Measurement
Instruments &Tools
Accurate Measurement
Objectives
What is an ‘accurate’ measurement
 Review different types of measuring
instruments and their application
 Learn how to calibrate instruments
 Care and maintenance of instruments
 Advanced diagnostic session 

Why are these measuring devices
called ‘instruments’
Definition of Accurate
(from dictionary)

free from error especially as the result of
care

able to give an accurate result
What happens if you do not measure accurately?
Examples of
Failed Measurements
YouTube - LS1 Blows Engine
Name here
Measuring Instruments
Micrometers
 Vernier Calipers
 Dial Indicators
 Telescopic Gauges
 Small Hole Gauges
 Thickness Gauges
 Straight Edge

Outside Micrometer
Instrument for making precise linear measurements
of dimensions such as diameters, thicknesses, and
lengths of solid bodies.
It consists of a C-shaped frame with a movable jaw
operated by a screw. The accuracy of the
measurements depends on the accuracy of the
screw-nut combination.
Imperial and Metric
Inside Micrometer
Depth Micrometer
Outside Micrometer
Inside Micrometer
Depth Micrometer
Can you identify the metric micrometer ?
Digital Micrometers
Combination Digital
Metric or Imperial
at the push of a
button
Parts of a Micrometer
Precision Instrument
Micrometer Don’ts
Do not drop
 Do not run over
 Do not over tighten (it is not a vice)
 Do not drop in chemicals
 Do not leave it covered in grease
 Do not let anyone borrow it
 Do not leave lying around

Micrometer Do’s
Keep clean
 Keep calibrated
 Keep in storage box
 Keep locked up
 Keep away from everyone
 Keep in practice reading it !

Using an Outside Micrometer
Using a Depth Micrometer
Using Inside Micrometer
Brake Drum Micrometer
Essentially it is a heavy duty Inside Micrometer
Measuring a brake rotor
What is the name of the micrometer in the picture?
Steps to reading a micrometer
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Calibrate unit
Identify scale (metric or imperial)
Identify range of micrometer (size)
Read Sleeve first number you see
Read Sleeve for second number
(graduation)
Read Thimble
Note-if it is a 4 digit mic, read last number
on Sleeve (will discuss later)
Step # 1 Calibrate Micrometer
Before using any measuring instrument you must
check to ensure it is calibrated (accurate)
TGB Computing & Publishing
YouTube - measuring the thickness of a block using a micrometer
www.tgbcomputing.com
Step # 2 Identify scale
Step # 3 Identify Range (size)
Where to find range
Imperial equivalent would be a 0-1”
Step # 4 Reading the Sleeve and
Example shows 0.341
Thimble
Number on Sleeve
1
3
Number on
Thimble
Imperial Micrometer
2
Graduation on Sleeve
Thimble numbers go from 0 to 20
Sample Reading
Example using a 0-1” Outside Micrometer
First number
is the size of
the Mic
0.000
Second number
is the first
number
on Sleeve
.000
Third number
is .025 graduations
you see on Sleeve
.025 x 2 = .050
Fourth number
is read on the
Thimble
.016
Recording Measurement from Sample
Reading
 First reading – Range of Mic.
0 – 1” so the first number would be 0.000
 Second reading – number on Sleeve
Number you see is Zero so it would be .000
 Third reading – graduation on Sleeve
Two graduations exposed so number is .050
 Final number is number on the Thimble
Final number is .016
Total Readings
First reading – Range of Mic.
0.000
 Second reading – number on Sleeve
0.000
 Third reading – graduation on Sleeve
0.050
 Final number is number on the Thimble 0.016
______
Total is ?
0.066
Reading an Imperial Micrometer
Reading an Imperial Micrometer
Exercise # 1
(2-3” mic)
Answer : 2.550
Reading an Imperial Micrometer
Exercise # 2
(0-1” mic)
Answer:
0.802
Reading an Imperial Micrometer
Exercise # 3
(1-2” mic)
Answer:
1.645
Reading a Metric Micrometer
Reading a Metric Micrometer
Notice that Thimble numbers are higher than the
Imperial Mic ? That’s how you know it is Metric scale.
Thimble numbers go from 0 to 45
Example of 4 digit Metric Micrometer 0.0000
Reading a Metric Micrometer
Exercise # 1 (0-25mm Range)
Answer : 12. 69
Reading a Metric Micrometer
Exercise # 2 (0-25mm Range)
Answer : 23.99
Telescopic Gauges
Spring loaded
Measure large inside dia.
Using Telescopic Gauges
Small Holes Gauges
Measure small
Inside Diameters
Dividers or Caliper
Instrument that consists of two
adjustable legs or jaws for
measuring the dimensions of
material parts.
Outside calipers measure
thicknesses and outside diameters
of objects; inside calipers
measure hole diameters and
distances between surfaces.
Standard Vernier Caliper
Instrument for making very accurate linear or angular
measurements.
Introduced in 1631 by Pierre Vernier (c. 1580–1637), it uses
two graduated scales: a main scale similar to that on a ruler,
and a specially graduated scale, the vernier, that slides
parallel to the main scale and enables readings to be made to
a fraction of a division on the main scale.
Why buy a Vernier Caliper?
 Durable
 Accurate measuring instrument
 Multiple reading use
 Easy to store and maintain
Readings that can be taken
 Outside Diameter
 Inside Diameter
 Thickness
 Depth
Can this instrument not take place of a mic?
Dividers or Caliper
Small Holes Gauges
Telescopic Gauges
Dial Vernier Caliper
Digital Vernier Caliper
YouTube - Digital Caliper Bug
Using a Vernier Caliper
How to use and read a Vernier Caliper
YouTube - all about verniers
Checking calibration of Vernier Caliper and allowing
for error
YouTube - measuring a weight using a vernier caliper
Reading a Vernier Caliper # 1
2.641
Reading a Vernier Caliper # 2
1.581
Reading a Vernier Caliper # 2
0.508
Dial Indicators
Any of a number of
deviation-type gauges that
indicate the amount by which
an object being gauged
deviates from the standard.
This deviation is shown in
units of measurement, in
which movement of a
gauging spindle deflects a
pointer on a graduated dial
Calibration of Dial Indicator
Turn dial until pointer
aligns with the Zero
TGB Computing & Publishing
Note-example of
Metric Dial Indicator
Calibration button
Dial Indicator with Stand
Very useful instrument for checking Steering
and Suspension components
Simpler Measuring Devices
Thickness Gauges
Flat Blade Feeler Gauges
 Wire Gauges
 Taper Gauge

Metric Feeler Gauges
Imperial Feeler Gauges
Straight Edge
Accurately machined surface
References - Links
YouTube - all about verniers
YouTube - measuring a weight using a
vernier caliper
YouTube - measuring the thickness of a
block using a micrometer
www.tgbcomputing.com
TGB Computing & Publishing