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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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Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
PowerPoint to accompany
Krar Gill Smid
Technology of Machine Tools6th Edition
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
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
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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
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
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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
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
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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
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
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
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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Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
PowerPoint to accompany
Krar Gill Smid
Technology of Machine Tools6th Edition
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.
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
9-43
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Sample Reading
Note last number showing on sleeve andmultiply by .100
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2 x .100
.200
9-44
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Sample Reading
Note number of small lines visible to rightand multiply by .025
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
13 x .001
.013
9-46
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Sample Reading
Add three products to get total reading
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
.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.
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
P P i
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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
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
Measure workpieces to within an accuracy
of .001 in. using a 50-division inch vernier
caliper
Measure workpieces to within an accuracy
of 0.02 mm using a metric vernier caliper
10-58
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Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
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
Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
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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
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.
Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
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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Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
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
11-70
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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