measurement text book

7/30/2019 Measurement Text Book

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Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.

PowerPoint to accompany

Krar Gill Smid

Technology of Machine Tools6th Edition

Measurement

Section 5


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History

Egyptians used length called cubitEqual to length of forearm (middle finger to

elbow)

James Watt measured tolerances of steamengine with thickness of thin shilling

International System of Units (SI)developed in 1960

Two major systems of measurementInch system in US and Canada

Metric system for 90% of world


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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


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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, standardtaps, and screw thread sizes


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Krar Gill Smid


Basic Measurement

UNIT 7


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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


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Inch System

Unit of length is the inch

May be divided into fractional or decimal

fractionsFractional 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


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Inch System

Value Fraction Decimal

one-tenth 110 .1

one-hundredth 1100 .01

one-thousandth 11000 .001

one ten-thousandth 110,000 .0001

one hundred-thousandth 1100,000 .00001

one millionth 11,000,000 .000001


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Inch/Metric Conversion

Metric Size

mm cm dm m

1 in. 25.4 2.54 0.254 0.02541 ft 304.8 30.48 3.048 0.3048

1 yd 914.4 91.44 9.144 0.9144


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Fractional Measurement

Measured with rulers or calipers

Steel rules graduated

Binary-fractional divisions

1, , , 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 dimensionsof less than 0.50 mm


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Steel Rules

Metric steel rules graduated in millimetersand half-millimeters

Linear measurement without great accuracyLengths from 15 c. to 1 m.

Factional steel rules graduated in common

binary fractions (1/81/64 in.)Several varieties (spring-tempered, flexible,

narrow, and hook)

Lengths range from 1 to 72 in.


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Fractional Steel Rules

Spring-tempered quick reading 6 in. rules

Most frequently used in shop work

Hook rulesUsed to make accurate measurements from edge

of workpiece and also flanges and circular pieces

Use for setting inside calipers to a dimension

Decimal rulesUsed for linear measurements smaller

than 1/64 in.


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Fractional Steel Rules

Short-length rules

Used to measure small openings and hard-to-reach

locations Five small rules in set: range between and 1 in.

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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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


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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



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Using Outside Calipers

Hold both legs of caliper parallel to edge of rule.Turn adjusting nut until end of lower leg just splitsdesired graduation line on rule

Place caliper on workwith both legs of caliperat right angles tocenterline of the work

Diameter correct whencaliper just slides overwork by own weight


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Inside Calipers

Used to measure diameter of holes or width of

keyways and slots

Several stylesSpring joint

Firm Joint



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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 andone leg against flat surface

Hold legs of caliper parallel to edge of ruleand note reading


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Transferring Measurements

Check caliper setting with outside micrometerfor accurate measurement

Hold micrometer in right hand

Place one leg of caliperon micrometer anviland hold position

Rock top leg of caliper

in direction of arrowsAdjust thimble until

slight drag felt as caliper leg passed overmeasuring face



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Krar Gill Smid


Squares and

Surface PlatesUnit 8


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8-21

Objectives

The machinists combination square

Three types of solid and adjustable squares Two types of surface plates


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8-22

Square

Used for layout, inspection and setup

Manufactured to various degrees of

accuracy

Range from semiprecision to precision squares

Precision squares are hardened and

accurately ground

8 23


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8-23

Machinist's Combination Square

Used for quick check of 90 and 45 degree

angles and measure of length

Part of combination set that includes square

head, center head, bevel protractor and

graduated grooved rule

8 24


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8-24


8 25


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8-25

Precision Square

Used chiefly for inspection and setuppurposes

Hardened and accurately ground Must be handled carefully to preserve

accuracy

Great variety manufactured but all variationsof either solid square or adjustable square

8 26


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8-26

Beveled-Edge Square

Better quality standard squares used in

inspection

Beveled edge allows blade to make line

contact with work

More accurate check

Work is square (90 degrees) if both sides

touch surface of work

8 27


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8-27

Toolmaker's Surface

Plate Square

Provides convenient method of checking

work for squareness on surface plate One-piece construction

Little chance of any inaccuracy developing

8 28


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8-28

Adjustable Squares

Not as accurate as good solid square

Used where impossible to use fixed square

Diemaker's square

Used to check clearance angle on dies

Blade adjusted to angle of workpiece by blade-

adjusting screw, then angle checked withprotractor

Direct-reading type indicates angle of blade

8 29


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8-29

Adjustable Micrometer Square

Used to check part for squareness accurately


8 30


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8-30

Straightedges

Used to check surfaces for flatness and actas guide for scribing long, straight lines in

layout work Rectangular bars of hardened and accurately

ground steel

Edges flat and parallel Plain or beveled edges

Generally made of cast iron with ribs

8 31


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8-31

Surface Plates

Rigid block of granite or cast iron

Flat surface used as reference plane for layout

Generally have three-point suspension toprevent rocking when mounted on unevensurface

Two typesCast-iron plates

Granite surface plates


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Trivia (Extra Credit)

Why is a granite surface plate preferred?

