Use of four ball method in measurement - Metrology & Quality Control

Q.  Which among the following is measured using four ball method?
- Published on 07 Aug 15

a. Diameter
b. Length
c. Angle
d. All of the above

ANSWER: Diameter

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    Discussion

  • Sravanthi   -Posted on 13 Oct 15
    Four ball method is used to measure diameter of bore. In this method, three balls of equal diameter are evenly placed in the bore and a fourth ball of same or different diameter is placed above them. Diameter of the bore can be measured by knowing the height and diameter of the balls.

    Therefore bore diameter is measured is calculated by using the formula shown below,

    D = 2 √ (2 Hd – H2) + d

    here,
    D = bore diameter
    d = diameter of balls
    H = height of balls placed

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