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Figure 3-1 Common types of rules.
CHAPTER 3
MEASURING TOOLS AND TECHNIQUES
As an Aviation Boatswains Mate, Launch and Recovery Equipment
(ABE), you will be performing maintenance and repair tasks on
catapults and arresting gear equipment, so you must take accurate
measurements during inspection, to determine the amount of wear or
service life remaining on a particular item or to make sure
replacement parts used to repair equipment meet established
specifications. The accuracy of these measurements, often affecting
the performance and failure rates of the concerned equipment,
depends on the measuring tool you use and your ability to use it
correctly.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the
following:
1. List the different types of measuring tools.
2. Describe the uses of different types of measuring tools.
3. Describe the proper care of measuring tools.
COMMON MEASURING TOOLS
You will use many different types of measuring tools in the
daily performance of your duties. Where exact measurements are
required, use a micrometer caliper (mike). If you use the
micrometer caliper properly, it will allow you to measure within
one ten-thousandth (0.0001) of an inch accuracy. On the other hand,
where accuracy is not extremely critical, a common straightedge
rule or tape rule will suffice for most measurements.
Rules and Tapes
Figure 3-1 illustrates some of the commonly used straightedge
and tape rules. Of all measuring tools, the simplest and most
common is the steel or wooden straightedge rule. This rule is
usually 6 or 12 inches long, although other lengths are available.
Steel rules may be flexible or nonflexible, but the thinner the
rule is, the easier it is to measure accurately with it, because
the division marks are closer to the work to be measured.
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Figure 3-2 Measuring and reading with a rule.
Figure 3-3 Measuring the length of a bolt or screw.
Generally, a rule has four sets of graduated division marks, one
on each edge of each side of the rule. The longest lines represent
the inch marks. On one edge, each inch is divided into 8 equal
spaces, so each space represents 1/8 inch. The other edge of this
side is divided into sixteenths. The 1/4 inch and 1/2 inch marks
are commonly made longer than the smaller division marks to
facilitate counting, but the graduations are not normally numbered
individually, as they are sufficiently far apart to be counted
without difficulty. The opposite side of the rule is similarly
divided into 32 and 64 spaces per inch, and it is common practice
to number every fourth division for easier reading.
There are many variations of the common rule. Sometimes the
graduations are on one side only, sometimes a set of graduations is
added across one end for measuring in narrow spaces, and sometimes
only the first inch is divided into 64ths, with the remaining
inches divided into 32nds and 16ths. Steel tapes are made from 6 to
about 300 feet in length. The shorter lengths are frequently made
with a curved cross section so that they are flexible enough to
roll up, but remain rigid when extended. Long, flat tapes require
support over their full length when measuring, or the natural sag
will cause an error in reading.
Measuring Procedures
To take a measurement with a common rule, hold the rule with its
edge on the surface of the object being measured. This will
eliminate parallax and other errors that might result because of
the thickness of the rule. Read the measurement at the graduation
that coincides with the distance to be measured, and state it as
being so many inches and fractions of an inch (Figure 3-2). Always
reduce fractions to their lowest terms; for example, 6/8 inch would
be called 3/4 inch. A hook or eye at the end of a tape or rule is
normally part of the first measured inch.
Bolts and screws are best measured by holding them up against a
rigid rule or tape. Hold both the rule and the bolt or screw to be
measured up to your eye level, so that your line of sight will not
create error in reading the measurement. As shown in Figure 3-3,
the bolts or screws with countersink-type heads are measured from
the top of the head to the opposite end, while those with other
types of heads are measured from the bottom of the head.
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Figure 3-4 Measuring the outside diameter of a pipe.
Figure 3-5 Measuring the inside diameter of a pipe.
Outside Pipe Diameters
To measure the outside diameter of a . As shown in Figure 3-4,
line up the end of the rule with one side of the pipe, using your
thumb as a stop. Then, with the one end held in place with your
thumb, swing the rule through an arc and take the maximum reading
at the other side of the pipe. For most purposes, the measurement
obtained by using this method is satisfactory. It is necessary that
you know how to take this measurement, as the outside diameter of
pipe is sometimes the only dimension given on pipe
specifications.
Inside Pipe Diameters
To measure the inside diameter of a pipe with a rule, as shown
in Figure 3-5, hold the rule so that one corner of the rule just
rests on the inside of one side of the pipe. Then, with one end
thus held in place, swing the rule through an arc and read the
diameter across the maximum inside distance. This method is
satisfactory for an approximate inside measurement.
Pipe Circumferences
To measure the circumference of a pipe, you must use a
flexible-type rule that will conform to the shape of the pipe. A
fabric or steel flexible tape rule is adaptable to this job. When
measuring the pipe, make sure the tape is wrapped squarely around
the axis of the pipe to ensure that the measurement will not be
more than the actual circumference of the pipe. This is extremely
important when you are measuring a large diameter pipe.