8-33


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8-33

Surface Plates

Cast-iron plates

Well ribbed and high strength

Good wear-resistance qualitiesAfter machined, surface scraped by hand to flat

Operation long and cost high

Granite surface plates

Manufactured from gray, pink, or black granite

Several degrees of accuracy

Extremely flat finishes produced by lapping

8-34


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8-34

Advantages of Granite Plates

Not appreciably affected by temperaturechange

Will not burr, therefore, accuracy notimpaired

Nonmagnetic

Rustproof Abrasives will not embed themselves as

easily in the surface

8-35


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8-35

Care of Surface Plates

Keep surface plates clean at all times

Clean occasionally with solvent to remove film

Protect with wooden cover when not in use

Use parallels whenever possible to prevent

damage to plates by rough parts or castings

Remove burrs from workpiece before placing

it on plate

8-36


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8 36

Care of Surface Plates

Slide heavy parts onto the plate rather than

place them directly on the plate

Remove all burrs from cast-iron plates byhoning

When not in regular use, cover cast-iron

plates with thin film of oil to prevent rusting

Center punching or prick punching layout

lines should not be done on a surface plate


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Krar Gill Smid


Micrometers

Unit 9

9-38


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9 38

Objectives

Identify the most common types of outside

micrometers and their uses

Measure the size of a variety of objects towithin .001-in. accuracy

Read vernier micrometers to .0001-in.

accuracy Measure the size of a variety of objects to

within 0.01-mm accuracy

9-39


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9 39

Precision Measuring Tools

Five categories of tools based on the

dimension being measured

Outside

Inside

Depth

Thread

Height

9-40


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9 40

Micrometer Caliper

Standard inch micrometer accurate to .001 in.


9-41


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Principle of the Inch Micrometer

Zero line on thimble lined up with indexline on sleeve (barrel)

Measuring faces just touch Pitch is 1/40 (.025) in.since 40 threads

One complete revolution of spindle, one lineappears

Every fourth line longer (represents .100 in.)

Thimble has 25 equal divisions

Represents .001 in.

9-42


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To Read Standard Inch

Micrometer Note last number showing on sleeve and

multiply by .100

Note number of small lines visible to rightand multiply by .025

Note number of divisions on thimble from

zero to line that coincides with index line onsleeve and multiply by .001

Add three products to get total reading


9-43


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Sample Reading

Note last number showing on sleeve andmultiply by .100


2 x .100

.200

9-44


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Sample Reading

Note number of small lines visible to rightand multiply by .025


3

3 x .025

.075

9-45


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Sample Reading

Note number of divisions on thimble fromzero to line that coincides with index line on

sleeve and multiply by .001


13 x .001

.013

9-46


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Sample Reading

Add three products to get total reading


.200

.075

.013

.288 in.

9-47


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Vernier

MicrometerAdded to sleeve

Each division on vernier

scale has a value of .0001 in.

Scale consists of 10 divisions

that run parallel to index line.


Friction thimble

9-48


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To Read Vernier Micrometer

Read as would a standard micrometer

Note line on vernier scale that coincides with

one on thimble

Indicates number of ten-thousandths

Multiple the line number times .0001

Add to total of the other readings

9-49


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Micrometer Adjustments:

Remove Play in Threads

Back off the thimble

Insert C-spanner into slot or hole ofadjusting nut

Turn adjusting nut clockwise until play

between threads has been eliminatedNote: After adjusting, spindle should advance freely

while ratchet stop or friction thimble is being turned

9-50


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Testing Accuracy of Micrometers

Test periodically to ensure accuracy

Clean measuring faces before testing

Turn thimble using friction thimble orratchet stop until measuring faces contacteach other

Zero line on thimble coincides with center index

line on sleeve = accuracy

Can also check by measuring gage block orother known standard

9-51


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Adjusting Accuracy of a

Micrometer Clean measuring faces; inspect for damage

Close measuring faces carefully by turning

ratchet stop or friction thimble

Insert C-spanner into hole or slot in sleeve

Carefully turn sleeve until index line on

sleeve coincides with zero line on thimble

Recheck accuracy

9-52


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Special-Purpose Micrometers

Direct-reading micrometer

Additional digital readout

built into frame


Large-frame micrometer

Made for measuring large

outside diameters up to 60 in.Interchangeable anvils give

range of 6 in.

