1. Measurement
Section 5

2. History Egyptians used length called cubit
Equal to length of forearm (middle finger to elbow)
James Watt measured tolerances of steam engine with thickness of thin shilling
International System of Units (SI) developed in 1960
Two major systems of measurement
Inch system in US and Canada
Metric system for 90% of world

3. Metric (Decimal) Systems
Jan 16, 1970, Canada adopted SI for implementation throughout Canada by 1980
Dec 8, 1975, US Senate passed Metric Bill
Will take long time to convert
All machine tools and measuring devices will have to be redesigned
Long life expectancy of costly machine tools
People resistant to change

4. Inch/Metric Dimensioning 1994 ANSI Standards
Inch Dimensions
Zero not used before decimal point for values less than 1 inch
Dimension expressed to same number of decimal places as its tolerance
Metric Dimensions
Zero used before decimal point if < 1 millimeter
Whole number uses no decimal point nor zero
Decimal fraction of a millimeter – last digit to right of decimal point not followed by zero

5. Fractional/Inch System
Increased use of CNC and digital data make fractional sizes impractical
ANSI recommends decimal dimensions
Fractional dimensions still used to identify sizes of holes produced by drills, standard taps, and screw thread sizes

6. Symbols for Use with SI
Following is list of some common SI quantities, names, and symbols you are likely to encounter when working in the machine shop.
Quantity Name Symbol
length meter m
volume liter  and l
mass gram g
time minute min
second s

7. Quantity Name Symbol
force newton N
pressure, stress pascal Pa
temperature degree Celsius °C
area square meter m2
velocity (speed) meters per minute m/min
meters per second m/s
angles degrees °
minutes '
seconds ''
electric potential volt V
electric current ampere A
frequency hertz Hz
electric capacitance farad F

8. Symbols for Use with SI
These prefixes often used with quantities: length, volume, mass, pressure, stress, area
Prefix Meaning Multiplier Symbol
micro one-millionth µ
milli one-thousandth m
centi one-hundredth c
deci one-tenth d
deka ten da
hecto one hundred h
kilo one thousand k
mega one million M

9. Basic Measurement
UNIT 7

10. Objectives Identify several types of steel rules
Measure round and flat work to 1/64-in. accuracy with a rule
Measure with spring calipers and a rule
OBJECTIVES

11. Inch System Unit of length is the inch
May be divided into fractional or decimal fractions
Fractional system based on binary system
Common fractions: 1/2, 1/4, 1/8, 1/16, 1/32, 1/64
Decimal-fraction system uses base 10
Number written as product of 10 or fraction of 10

12. Inch System Value Fraction Decimal one-tenth 1⁄10 .1
one-hundredth 1⁄
one-thousandth 1⁄
one ten-thousandth 1⁄10,
one hundred-thousandth 1⁄100,
one millionth 1⁄1,000,

13. Metric System
Linear dimensions expressed in multiples and submultiples of meter
Millimeter most common
Fractions of millimeter expressed in decimals
Brief comparison of common inch and metric
1 yd in.
1 m in.
1000 m km
1 km mi
1 mi km

14. Inch/Metric Conversion
Metric Size
mm cm dm m
1 in
1 ft
1 yd

15. Fractional Measurement
Measured with rulers or calipers
Steel rules graduated
Binary-fractional divisions
1, ½, ¼, 1/8, 1/16, 1/32, 1/64
Decimal fractional divisions
decimeters, centimeters, millimeters, half-millimeters
1/64 in. or 0.50 mm. smallest used
Precision instruments
Micrometers and verniers used for dimensions of less than 0.50 mm

16. Steel Rules
Metric steel rules graduated in millimeters and half-millimeters
Linear measurement without great accuracy
Lengths from 15 c. to 1 m.
Factional steel rules graduated in common binary fractions (1/8 – 1/64 in.)
Several varieties (spring-tempered, flexible, narrow, and hook)
Lengths range from 1 to 72 in.

17. Fractional Steel Rules
Spring-tempered quick reading 6 in. rules
Most frequently used in shop work
Hook rules
Used to make accurate measurements from edge of workpiece and also flanges and circular pieces
Use for setting inside calipers to a dimension
Decimal rules
Used for linear measurements smaller than 1/64 in.

18. Fractional Steel Rules
Short-length rules
Used to measure small openings and hard-to-reach locations
Five small rules in set: range between ¼ and 1 in.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19. Measuring Lengths Fairly accurate measure with steel rules
Butt end of rule against shoulder or step
Steel rules become worn with constant use
Can make measurements taken from end inaccurate
Compensate by measuring from 1-in or 1-cm mark and subtracting 1 from measurement
Keep edge of rule parallel to edge of work
Rule used as straightedge to test flatness of workpieces
Edges ground flat: place, hold to light and view

20. Outside Calipers Not precision tools
Used to approximately measure outside surface of either round or flat work
Several styles
spring joint
firm joint
Do not use when accuracy < .015 in.needed
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21. Using Outside Calipers
Hold both legs of caliper parallel to edge of rule. Turn adjusting nut until end of lower leg just splits desired graduation line on rule
Place caliper on work with both legs of caliper at right angles to centerline of the work
Diameter correct when caliper just slides over work by own weight

22. Inside Calipers
Used to measure diameter of holes or width of keyways and slots
Several styles
Spring joint
Firm Joint
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

23. Measuring An Inside Diameter
Place 1 leg of caliper near hole's bottom edge
Hold caliper leg in position with finger
Keep caliper legs vertical or parallel to hole
Move top leg in direction of arrows and turn adjusting nut until slight drag felt on leg
Find size of setting by placing end of rule and one leg against flat surface
Hold legs of caliper parallel to edge of rule and note reading

24. Transferring Measurements
Check caliper setting with outside micrometer for accurate measurement
Hold micrometer in right hand
Place one leg of caliper on micrometer anvil and hold position
Rock top leg of caliper in direction of arrows
Adjust thimble until slight drag felt as caliper leg passed over measuring face
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.