NOTE
Common tapes and rules usually are not graduated in units
smaller than sixteenths. Measuring in fractions smaller than
sixteenths requires precision measuring tool such as
micrometer.
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Figure 3-6 Measuring the
circumference of a pipe with a tape.
Figure 3-8 Measuring an inside dimension with a tape rule.
Hold the rule or tape as shown in Figure 3-6. Take the reading,
using the 2-inch graduation, for example, as the reference point.
Then subtract the reference from the total reading. In this case
the correct reading is found by subtracting 2 inches from the
actual reading. In this way the first 2 inches of the tape, serving
as a handle, will enable you to hold the tape securely.
Inside Dimensions
For an inside measurement such as the inside of a box, a folding
rule that incorporates a 6- or 7-inch sliding extension is one of
the best measuring tools. To take the inside measurement, first
unfold the folding rule to the approximate dimension. Then, extend
the end of the rule and read the length that it extends, adding the
length of the extension to the length on the main body of the
rule.
In Figure 3-7, the length of the main body of the rule is 13
inches, and the extension is pulled out 3 3/16 inches; the total
inside dimension being measured is 16 3/16 inches.
Notice in the circled inset in Figure 3-8 that the hook at the
end of the particular rule shown is attached to the rule so that it
is free to move slightly.
When an outside dimension is taken by hooking the end of the
rule over an edge, the hook will move to locate the end of the
rule even with the edge of the surface from which the
measurement is being taken. By being free to move, the hook will
retract toward the end of the rule when an inside dimension is
taken.
To measure an inside dimension using a tape rule, extend the
rule between the surfaces as shown in Figure 3-8, take a reading at
the point on the scale where the rule enters the case, and add 2
inches. The 2 inches are the length of the case. The total is the
inside dimension being taken.
Figure 3-7 Using a folding rule to measure inside dimension.
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Outside Dimensions
To measure an outside dimension using a tape rule, hook the rule
over the edge of the stock. Pull the tape out until it projects far
enough from the case to permit measuring the required distance. The
hook at the end of the rule is designed so that it will locate the
end of the rule at the surface from which the measurement is being
taken. When taking a measurement of length, hold the tape parallel
to the lengthwise edge. For measuring widths, the tape should be at
right angles to the lengthwise edge. Read the dimension of the rule
exactly at the edge of the piece being measured. It may not always
be possible to hook the end of the tape over the edge of stock
being measured. In this case it may be necessary to butt the end of
the tape against another surface or to hold the rule at a starting
point from which a measurement is to be taken.
Distance Measurements
Steel or fiberglass tapes are generally used for making long
measurements. Secure the hook end of the tape. Hold the tape reel
in the hand and allow it to unwind while walking in the direction
in which the measurement is to be taken. Stretch the tape with
sufficient tension to overcome sagging. At the same time, make sure
the tape remains parallel to the edge or the surface being
measured.
Care of Rules and Tapes
Handle rules and tapes carefully and keep metal ones lightly
oiled to prevent rust. Never allow the edges of measuring devices
to become nicked by striking them with hard objects. They should
preferably be kept in a wooden box when not in use. To avoid
kinking tapes, pull them straight out from their casesdo not bend
them backward. With the windup type, always retract the tape in
clockwise directionturning it backward will kink or break the tape.
With the spring-wind type, guide the tape by hand. If it is allowed
to snap back, it may be kinked, twisted, or otherwise damaged. Do
not use the hook as a stop. Slow down as you reach full
extension.
SIMPLE CALIPERS
Simple calipers are used in conjunction with a scale or rule to
determine the thickness or the diameter of a surface, or the
distance between surfaces. A caliper is usually used in one of two
ways. Either the caliper is set to the dimension of the work and
the dimension transferred to a scale, or the caliper is set on a
scale and the work machined until it checks with the dimension set
up on the caliper.
To adjust a caliper to a scale dimension, hold one leg of the
caliper firmly against one end of the scale and adjust the other
leg to the desired dimension. To adjust a caliper to the work, open
the legs wider than the work and then bring them down to the work.
The calipers you will most commonly use are shown in Figure
3-9.
Outside calipers for measuring outside diameters are bow-legged;
those used for inside diameters have straight legs with the feet
turned outward. Calipers are adjusted by pulling or pushing the
legs to open or close them. Fine adjustment is made by tapping one
leg lightly on a hard surface to close them, or by turning them
upside down and tapping on the joint end to open them.
Spring-joint calipers have the legs joined by a strong spring
hinge and linked together by a screw and adjusting nut. For
measuring chamfered cavities (grooves) or for use over flanges,
transfer calipers are available. They are equipped with a small
auxiliary leaf attached to one of the legs by a screw (Figure 3-9).
The measurement is made as with ordinary calipers; then the leaf is
locked to the leg. The legs may then be opened or closed as needed
to clear the obstruction, and brought back and locked to the leaf
again, thus restoring them to the original setting.
