Precision Measuring Tools Basic
Participant Self-Paced
Workbook
Introduction
Course Purpose
The purpose of this course is to introduce you to precision measuring tools.
In this course you will learn about decimals and tolerances as well as how to
use the following tools:
• Twelve-Inch Scale
• Six-Inch Dial Caliper
• Outside Micrometer (0-1) inch
• Ball Gauges
Once you complete a topic, a skill check is available for you to demonstrate
what you have read and practiced.
Check your answers with those that are provided to see how well you
understood the material.
Topics Covered
• Determining Decimals and Tolerances
• Using a Twelve-Inch Scale
• Using a Six-Inch Dial Caliper
• Measuring with an Outside Micrometer (0-1) inch
• Using Ball Gauges with a Micrometer
Course Objectives
At the end of this course, you will be able to:
Add and subtract decimals and determine the tolerance
range of given dimensions.
Use the following pieces of equipment to measure objects:
• Twelve-Inch Scale
• Six-Inch Dial Caliper
• Outside Micrometer (0-1) inch
• Ball Gauges
Objectives Measurement
Your understanding of the section objectives will be measured by your
participation in the following activities:
• Demonstrating how to add decimals and determine the tolerance of a
given number.
• Converting fractions to decimal equivalents by using a Decimal
Equivalents Card
• Using a scale to determine the correct length of several items.
• Using a Six-Inch dial caliper to determine the inside, outside, and
depth measurements of various items.
• Using an outside micrometer to measure various items.
• Using ball gauges and a micrometer to measure hole sizes and check
for hole size consistency.
Each section contains Skill Checks to assess your progress. A
comprehensive Final Test is administered at the completion of the sections.
You will be required to achieve a grade of 80% or better in order to pass
the Final Test.
Materials
To complete this course you will be given the following:
• A Student Guide
• A calculator
• Pencils
• Magnifying glass
• Decimal Equivalents Card
• Twelve inch Scale
• 0-1 inch outside Micrometer
• Six-Inch Dial Caliper
• Ball Gauges
• Test kits containing items to measure
• Final Test.
New Terminology
Tolerance – The degree of accuracy required for a dimension, expressed as
‘plus or minus’ (+/-) a specific amount.
Graduation – Marks on an instrument or tool that measure degree or
quantity.
Nominal – The dimension or quantity called out on an Engineering drawing
S E C T I O N 1: U S I N G D E C I M A L S
AND
TOLERANCES
Introduction
To perform fabrication work, you must understand decimal notation and
tolerances. In this section, you will learn about the decimal system and
practice performing math operations with decimals.
Objectives At the end of this section, you will be able to:
• Convert fractions to decimal equivalents
• Add and subtract decimals.
• Determine the tolerance range (upper and lower boundaries) of
given dimensions.
Resources
• Calculator
• Decimal Equivalents Card
Decimal Values
Linear dimensions on all Boeing drawings are expressed in decimal notation.
This system allows engineers to clearly specify the degree of accuracy, or
tolerance that is required for any dimension. Most linear measuring tools
used in manufacturing companies read in decimals. It is therefore important
that you be able to read and calculate decimals.
In decimal notation, inches are written to the left of a decimal point, while
fractions of an inch are written to the right of a decimal point and are
expressed in units of 10.
For example:
100. = One hundred inches
10. = Ten inches
1. = 1 inch
.1= one-tenth of an inch
.01= one-hundredths of an inch
.001= one-thousandths of an inch
.0001= one-ten thousandths of an inch
The first number to the right of the decimal point is in tenths of an inch.
There are 10 tenths in one inch. (.1000 x 10 = 1 inch). On the shop floor it is
pronounced as one tenth of an inch.
The second number to the right of the decimal is in hundredths of an inch.
There are 100 hundredths in one inch (.0100 x 100 = 1). The number .010 is
pronounced one hundredth of an inch.
The third number after the decimal is in thousandths of an inch and there are
1000 of them in one inch (.0010 x 1000 = 1 inch). The number .001 is
pronounced one thousandth of an inch.
