: When the length being measured is expressed as the distance between two lines, then it is called “Line Standard”. Example: Measuring scales

End standard: When the length being measured is expressed as the distance between two parallel faces, then it is called “End standards”. Example: Slip gauges, Micrometers

When two light waves interact with each other, the wave effect leads to a phenomenon called interference of light. Instruments designed to measure interference are known as interferometers.

• This interferometer is used for determining actual lengths of slip gauges
• Since the measurement calls for a high degree of accuracy and precision, the instrument should be used under highly controlled physical conditions

​The method of fractional coincidences in interferometric techniques is used for ​the measurement of end gauges.

NPL Flatness Interferometer is used for checking the flatness of the surface.

Plug Gauges are mainly used for measuring hole dimension. The Go-gauge checks the lower limit of a straight hole and the NO-Go gauge checks the upper limit.

Snap Gauges: Used as a quick means for checking sizes within certain limits by comparing the size of the parts with the opening of the gauge.

Feeler Gauge is used to measure gap width or clearance between the mating parts.

Fillet Gauge: It is also known as Radius gauge. Components are machined to have a curved formation on the edges or at the junction of two parts, which are known as a fillet. The gauges used to check the radius of fillet are fillet gauges.

Concept:

Allowance is minimum clearance or maximum interference.

Calculation:

Given:

\(\begin{array}{l} Shaft = \;30_{ - 0.08}^{ - 0.021}mm\;\phi \\ Hole = \;30_{ - 0.000}^{ + 0.023}mm\;\phi \end{array}\)

Since, the maximum size of ths shaft is less than minimum size of the hole so this system is of a clearance fit.

so, Allowances = Minimum clearance

Minimum clearance = Minimum Hole size – Maximum shaft size

= 30.000 – (30 - 0.021)

= 0.021 mm

Jenny calipers have one leg with an adjustable divider point, while the other is a bent leg.

It is also known as Odd leg calipers, Hermaphrodite calipers, leg and point caliper or Odd leg jennys.

These are used for marking lines parallel to the inside and outside edges, for finding the center of round bars.

Detailed Concept and Video Solution

Explanation:

Manufacturing or Engineering tolerance

Manufacturing or Engineering tolerance is the permissible limit or limits of variation in a physical dimension.

Different type of tolerance has been defined for the manufacturing of any component.

This tolerance grade can be shown by a pre define symbol, a list has been shown below.