Another type of caliper is the hermaphrodite, sometimes called
the odd-leg caliper. This caliper has one straight leg ending in a
sharp point, sometimes removable, and one bowleg. The hermaphrodite
caliper is used chiefly for locating the center of a shaft, or for
locating a shoulder.
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Figure 3-9 Simple non-calibrated calipers.
CAUTION
Never place a caliper on work that is revolving in a
machine.
NOTE
Keep calipers clean and dry. Protect the points against damage.
Store calipers where they will not become bent or
broken.
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Figure 3-10 Using outside caliper.
Figure 3-11 Measuring the distance between two surfaces with an
inside caliper.
Measuring Diameter of a Pipe or Thickness of Flat Object
To measure the diameter of a pipe or the thickness of flat
object, adjust the outside caliper so that you feel a slight drag
as you pass it over the pipe object as shown in Figure 3-10. After
the proper "feel" has been attained, measure the setting of the
caliper with a rule. In reading the measurement, sight over the leg
of the caliper after making sure the caliper is set squarely with
the face of the rule.
Measuring Distance between Two Surfaces
To measure the distance between two surfaces with an inside
caliper, first set the caliper to the approximate distance being
measured. Hold the caliper with one leg in contact with one of the
surfaces being measured (Figure 3-11). Then, as you increase the
setting of the caliper, move the other leg from left to right. Feel
for the slight drag indicating the proper setting of the caliper.
Then, remove the caliper and measure the setting with a rule.
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Figure 3-13 Measuring hard-to-reach inside dimension.
Measuring Hard-to-Reach Dimensions
To measure an almost inaccessible outside dimension, such as the
thickness of the bottom of a cup, use an outside transfer
firm-joint caliper as shown in Figure 3-12.
When the proper "feel" is obtained, tighten the lock joint.
Then, loosen the binding nut and open the caliper enough to remove
it from the cup. Close the caliper again and tighten the binding
nut to seat in the slot at the end of the auxiliary arm. The
caliper is now at the original setting, representing the thickness
of the bottom of the cup. The caliper setting can now be measured
with a rule.
To measure a hard-to-reach inside dimension, such as the
internal groove shown in Figure 3-13, use an inside transfer
firm-joint caliper. Use the same procedure as for measuring a
hard-to-reach outside dimension.
Figure 3-12 Measuring the thickness of the bottom of a cup.
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Figure 3-14 Measuring an inside diameter
using inside caliper.
Figure 3-15 Setting a combination firm-joint caliper.
Measuring Hole Diameters
To measure the diameter of a hole with an inside caliper, hold
the caliper with one leg in contact with one side of the hole
(Figure 3-14) and, as you increase the setting, move the other leg
from left to right, and in and out of the hole. When you have found
the point of largest diameter, remove the caliper and measure the
caliper setting with a rule.
Setting a Combination Firm-Joint Caliper
To set a combination firm-joint caliper with a rule, when the
legs are in position for outside measurements, grasp the caliper
with both hands as shown in Figure 3-15, view A and adjust both
legs to the approximate setting. After you adjust both legs, the
shape of the tool will be approximately symmetrical. Thus, it will
maintain its balance and be easier to handle. Check this
approximate setting as shown in Figure 3-15, view B. Sight squarely
across the leg at the graduations on the rule to get the exact
setting required.
If it is necessary to decrease or increase the setting, tap one
leg of the caliper as shown in Figure 3-16. The arrow indicates the
change in setting that will take place. When the caliper is set for
inside measurements, the same directions for adjusting the setting
apply.
Figure 3-16 Decreasing and increasing the setting of a
firm-joint caliper.
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Figure 3-17 Setting a combination firm-
joint caliper for inside measurement.
Figure 3-17 shows how the end of the rule and one leg of the
caliper are rested on the bench top so that they are exactly even
with each other when the reading is taken.
Setting Outside and Inside Spring Calipers
To set an outside spring caliper to a particular reading, first
open the caliper to the approximate setting. Then, as shown in
Figure 3-18, place one leg over the end of the rule, steadying it
with the index finger. Make the final setting by sighting over the
other leg of the caliper squarely with the face of the rule at the
reading, and turning the knurled adjusting nut until the desired
setting is obtained.
NOTE
Keep calipers clean and dry. Make sure they are always stored in
a case or box when not in use to protect from
damage.
Figure 3-18 Setting an outside spring caliper.
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Figure 3-19 Setting an inside spring
caliper.
Figure 3-20 Transferring measurements from caliper to
caliper.
Figure 3-21 Thickness (feeler) gage.
To set an inside spring caliper to a particular reading, place
both caliper and rule on a flat surface as shown in Figure 3-19.
The rule must be held squarely or perpendicular (90E in both
directions) to the surface to ensure accuracy. Adjust the knurled
adjusting nut, reading the setting on the rule with line-of-sight
normal to the face of the rule at the reading.