When dimensions are carried out to four decimal places, it
is called ten thousandths of an inch. There are 10,000 of
these in each inch. (.0001 x 10,000 = 1 inch).
Review
The common shop way to read numbers is shown for each of the numbers
below.
• 2.8576
Two and Eight Hundred Fifty-Seven Thousandths and
Six-Tenths inches
• 4.050
inch
Four and Fifty-Thousandths inches
• .0687
inch
Sixty-Eight Thousandths and Seven-Tenths inch
• .500
inch
Five-Hundred Thousandths inch
• .0067
inch
Six-Thousandths and Seven-Tenths inch
Skill Check 1
Write out how you would say each number in shop language on the line
provided. When you are done, check your answers against the answers on
the following page.
1. .451
______________________________________________
______________________________________________
2. .897
______________________________________________
______________________________________________
3. 5.155
______________________________________________
______________________________________________
4. 7.1544
______________________________________________
______________________________________________
5. 3.2563
______________________________________________
______________________________________________
Skill Check 1
Answers - Check your answers from the previous page.
1. Four hundred fifty-one thousandths
2. Eight hundred ninety-seven thousandths
3. Five and one hundred fifty-five thousandths
4. Seven and one-hundred fifty-four thousandths and four-tenths
5. Three and two-hundred fifty-six thousandths and three-tenths
Converting Fractions to Decimal Equivalents
In most cases, a measurement requirement will be given to you in a decimal
format. By using the Decimal Equivalents Card you can easily convert a
fraction to a decimal. Simply find the fraction on the left side of the card and
read its decimal equivalent on the right side of the card. For example, ¼” is
the same as .250”.
Converting Fractions to Decimals
Exercise #1
You are asked to get a 5/16 drill bit. Because drill bits are usually measured in
decimal sizes, you look at your drill card and notice that 5/16” corresponds
with .3125 inches. When you go to the tool issue area, you ask for a .3125
drill bit rather than a 5/16.
Using your Decimal Equivalents Card, practice doing a few conversions in
the exercise below. The answers are provided to assist you in making these
conversions and understanding how to use the card.
Fraction
3/8
13/16
1/8
Decimal Equivalent
.3750
.8125
.1250
If you need help to complete this exercise, ask your facilitator for assistance.
Continue practicing until you are comfortable with the conversion process.
Skill Check 2
Convert the fractions listed below to decimal equivalents.
Check your answers on the next page.
1. 7/16 is equivalent to ______________
2. 9/32 is equivalent to ______________
3. 3/8 is equivalent to _______________
4. 25/64 is equivalent to ______________
5. 15/16 is equivalent to ______________
6. 1/2 is equivalent to ________________
7. 3/32 is equivalent to _______________
Skill Check 2 Answers
Listed below are the answers to the Decimal Conversion
Skill Check from the previous page.
1. .4375
2. .2812
3. .3750
4. .3906
5. .2344
6. .5000
7. .0938
If you are comfortable with converting fractions to decimals with the
Decimal Equivalent Card, move on to the next subject. If you are unsure of
the conversion process, have your facilitator assist you.
Dimensions & Tolerances
Now that you have learned how to add and subtract decimals, it’s time to
apply your knowledge to Dimension Tolerances.
A dimension listed on a drawing is called a nominal dimension. Tolerances
tell us how much discrepancy is allowed from the nominal dimension.
How much tolerance is allowed for a dimension is indicated by a plus (+) or
minus (-) sign. The following are examples of tolerances, starting with ‘plus
or minus four ten thousandths’.
• +/- .0004
• +/- .008
• +/- .01
• +/- .3
Drawing Tolerances
To determine the biggest dimension allowable, add the tolerance to the
nominal dimension. To determine the smallest dimension allowable, subtract
the tolerance from the nominal dimension.
Example:
A drawing requires a hole to be .39” from the edge. The tolerance is +/.03”.
To find the biggest dimension allowable, add .03 to .39.
