Reading a Micrometer - PowerPoint PPT Presentation

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Reading a Micrometer

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The sleeve of the micrometer is a graduated scale with 10 numbered divisions, ... The spindle screw of a micrometer has 40 threads per inch ... – PowerPoint PPT presentation

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Title: Reading a Micrometer


1
Reading a Micrometer
2
Standard Micrometer
Spindle
Anvil
Ratchet Stop
Locknut
Measuring Faces
Sleeve
Thimble
Frame
3
Getting Started
  • Micrometers should always be gripped by the frame
  • Take readings while the instrument is in contact
    with the work piece
  • Use enough pressure on the spindle and anvil to
    obtain a reliable feel

4
Getting Started contd
  • Cylindrical pieces should be checked with
    measurements made 90 degrees apart
  • SAE micrometer readings are stated in thousandths
    (.001) of an inch
  • Always check micrometers for accuracy by zeroing
    them first

5
The Basics
  • The sleeve of the micrometer is a graduated
    scale with 10 numbered divisions, each one being
    1/10 of one inch or .100 apart

6
  • Within these 10 major divisions there are 4 minor
    divisions
  • These 4 minor divisions represent ¼ of .100 or
    .025 (25 thousandths)

7
  • The spindle screw of a micrometer has 40 threads
    per inch
  • One complete revolution moves the spindle 1/40 of
    an inch or .025 (25 thousandths

Spindle Screw
8
  • The thimble has 25 evenly spaced divisions
  • Since one revolution of the spindle equals .025
    then each division on the thimble represents .001

9
What All the Numbers Mean
  • First, count the number of exposed major
    divisions
  • Second, count the number of exposed minor
    divisions
  • Third, take the reading on the thimble

10
For Example
  • 6 major divisions (.600)
  • 1 minor division (.025)
  • Measurement equals .625 which also equals 5/8
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