Transferring Measurements from One Caliper to Another
To transfer a measurement from one spring caliper to another,
hold the calipers as shown in Figure 3-20. Note that one of the
man's fingers is extended to steady the point of contact of the two
lower caliper legs. In this figure the inside caliper is being
adjusted to the size of the outside caliper. As careful
measurements with calipers depend on one's sense of touch, which is
spoken of as "feel," calipers are best held lightly. When you
notice a slight drag, the caliper is at the proper setting.
Thickness (Feeler) Gages
Thickness (feeler) gages, as shown in Figure 3-21, are made in
many shapes and sizes; usually 2 to 26 blades are grouped into one
tool and graduated in thousandths of an inch.
Most thickness blades are straight, while some are bent at the
end at 45 degree and 90 degree angles. Some thickness gages are
grouped so that there are several short and several long blades
together. Thickness gages are also available in single blades and
in strip form for specific measurements. For convenience, many
groups of thickness gages are equipped with a locking screw in the
case that locks the blade to be used in the extended position.
These gages are fixed in leaf form, which permits the checking and
measuring of small openings such as contact points, narrow slots,
and so forth. They are widely used to check the flatness of parts
in straightening and grinding operations and in squaring objects
with a try square.
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Figure 3-22 Common types of micrometer.
MICROMETER CALIPERS
More widely used by ABEs than even common calipers are the
various types of micrometer calipers. Micrometer calipers are
precision measuring equipment (PME) and, as was stated earlier, you
can use micrometer calipers to take accurate measurements to the
nearest one ten-thousandth of an inch. However, in most
applications a measurement to the nearest one thousandth of an inch
is considered acceptable accuracy. These measurements are expressed
or written as a decimal (0.0001, 0.001, 0.01), so to use them you
must know how to read and write decimals.
Types of Micrometers
There are four types of micrometer calipers, commonly called
micrometers or simply mikes, used throughout the Navy: the outside
micrometer, the screw thread micrometer, the inside micrometer, and
the depth micrometer. (Figure 3-22).
The outside micrometer is used for measuring outside dimensions,
such as the outside diameter of a piece of round stock or the
thickness of a piece of flat stock. The screw thread micrometer is
used to determine the pitch diameter of screws. The inside
micrometer is used to measure the inside diameter of a cylinder or
hole. The depth micrometer is used for measuring the depth of a
hole or recess.
Reading a Micrometer
Occasionally you attain a reading in which the horizontal
reference line of the sleeve scale falls between two graduations on
the thimble scale, as shown in Figure 3-23. Paying close attention
to the thimble scale, you can see the horizontal reference line is
closer to the 15 mark than to the 14 mark.
To read this measurement to THREE decimal places, simply round
off to the 15 mark, as shown in example A of Figure 3-23.
To read this measurement to FOUR decimal places, estimate the
number of tenths of the distance between thimble scale graduations
the horizontal reference line has fallen.
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Figure 3-23 Reading sleeve and thimble scales of a
micrometer.
Each tenth of this distance equals one ten-thousandth (0.0001)
of an inch. Add the ten-thousandths to the reading as shown in
example B of Figure 3-23.
NOTE
Precision Measuring Equipment (PME) such as the micrometer is
regularly calibrated for accuracy. Be sure a
micrometer has been calibrated before use.
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Figure 3-24 Nomenclature of an outside micrometer caliper.
Outside Micrometer
The nomenclature of an outside micrometer is illustrated in
Figure 3-24.
The sleeve and thimble scales of a micrometer (Figure 3-25) have
been enlarged and laid out for demonstration. To understand these
scales, you need to know that the threaded section on the spindle,
which revolves, has 40 threads per inch. Therefore, every time the
thimble completes a revolution, the spindle advances or recedes
1/40 inch, or 0.025 inch.
Note the horizontal line on the sleeve is divided into 40 equal
parts per inch. Every fourth graduation is numbered 1, 2, 3, 4, and
so on, representing 0.100 inch, 0.200 inch, 0.300 inch, and 0.400
inch, respectively. When you turn the thimble so its edge is over
the first sleeve line past the 0 on the thimble scale, the spindle
has opened 0.025 inch. If you turn the spindle to the second mark,
it has moved 0.025 inch plus 0.025 inch, or 0.050 inch. When the
beveled edge of the thimble stops between graduated lines on the
sleeve scale, you must use the thimble scale to complete your
reading. The thimble scale is divided into 25 equal parts; each
part or mark represents 1/25th of a turn; 1/25th of 0.025 inch
equals 0.001 inch.
Note that in Figure 3-24 every fifth line on the thimble scale
is marked 5, 10, 15, and so on. The thimble scale permits you to
take very accurate readings to the thousandths of an inch.
NOTE
Keep the sleeve and thimble free of grease and dirt. They cause
inaccurate readings on micrometers.
