Transcript Measuring Tools

Measuring Tools
Introduction
Measuring tools for small engines are divided into three categories.
– Direct reading
– Measurement transferring
– Reject gages
Direct Reading Measuring Tools
Small engines use two types of direct reading measuring tools:
1. Micrometers
2. Calipers
Micrometers
Micrometer Introduction
•
•
•
•
A micrometer is a mechanical device
designed to measure distances as small
as 1/10,000 of an inch (0.0001 in).
Micrometers are only one (1) inch long.
The micrometer is used with different
types and sizes of frames to provide
precise measurements of many different
objects.
Small engines uses three (3) types of
micrometers:
1. Micrometer caliper
2. Inside micrometer
3. Depth gauge micrometer
Micrometer calipers are available in
mechanical and digital models.
Micrometer Caliper
• A micrometer caliper uses a frame that allows the
micrometer to measure the thickness of objects.
• For small engine use, different frame sizes are used to
provide a wider measurement range.
– One inch
– Two inch
– Etc.
Reading Micrometer Caliper-parts
• The first step in being able to read a micrometer is learning the
names of the parts.
 The face of the anvil and the
face of the spindle are the
contact surfaces.
 The spindle and thimble turn
together.
 The ratchet/friction stop
improves the repeatability of
measurements for beginners.
 A micrometer caliper is read
at the point were the edge of
the thimble crosses the barrel
scale
•
Insure the lock is released before trying to turn the thimble..
Reading Micrometer Caliper-barrel
• A micrometer caliper is read
just like an ruler.
• Start by determining the
smallest whole unit, and then
determine the values of each
sub division.
• The smallest whole unit is
determined by the frame size. • The micrometer barrel scale is
– One (1) inch frame = 0.0
one (1) inch long and is
smallest whole unit
divided into ten (10) sections.
– Two (2) inch frame = 1.0
• Each number on the barrel
smallest whole unit.
scale = 1/10 or 0.1 inch.
– Etc.
Reading Micrometer Caliper-barrel
• Each 1/10 of an inch on
the barrel scale is divided
into 4 segments.
1
1
1
 4 =
x
10
10
4
1
=
 0.025
40
• Each short line = 0.25 inches (25
thousands of an inch).
Reading Micrometer Caliper-thimble
• The last step is reading the value on the thimble scale.
• The thimble scale subdivides the last segment on the barrel
scale.
• The smallest segment on the barrel
is 25 thousands (0.025).
• The thimble is divided into 25
segments = 1/1,000 or 0.001 inch.
Micrometer Caliper Example
• Determine the reading for the micrometer caliper in the illustration.
1.
2.
3.
4.
Smallest whole unit
Tenths of an inch
Twenty five thousands ( 0.025 x 2 )
Thousands
Sum (measurement)
0.000
0.300
0.050
0.015
0.365
Micrometer Caliper-digital
• Most measuring tools
are available with a
digital readout.
• Advantages
– Easier to read.
– Can be interfaced with
data collection devices
for automatic recording.
– Easy to convert between
English and metric units.
• Disadvantages
– Requires battery
– More expensive
Inside Micrometer
• Inside micrometers have
been replaced by dial
calipers and other tools for
small gas engines.
• The principles for reading
are the same.
• The primary difference is
determining the smallest
whole unit.
• The physical size of the micrometer limits the
smallest whole unit to 1 or 1-1/2 inch.
• Extensions are added to set the minimum size
to the desired range.
Inside Micrometer Example
Read the inside micrometer in the illustration.
Smallest whole unit
Tenths
Twenty Five Thousands
Thimble
Sum (reading)
1.500
0.200
0.025
0.014
1.734
Inside Micrometer Example 2
• Inside micrometers use extensions to change the range of
measurements.
• Adding an extension increases the minimum measurement.
In this example a 1/2 inch
extension has been added.
Smallest whole unit
Tenths
Twenty five thousands
Thousands
Reading
2.000
0.200
0.075
0.001
2.276
Note: when the zero on the thimble is close to the reference line and a 25
thousands line is close to the edge of the thimble, it may be difficult to
determine if the last line that should be counted. If the thimble zero is above
the reference line the line is not counted. If it is below it should be counted.
Depth Gauge Micrometer
Thimble
Spindle
• Depth gauge micrometers are
used to measure the depth of
blind holes, slots, key ways,
etc.
• The spindle length can be
changed to set the
micrometer for the desired
range of measurement.
• To read a depth gauge
micrometer you must
visualize the distance that
has been covered by the
thimble.
Depth Gauge Micrometer Example
Read the depth gauge micrometer in
the illustration
Smallest whole unit
Tenths
Twenty Five Thousands
Thousands
Sum (reading)
0.000
0.800
0.050
0.017
0.867
Calipers
Introduction
• Calipers can be direct reading or measuring transferring tools.
• Direct reading calipers are capable of a wider measurement
range than micrometer calipers.
– Six (6), eighteen (18) and twenty four (24) inch are popular.
• Three common designs of direct reading calipers;
– Vernier
– Dial
– Digital
Vernier Caliper
• Vernier calipers are an old tool that has been mostly replaced
by dial and digital calipers.
• They are manufactured with decimal scales, metric scales and
fractional scales.
• The Vernier scale is still used on many mechanical measuring
tools.
Vernier Scale
•
A Vernier is a
mechanical means of
magnifying the last
segment on the main
scale so addition
subdivisions can be
made.
• The reference point is the 0 on the vernier scale.
• To read a Vernier, the line of coincidence must be located.
• The line of coincidence (LOC) is the line on the Vernier that
coincides with a line on the main scale.
– Illustration LOC = 19
• In theory only one LOC is possible, but usually when reading the
vernier it appears several exist. When this occurs pick the
middle line.
Vernier Caliper-practice
Read the Vernier caliper in the illustration.
LOC
•
•
•
•
Smallest whole unit
Tenths of an inch
Twenty five thousands
Vernier scale
Sum (measurement)
1.000
0.200
0.000
0.011
1.211
Dial Caliper
A dial replaces the Vernier.
This makes the caliper easier to read.
The reader must still determine the units and graduations.
Measurement Transferring Tools
Introduction
• Measurement transferring tools are tools that collect a
measurement, but do not have a scale to read the
measurement.
• Common tools are:
–
–
–
–
Spring calipers
Dividers
Telescoping gauges
Ball gauges
Spring Calipers
• Spring calipers are used to transfer
measurements.
• Three types of spring calipers
– Outside
– Inside
– Hermaphrodite
Dividers
• Dividers are very useful for laying
out several equal distances or
transferring a distance
measurement when other
measuring devices cannot be
used.
Telescoping gages
• Telescoping gages are used to
measure inside diameters.
• One or both ends are spring
loaded so they can be retracted
and inserted into the hole being
measured.
• The measurement is made with
a caliper or micrometer.
Ball Gauges
• Ball gauges are use to transfer
measurements that are too small for
telescoping gauges.
• The ball is split and a tapered wedge is
used to increase and decrease the
diameter of the ball halves.
The End