9-53


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Other Micrometers

Indicating micrometer

Uses indicating dial and movable anvil

Accurate to ten-thousandths of an inch

Can be used as a comparator with gage blocks


Mul-T-Anvil

micrometer Used for measuring tubing

and distances from a slot to

an edgeRound and flat anvils

9-54


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Digi-Matic Micrometer

Used as hand gage for inspecting small parts

Accurate up to 50 millionths of an inch and

displays both inch or metric sizes Statistical process

control when added

provides stand-aloneinspection system

Interface with PC


9-55


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Screw Thread Micrometers

Measures pitch diameter of threads

Pointed spindle and double-V swivel anvil

Shaped to contact pitch diameter of thread

Equal to outside diameter less depth of one thread

Limited to certain range

Four ranges for one-inch

8-13 TPI 14-20 TPI

22-30 TPI

32-40 TPI


P P i


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Copyright The McGraw-Hill Companies, Inc.

Permission required for reproduction or display.


Krar Gill Smid


Vernier Calipers

Unit 10

10-57


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Objectives

Measure workpieces to within an accuracy

of .001 in. using a 25-division inch vernier

caliper


of .001 in. using a 50-division inch vernier

caliper


of 0.02 mm using a metric vernier caliper

10-58


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Used to lock readings into place

Parts of the Vernier Caliper

Manufactured with both 25- and

50-division vernier scales

Bar of 25-division

vernier scale graduated

same as micrometer

10-59


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Measuring a Workpiece

Remove all burrs from workpiece

Clean surface to be measured

Open jaws enough to pass over work

Close jaws against work and lock right-handclamp screw

Turn adjusting screw until jaws just touch

work surface

Lock clamp screw on movable jaw

Read measurement

10-60


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Reading the Measurement



A 50-division inch vernier caliper reading of 1.464 in.

1 x 1.000= 1.000

4 x 0.100= .400

1 x 0.050= .050

14 x 0.001= .014

1.464 in.

10-61


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Metric Vernier Caliper

Many have both metric and inch graduations

Parts same as inch vernier

Main scale graduated in millimetersEvery main division numbered, equal to 10 mm

Fifty graduations on sliding scale with every fifthone numbered

50 graduations occupy same space as 49 graduationson main scale (49 mm)

1 vernier division = 0.98 mm so difference between 1main scale division and 1 vernier division = .02 mm

10-62


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Reading a Metric Vernier Caliper

Last numbered division on bar to left ofvernier scale represents number ofmillimeters multiplied by 10

Note how many full graduations showingbetween this numbered division and zero

Multiply number by 1 mm

Find line on vernier scale that coincides withline on bar and multiply by 0.02 mm

Add for total reading

10-63


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Direct-Reading Dial Caliper

Dial indicator, hand attached to pinion,

mounted on sliding jaw

Metric: 1 revolution of hand = 2 mm of travel Inch: 1 revolution = .100 or .200 in. of travel

Depends on manufacturer

Most have narrow sliding blade attached tosliding jaw (and dial) used depth gage

10-64


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Digital Electronic Caliper

Can provide readings to resolution of.0005 in. or 0.01 mm at touch of button

No rack, pinion or glass scale

Can connect to Statistical Process Control (SPC)equipment for inspection purposes

Measurements

Inside diameter

Outside diameter

Step

Depth





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Krar Gill Smid


Inside-, Depth-, and Height-

Measuring Instruments

Unit 11

11-66


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Transfer-Type Instruments

Size of object taken with instrument notcapable of giving direct reading

Small hole gages for small measures

Sets of four

Range: .125 - .500 in.



Have small, round end or ball Have flat bottom

11-67


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Transfer-Type Instruments

Telescope Gages

Used to obtain size of holes, slots, and recesses

from .3125 to 6.000 in.(8 to 152 mm)

T-shaped: pair of telescoping

tubes connected to handle

Knurled knob on handle end

locks plungers into position

11-68


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Vernier Height Gage

Precision instrument

Variety of sizes:

12-72 in. or 300-1000 mm.

Height within .001 in (0.02 mm) Digital height gage

zero function, display .0001 in.

Offset scriber

Attachment that permitssetting heights from face of plate

Depth gage attachment

11-69


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To Measure with a Vernier HeightGage and Dial Indicator

1. Thoroughly clean plate, base, work surface

2. Place finished edge of work on surface

plate3. Clamp against angle plate if necessary

4. Insert snug-fitting plug into hole with .500in projecting

5. Mount dial indicator on movable jaw6. Adjust movable jaw until indicator almost

touches surface plate

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To Measure with a Vernier Height

Gage and Dial Indicator7. Lock upper slide of height gage, use

adjusting nut to move indicator until dial

registers turn8. Set indicator dial to zero

9. Adjust vernier height gage until indicator

registers zero on top of plug10. Subtract initial reading plus half diameter

of plug

measurement text book

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