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Figure 3-25 Sleeve and thimble scales of a micrometer.
CAUTION
Do not drop micrometers. If a micrometer is dropped or bumped,
its accuracy will be affected.
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Figure 3-26 Enlarged micrometer scale.
Figure 3-27 Vernier scale of a micrometer.
The enlarged scale in Figure 3-26 can help you understand how to
take a complete micrometer reading to the nearest thousandth of an
inch.
The thimble is turned far enough to expose the 7 on the sleeve
scale but not far enough to expose the first mark after the 7.
Therefore, the measurement must be between 0.700 inch and 0.725
inch. Exactly how far between 0.700 inch and 0.725 inch must be
determined from the thimble scale.
As you can see, the thimble has been turned through 12 spaces of
its scale, and the 12th graduation is lined up with the reference
line on the sleeve. When the value on the sleeve scale is added to
the value on the thimble scale that is lined up with the reference
line on the sleeve scale, the space between the anvil and spindle
must be 0.712 inch (seven hundred twelve thousandths of an
inch).
Reading the Vernier Scale on an Outside Micrometer
Many times you are required to work to exceptionally precise
dimensions. Under these conditions it is better to use a micrometer
that is accurate to ten-thousandths of an inch. This degree of
accuracy is obtained by the addition of a vernier scale.
The vernier scale of a micrometer (Figure 3-27) furnishes the
fine readings between the lines on the thimble rather than
requiring you to estimate the reading. The 10 spaces on the vernier
are equivalent to 9 spaces on the thimble. Therefore, each unit on
the vernier scale is equal to 0.0009 inch, and the difference
between the sizes of the units on each scale is 0.0001 inch.
When a line on the thimble scale does not coincide with the
horizontal reference line on the sleeve, you can determine the
additional spaces beyond the readable thimble mark by finding which
vernier
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Figure 3-28 Reading a vernier scale.
Figure 3-29 Inside micrometer set.
mark matches up with a line on the thimble scale. Add this
number, as that many ten-thousandths of an inch, to the original
reading.
In Figure 3-28, see how the second line on the vernier scale
matches up with a line on the thimble scale. This means that the
0.011 mark on the thimble scale has been advanced an additional
0.0002 beyond the horizontal sleeve line. When you add this to the
other readings, the reading is 0.200 + 0.075 + 0.011 + 0.0002, or
0.2862, as shown.
Inside Micrometer
The inside micrometer, as the name implies, is used for
measuring inside dimensions, such as pump casing wearing rings,
cylinder,
bearing, and bushing wear.
Inside micrometers usually come in a set that includes a
micrometer head, various length spindles (or extension rods) that
are interchangeable, and a spacing collar that is 0.500 inch in
length. The spindles (or extension rods) usually graduate in ranges
with 1-inch increments; for example, 1 to 2 inches, or 2 to 3
inches (Figure 3-29).
The 0.500 spacing piece is used between the spindle and the
micrometer head so the range of the micrometer can be extended. A
knurled extension handle is usually furnished for obtaining
measurements in hard-to-reach locations.
Reading an Inside Micrometer
To read the inside micrometer, read the micrometer head exactly
as you would an outside micrometer, then add the micrometer reading
to the rod length (including spacing collar, when installed) to
obtain the total measurement.
NOTE
Keep micrometers clean and lightly oiled. Make sure they are
always stored in a case or box when not in use to
protect from damage.
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Figure 3-31 Depth micrometer sleeve and thimble scales.
Figure 3-32 Close-up view of a micrometer.
Depth Micrometer
The depth micrometer is used to measure the precise depths of
holes, grooves, and recesses by using interchangeable rods to
accommodate different depth measurements.
When using a depth micrometer, you must make sure the base of
the micrometer has a flat, smooth surface to rest on and that it is
held firmly in place to ensure an accurate measurement (Figure
3-30).
Reading a Depth Micrometer
When reading a depth micrometer, you will notice that the
graduations on the sleeve are numbered in the opposite direction of
those on an outside or inside micrometer. When you are reading a
depth micrometer, the distance to be measured is the value that is
covered by the thimble. See Figure 3-31; consider the reading
shown.
The thimble edge is between the numbers 4 and 5. This shows a
value of at least 0.400 inch on the sleeve's major divisions. The
thimble also covers the first minor division on the sleeve; this
has a value of 0.025 inch. The value shown on the thimble
circumference scale is 0.010 inch. Adding these three values
together results in a total of 0.435 inch, or the total distance
that the end of the extension rod has traveled from the base. This
measurement added to the length of the extension rod used
gives you the total depth of the hole, recess, or groove that
was measured. Figure 3-32 shows a close-up view of a
micrometer.
Selecting the Proper Micrometer
The types of micrometers commonly used are made so that the
longest movement that the micrometer spindle or rod can make is 1
inch. This movement is called the range; for example, a 2-inch
micrometer has a range of from 1 inch to 2 inches, and can only
measure work with a thickness or diameter within that range.
