An automotive technician measures the thickness of a solid brake rotor using a standard 0 … — Armed Services Vocational Aptitude Battery (ASVAB)

An automotive technician measures the thickness of a solid brake rotor using a standard 0 to 1-inch outside micrometer. On the sleeve, the major number 8 is visible along with 2 full subdivision marks past it. The thimble line aligned with the sleeve datum index is 17. What is the measured thickness of the brake rotor?

A
$0.842\text{ in}$
$0.867\text{ in}$ Answer
C
$0.817\text{ in}$
D
$0.892\text{ in}$

Answer

0.867\text{ in}

On a standard inch micrometer, the sleeve scale has numbered divisions representing

0.100\text{ in}

each and small subdivision marks representing

0.025\text{ in}

each. The thimble divides each revolution into 25 equal increments of

0.001\text{ in}

. Adding the major sleeve reading (

0.800\text{ in}

), the two subdivision marks (

2 \times 0.025 = 0.050\text{ in}

), and the thimble reading (

0.017\text{ in}

) yields

0.867\text{ in}

Step-by-Step Solution

Read the major graduation on the micrometer sleeve

Major reading =

0.800\text{ in}

Each numbered mark on a standard inch micrometer sleeve represents one-tenth of an inch (

0.100\text{ in}

), so 8 represents

0.800\text{ in}

Count the visible subdivision lines on the sleeve past the major mark

Subdivision reading =

2 \times 0.025\text{ in} = 0.050\text{ in}

Each small subdivision line on the sleeve represents one revolution of the thimble, or

0.025\text{ in}

Read the thimble graduation aligned with the sleeve datum line

Thimble reading =

0.017\text{ in}

Each division on the thimble represents one-thousandth of an inch (

0.001\text{ in}

Sum all three readings to determine total thickness

0.800\text{ in} + 0.050\text{ in} + 0.017\text{ in} = 0.867\text{ in}

The total micrometer measurement is the sum of the major sleeve mark, minor sleeve subdivisions, and aligned thimble value.

Key Concept

Reading a Standard Inch Outside Micrometer

Estimated Time:1m 0s

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