.39
+ .03
.42
To find the smallest dimension allowable, subtract .03 from .39
.39
- .03
.36
For the nominal dimension of .39” in this drawing, the largest allowable
dimension is .42”. The smallest allowable dimension is .36”.
Skill Check 3
Determine the largest and smallest acceptable dimensions for the numbers
below and write your answers in the space provided. When you are finished,
check your answers against the Skill Check answer key on the next page.
If you would like more decimal practice, review this section and then
complete the Optional Skill Check that follows the Skill Check 3 answer
key.
a. 6.305 +/- .010
Largest
_____________
Smallest
_____________
b. 12.430 +/- .03
_____________
_____________
c. .097 +/- .005
_____________
_____________
d. 5.0 +/- .1
_____________
_____________
e. 28.78 +/- .03
_____________
_____________
f. 72.229 +/- .010
_____________
_____________
g. 16.432 +/- .002
_____________
_____________
h. .250 + 001/ -.000
_____________
_____________
i. 5.97 +.00/-.03
_____________
_____________
j. 1.402 +.10/-.00
_____________
_____________
k. 1.562 +/- .000
_____________
_____________
Skill Check 3 Answers
Check your numbers with the answers below.
a. 6.305 +/- .010
Largest
6.315
b. 12.430 +/- .03
12.460
12.400
.102
.092
5.100
4.900
e. 28.78 +/- .03
28.810
28.750
f. 72.229 +/- .010
72.239
72.219
g. 16.432 +/- .002
16.434
16.430
.251
.250
i. 5.97 +.00/-.03
5.970
5.940
j. 1.402 +.10/-.00
1.512
1.402
k. 1.562 +/- .000
1.562
1.562
c. .097 +/- .005
d. 5.0 +/- .1
h. .250 + 001/ -.000
Smallest
6.295
S ECTION2 : USING
A
SCALE
Introduction
Many manufacturing jobs require you to perform measurements using a
scale. In this section you will:
• Learn how to read a scale
• Measure several manufacturing parts
• Perform five Skill Checks
Objectives
At the end of this section, you will be able to:
• Use a Scale to measure specific manufacturing parts in inches.
Resources
• Six-Inch Scale
• Sharpened pencil
• Various manufacturing parts
Introduction
In this section you will be using a Six-Inch Scale.
Most scales have fractions marked on one face (halves, quarters, sixteenths
of an inch) and decimals marked on the other face (tenths and hundredths of
an inch). Since Engineering drawings use decimals, we will be using the
face that is marked with decimal measurements.
Decimal Scale
Fractional Scale
Reading the Scale
Study the figure below to become familiar with the graduations on a scale.
*Decimal Scale in 50ths of an inch graduations
To read a scale, place the scale against the item to be measured, and follow
these four steps:
1.) Read and record the closest value to the left in inches (1,2,3, etc.)
2.) Read and record the closest value to the left in tenths of an
inch (.1, .2, .3, etc.)
3.) Read and record the closest value to the left in hundredths of an
inch (.01, .02, .03, etc.)
4.) Add these numbers to determine the complete measurement.
If the reading line falls exactly on an inch mark or tenth of an inch mark,
record that number. Don’t record the number to the left.
Example: If the reading line fell between 2 and 3 inches at exactly three
tenths, the measurement would be 2.30”.
Also note that you would not record hundredths of an inch because the
reading was exactly on the three tenths line.
Skill Check 1
Calculate the reading on the scale below and record your answer on the line
below.
A. ___________
B. ___________
C. ___________
D. ___________
A
B
C
D
E
Skill Check 1 Answers
A.
B.
C.
D.
E.
0.240
0.760
1.000
1.630
2.380
Notice that zeroes have been added to the end of some of the answers.
Remember that this does not change the value of the numbers.
“Burning an Inch”
Many people prefer to start a measurement at the one-inch mark, as shown
in below. This practice is called ‘burning an inch’ and provides a more
accurate measurement if the end of your scale is in poor condition.
When burning an inch, be sure to subtract an inch from your reading.