Therefore, it is necessary to first determine the approximate size,
to the nearest inch, of the work to be measured and then select the
proper size micrometer. The size of a micrometer indicates the size
of the largest work it can measure.
Figure 3-30 Using a depth micrometer.
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Figure 3-33 Choke ring gage set.
Other Special Measuring Tools
The measuring tools that have been described in this chapter are
the ones that you, as an ABE, will routinely use while performing
your assigned duties. You may, however, occasionally be required to
use other less commonly used measuring tools. Some of these are the
dial indicator, telescopic gage, ring gages, snap gages, gage
block, sliding T-bevel, protractor, wire gages, and screw thread
gage. The description of these tools and instructions for their use
can be found in the training manual Use and Care of Hand Tools and
Measuring Tools, Navy Education Training Manual (NAVEDTRA)
12085.
CHOKE RING GAGE SET
The choke ring gage set (Figure 3-33) and its associated
components make up a portable electronic mechanical bore gage
designed to be used by ABE for measuring catapult choke ring axes
at various locations. The gage set consists of a gage case and
pelican case.
Gage Case
Two storage cases, the gage case and pelican case, are provided
for transporting and storing components of the gage set. The gage
case is the smaller of the two storage cases provided and is
designed to fit within the larger pelican case. The gage case
houses the measuring assembly and is to be used to protect the
measuring assembly when entering the water brake tank area. The
gage case is fitted with two foam inserts. When storing the
measuring assembly in the cage case, insert the gage body in the
smaller of the two circular cut outs in the foam in order to avoid
damaging the measuring assembly when the case is closed.
Pelican Case
The pelican case is comprised of two tiers. Each tier is fitted
with a foam cube-type insert with slots provided to house its
designated components. The top tier contains the master ring
(referred to as the
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Figure 3-34 Measuring assembly.
standard) and a battery charger. The bottom tier contains a
spare indicator and battery, along with a 1.5 millimeter (mm) Allen
drive, for installing/removing the indicator from the gage body,
and a spray can of rust inhibitor, for use on the master ring.
Measuring Assembly
The measuring assembly (Figure 3-34) is comprised of the
following components:
Gage body (gray)The gage body is the primary structure for the
measuring assembly. It provides the means of attaching the
indicator, battery and rotation knob. The gage body is designed to
be inserted into the choke ring and held in place by locating pins,
inserted through the stationary ring and into the choke ring. Two
access holes (portals) are provided in the gage body 180 degree
apart from one another to allow the indicator contacts to extend
through the gage body and ride against the internal surface of the
choke ring. The stationary ring has a reference compass divided
into 150 degree increments. The compass shall be used as a
reference when taking measurements.
NOTE
Choke ring gage set is a new special tool that replaces the
no-go gage used during choke ring reading.
3-20
-
Figure 3-35 Indicator.
Stationary ring (yellow) The stationary ring is attached to the
gage body and provides a means of centering the gage body in the
choke ring. Three locating pins are used to secure the stationary
ring and gage body to the choke ring. A retaining cable is provided
to prevent loss of locating pins.
Rotation knobThe rotation knob provides a means for the operator
to rotate the gage body around the inner circumference of the choke
ring. This action allows readings to be obtained at various
locations within the choke ring. These readings are then converted
and shown on the indicator in inches.
Indicator The indicator (Figure 3-35) is an inductive dial
comparator-type unit designed to measure in inches. The indicator
is mounted inside of the gage body and held in place by four
attaching screws. Extended up from the 12 oclock position on the
indicator is a spring-loaded rod with a contact point located on
the rod end. Extending down from the 6 oclock position is the
mounting shank, which contains a measuring spindle and a contact. A
rubber bellow is installed over the measuring spindle and mounting
shank to resist water intrusion. The two contacts extend through
the access holes (portals) located in the gage body. When the gage
body is rotated, the contacts ride around the inner circumference
of the choke ring, providing a means of obtaining dimensional
measurements. A 1.5mm Allen driver is provided for installing and
removing the indicator from the gage body.
Li-Ion batteryThe Li-Ion battery mounts to a mounting plate
attached to the inside of the gage body. The battery is secured to
the mounting plate by two thumbscrews. The battery is a
rechargeable Li-Ion (3.7 volt - 14.8 volt) battery pack that
provides power to the indicator and is equipped with a charging
receptacle for use with the battery charger. A power cable attached
to the battery provides the connection between battery and
indicator.
WARNING
Prior going inside the tank, ensure all tag-outs are in
accordance with the current shipboard instructions.
NOTE
Choke ring reading requires a QAI level of QA inspection. Refer
to the applicable QA card for specific QAI
requirements.
3-21
-
Figure 3-36 Battery charger.
Master Ring
A master ring provides the standard for zeroing-out the
indicator prior to each use. Unlike the previously used no-go gage,
the master ring does not have to be at the same temperature as the
choke ring; in fact, the closer it is kept to normal ambient room
conditions (70 degree Fahrenheit), the better. As long as the
measuring assembly, after being calibrated in the standard, is not
kept in a hot water brake tank for more than 1 hour prior to taking
readings, the accuracy of the measurements will not be
significantly affected.
Battery Charger
A battery charger (Figure 3-36) is provided to maintain the
battery in an operational condition. It detects battery pack
voltage and automatically shuts off when the battery is fully
charged. It also has a light-emitting diode (LED) to indicate
battery status, red while charging and green when fully
charged.
NOTE
The indicator display will be GREEN when values are within 7.918
to 7.935. If outside these specifications, the display
turns RED.
NOTE
Care should be taken to ensure that the master ring is as close
to ambient room temperature as possible.
Measurement of the ring temperature is not necessary.
3-22
-
Figure 3-37 Indicator set-up.
Use
The indicator must be calibrated or zeroed-out using the master
ring prior to accomplishing choke ring measurements. To zero-out
the indicator, follow the steps below.
1. Place the flat surface of the master ring on a flat, clean
surface (Figure 3-37), then insert the gage body into the master
ring ensuring the gage body is resting squarely.
2. Using the ON/OFF button on the indicator, place the indicator
to ON position.
3. Press the PRESET button; the indicator should indicate an
initial reading of 7.920 (plus/minus .00005). If the indicator does
not read 7.920, either replace the indicator or ensure the
indicator is calibrated.
4. If a good reading (7.920) is attained, remove the measuring
assembly from the master ring. The measuring assembly is now ready
for use.
After the indicator has been properly calibrated, follow the
steps below for choke ring measurements.
1. Remove the three locating pins from the stationary ring
(Figure 3-38) and carefully insert the gage body into the choke
ring.
2. With the indicator face orientated at the 12 oclock position,
as indicated by the red line on the gage body, carefully insert the
gage body into the choke ring.
3. Align the locating pin holes (smaller holes) with the nearest
corresponding holes in the choke ring. If necessary, rotate
stationary ring slightly in order to properly align holes in
stationary ring with holes in choke ring.
4. Ensure that the stationary ring is flush with the outermost
surface of the choke ring as shown in Figure 3-38, view A; using
the three locating pins, secure measuring assembly to choke ring as
shown in Figure 3-38, view B. Do not jam or force pins into the
choke ring holes. The pins should be inserted by hand until
snug.
5. Perform choke ring measurements.
NOTE
Applying any force to the rotation knob at the time of
measurement can result in inaccurate readings. Once
indicator contact is placed in position, release knob prior
noting reading.
3-23
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Figure 3-38 Choke ring measurement.
INVENTORY AND ACCOUNTABILITY
All measuring tools will be marked in some manner, (etched,
stenciled, etc.), to comply with standard inventory instructions.
These standard instructions may be found in Aircraft Launch and
Recovery Equipment (ALRE) Tool Control Manual, Naval Air
Engineering CenterMiscellaneous (NAECMISC) 51-OR732.
Some measuring tools such as tapes and calipers may be part of a
specific toolbox inventory. Other precision measuring instruments,
such as micrometers, snap gauges and vernier calipers, will
normally be maintained in the division's central tool room.
Regardless of the tool's permanent location, it is always the
user's responsibility to maintain, care for, and use the tool
properly.
Damage, loss, or an improperly working tool should be reported
immediately. Loss of a tool becomes especially critical when
working on or around the catapult or arresting gear machinery. The
tool may be "lost" in the machinery and, if not found, may cause
catastrophic damage to the equipment and serious injury to
personnel. Always double-check the inventory, ensuring every tool
is accounted for upon job completion. The proper tools will help
you maintain your equipment but only if you maintain your tools
properly.
SUMMARY
This chapter has introduced you to some of the most often used
measuring tools and the techniques for using them. Selecting the
proper tool, using and maintaining the various tools, and
inventorying the tools have all been discussed. By thoroughly
understanding and comprehending this chapter, you, as an ABE, will
be able to perform your daily duties more efficiently and
safely.
3-24
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End of Chapter 3
Measuring Tools and Techniques
Review Questions
3-1 How many graduated division marks are there in a rule?
A. 3 B. 4 C. 5 D. 6
3-2 What is a general rule in reading measurements?
A. Always increase fractions to their highest term. B. Always
reduce fractions to their highest term. C. Always reduce fractions
to their lowest term. D. Always increase fractions to their lowest
term.
3-3 What is attached at the end of the tape or rule and normally
part of the measurement?
A. Hook B. Base C. Body D. Spindle
3-4 What is the best and proper way of measuring bolts and
screws?
A. Holding them down against a flexible rule B. Holding them up
against a rigid rule C. Holding them up against a flexible rule D.
Holding them down against a rigid rule
3-5 How is an outside diameter of a pipe measured?