S E C T I O N 3: U S I N G S I X - I N C H D I A L C A L I P E R S
Introduction
In this section you will learn how to read and use a Six-Inch Dial Caliper.
The Dial Caliper is used to measure inside measurements, outside
measurements, round stock, square stock, plates, counter bores, bushings
and depths.
Objectives
Each participant will be able to:
• Use a Six-Inch Dial Caliper to take inside and outside measurements
that are accurate to within +/- .005.
• Demonstrate how to determine the accuracy of a Six-Inch Dial
Caliper.
Skill Check
At the end of this section, you will be expected to use a Six-Inch Dial
Caliper to accurately measure objects to 3 decimal places.
Resources
• Six-Inch Dial Caliper
• Manufacturing parts to measure
Dial Caliper Introduction
A Six-Inch Dial Caliper is a precision-measuring tool that measures
accurately to within .001 of an inch. Although it is not as accurate as a
Vernier Scale Micrometer (which can read to within .0001 of an inch), the
Six-Inch Dial Caliper is more versatile.
You can use the Six-Inch Dial Caliper to measure distance from 0 to 6
inches for inside, outside, and depth measurements. Because of its
versatility, you will use this tool frequently.
A Dial Caliper has jaws that contact inside and outside surfaces during
measurements, and a rod connected to a slide for obtaining depth
dimensions. The end of the rod is notched to provide a nib for measuring
small grooves and recesses.
All readings are taken directly from the bar and dial-indicator. Knurled
thumbscrews lock the movable jaw and adjustable indicator dial.
With the addition of a depth attachment, the Dial Caliper becomes as
convenient and easy to use as a depth gauge.
Parts of the Dial Caliper
The major parts of the Dial Caliper are labeled on the diagram and described
below:
A. Bar: A scale with graduations in inches and tenths of an inch.
B. Fixed Jaws: Located at the zero end of the scale on the bar, the
fixed jaws function as the starting points for inside and outside
measurements.
C. Moveable Jaws: Can be slid along the bar in order to take inside
and outside readings.
D. Dial: The dial hand makes one complete revolution for each .10
inch of movement. The face is divided into increments of .001.
E. Moveable Jaw Clamp Screw: This locks the movable jaws into
place.
F. Adjusting Nut: This is used to adjust to the dial so that it registers
zero when the caliper jaws are closed.
G. Depth Bar: Used to take depth measurements of holes, steps, and
recesses.
Reading the Dial and Bar
Once you have placed the jaws in the space or around the part that you want
to measure, you need to read both the bar and the dial to get a reading.
The bar is in increments of inches and tenths. As you slide the bar to the
right, new increments appear from under the dial. In Figure 4- 2, the reading
is something over .700”.
One full rotation of the dial (zero to zero) represents a movement of .100
inch. The dial reads in thousandths and ten thousandths.
In the above picture, the last line visible on the bar is .700 and the dial reads
.050, so the reading on this measurement is .750.
In this example, the bar reads 3 tenths and the dial reads 12 thousandths, so
the reading is:
.300 + .012 = .312”
Skill Check 1 - Dial Caliper
Read the bar and dial in each photo below, then record your reading in the
space provided. When you are done, check your answers with the answer
key following this Skill Check.
1. This reading is :_________________ inches.
2. This reading is :_________________ inches.
1. 3. 3. This reading is :________ inches.
2. 3. 4. This reading is :________ inches.
3. 3. 5. This reading is :________ inches.
4. 3. 6. This reading is :________ inches.
5. 3. 7. This reading is :________ inches.
6. 3. 8. This reading is :________ inches.
7. 3. 9. This reading is :________ inches.
8. 3. 10. This reading is :________ inches.
Skill Check 1 Answers
Below are the answers to the previous exercise. How did you do? If you
missed more than 3 you may want to do a little more practice reading the
dial. If you got them all right, congratulations!
1. .966
2. .357
3. .665
4. .485
5. 1.003
6. 1.321
7. 1.100
8. .927
9. 1.490
10. 1.173
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