A. Using a flexible-type rule, line up the end of the rule with
one side of the pipe then swing the rule through an arc and take
the minimum reading.
B. Using a rigid rule, line up the end of the rule with one side
of the pipe then swing the rule through an arc and take the maximum
reading.
C. Using a rigid rule, line up the end of the rule with one side
of the pipe then swing the rule through an arc and take the minimum
reading.
D. Using a flexible-type rule, line up the end of the rule with
one side of the pipe then swing the rule through an arc and take
the maximum reading.
3-6 What type of caliper has legs with a spring hinge that are
linked by a screw?
A. Outside B. Inside C. Depth D. Spring-joint
3-25
-
3-7 How are calipers adjusted?
A. Pulling and pushing the legs to open or close them B.
Un-screwing the adjustable nut C. Loosening the adjustable screw D.
Pulling and pushing the head to open and close them
3-8 What is the other name of hermaphrodite caliper?
A. Spread-leg caliper B. Outward-leg caliper C. Odd-leg caliper
D. Aphrodite-leg caliper
3-9 What is hermaphrodite caliper usually used for?
A. Locating the center of a shaft or shoulder B. Locating the
length of the shaft C. Measuring the circumference of a shaft D.
Measuring the inside diameter of a shaft
3-10 What caliper is used for measuring inaccessible outside
dimensions?
A. Spring B. Firm-joint C. Solid D. Transfer firm-joint
3-11 What part of the caliper is tightened after taking the
measurement?
A. Lock joint B. Binding nut C. Firm joint D. Adjusting
screw
3-12 How many types of micrometer are there?
A. 2 B. 3 C. 4 D. 5
3-13 On a micrometer, how many threads per inch are on a
spindle?
A. 30 B. 40 C. 50 D. 60
3-26
-
3-14 What scale is used to obtain accurate measurements up to
ten-thousandths of an inch?
A. Spring scale B. Joint scale C. Vernier scale D. Depth
scale
3-15 What range of increments do the extension rods usually come
in?
A. 1 to 2 inches B. 1 to 2 inches C. 1 to 3 inches D. 1 to 3
inches
3-16 What is used to measure inside diameter of a pump casing or
cylinder?
A. Outside micrometer B. Inside micrometer C. Depth micrometer
D. Length micrometer
3-17 What micrometer is used to determine the pitch diameter of
a screw?
A. Outside B. Depth C. Inside D. Screw
3-18 How many equal parts is the thimble scale divided into?
A. 15 B. 20 C. 25 D. 30
3-19 In what training manual you can find tool descriptions and
instructions for their use?
A. NAVEDTRA 12085 B. NAVEDTRA 12805 C. NAVEDTRA 12058 D.
NAVEDTRA 12850
3-20 What is Aircraft Launch and Recovery Equipment (ALRE)
manual NAECMISC-51-OR732?
A. ALRE Corrosion manual B. ALRE Tool Control manual C. ALRE
Maintenance manual D. ALRE Quality Assurance manual
3-27
-
3-21 In the choke ring gage set, what is on the top tier of the
pelican case?
A. Indicator B. Master ring and battery charger C. No-go gage D.
Choke ring
3-22 In the choke ring gage set, what is on the bottom tier of
the pelican case?
A. 1.5 mm Allen wrench B. Thermometer C. Rotating knob D.
Caliper
3-23 What must be done to the indicator before taking choke ring
measurements?
A. Set to normal ambient room temperature B. Calibrated to zero
C. Verify it is clean and grease free D. Lock using locking pins to
master assembly
3-28
-
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3-29
CHAPTER 3MEASURING TOOLS AND TECHNIQUESLEARNING OBJECTIVESCOMMON
MEASURING TOOLSRules and TapesMeasuring ProceduresOutside Pipe
DiametersPipe CircumferencesInside DimensionsOutside
DimensionsDistance MeasurementsCare of Rules and Tapes
SIMPLE CALIPERSMeasuring Diameter of a Pipe or Thickness of Flat
ObjectMeasuring Distance between Two SurfacesMeasuring
Hard-to-Reach DimensionsMeasuring Hole DiametersSetting a
Combination Firm-Joint CaliperSetting Outside and Inside Spring
CalipersTransferring Measurements from One Caliper to
AnotherThickness (Feeler) Gages
MICROMETER CALIPERSTypes of MicrometersReading a
MicrometerOutside MicrometerReading the Vernier Scale on an Outside
MicrometerInside MicrometerReading an Inside MicrometerDepth
MicrometerReading a Depth MicrometerSelecting the Proper
MicrometerOther Special Measuring Tools
CHOKE RING GAGE SETGage CasePelican CaseMeasuring AssemblyMaster
RingBattery ChargerUseINVENTORY AND ACCOUNTABILITY
SUMMARYEnd of Chapter 3Measuring Tools and TechniquesReview
Questions
RATE TRAINING MANUAL User Update
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