ent250: mechanical manufacturing skills ent 250: mechanical manufacturing skills (kemahiran...

ENT250: MECHANICAL MANUFACTURING SKILLS

ENT 250: MECHANICAL MANUFACTURING SKILLS

(KEMAHIRAN PEMBUATAN MEKANIKAL)


ENT250 : MECHANICAL MANUFACTURING SKILLS

• TIME: 8.00 AM – 11.00 AM, WEDNESDAYS AND THURSDAYS

• VENUE: ENGINEERING WORKSHOP & TEACHING FACTORY

• LECTURER: MR. AZIZUL MOHAMAD • PLVS: MR. AHMAD FAIZAL, MR. SYAYUTHI

& MR. ANUAR• TECHNICIANS: MR. ZALIZAM, MR. RIMI

RAFEEK & MR. NIZAM


• METROLOGY ( 1 WEEKS)

• CONVENTIONAL MANUFACTURING – – WELDING ( 2 WEEKS) – CONV. MILLING (2 WEEKS)– CONV. TURNING (2 WEEKS)

• COMPUTER-AGE MANUFACTURING– CNC TURNING (2 WEEKS)– CNC MILLING (2 WEEKS)– WIRE EDM (2 WEEKS)


• ASSESSMENT– 100% COURSEWORK, NO FINAL EXAM

• LAB REPORT

• TESTS AND QUIZZES

• ASSIGNMENTS

• CASE STUDY

• MINI PROJECT

• TEXTBOOK– TECHNOLOGY OF MACHINE TOOLS, 6TH ED.

KRAR, GILL & SMID. MCGRAW-HILL • SPECIAL PRICE: RM 75.00 (RRP RM130.00)

– LECTURE NOTES AND LAB MODULES


MEASUREMENT


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


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


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


Quantity Name Symbollength meter mvolume liter and lmass gram gtime minute min

second s

Following is list of some common SI quantities, names, and symbols you are likely to encounter when working in the machine shop.

Symbols for Use with SI


Quantity Name Symbolforce newton Npressure, stress pascal Patemperature degree Celsius °Carea square meter m2

velocity (speed) meters per minute m/minmeters per second m/s

angles degrees °minutes 'seconds ''

electric potential volt Velectric current ampere Afrequency hertz Hzelectric capacitance farad F


Symbols for Use with SI

Prefix Meaning Multiplier Symbolmicro one-millionth .000 001 µmilli one-thousandth .001 mcenti one-hundredth .01 cdeci one-tenth .1 ddeka ten 10 dahecto one hundred 100 hkilo one thousand 1 000 kmega one million 1 000 000 M

These prefixes often used with quantities: length, volume, mass, pressure, stress, area


BASIC MEASUREMENT


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


Inch System

Value Fraction Decimal

one-tenth 1⁄10 .1

one-hundredth 1⁄100 .01

one-thousandth 1⁄1000 .001

one ten-thousandth 1⁄10,000 .0001

one hundred-thousandth 1⁄100,000 .00001

one millionth 1⁄1,000,000 .000001


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 = 36 in.

1 m = 39.37 in.

1000 m = 1 km

1 km = 0.621 mi

1 mi = 1.609 km


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 0.30481 yd 914.4 91.44 9.144 0.9144


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


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.


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


Outside Calipers• Not precision tools• Used to approximately measure outside surface of

either round or flat work• Do not use when accuracy < .015 in.needed• Several styles

– spring joint

– firm joint

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


Inside Calipers

• Used to measure diameter of holes or width of keyways and slots

• Several styles– Spring joint– Firm Joint



MICROMETERS


Precision Measuring Tools

• Five categories of tools based on the dimension being measured– Outside– Inside– Depth– Thread– Height


Micrometer Caliper

• Standard inch micrometer accurate to .001 in.



Principle of the Inch Micrometer

• Two important thread terms– Pitch

• Distance from point on one thread to corresponding point on next thread

• Inch threads pitch expressed as 1/N(Number of threads)

• Metric threads expressed in millimeters

– Lead• Distance screw thread advances axially in one complete

revolution


Principle of the Inch Micrometer

• Zero line on thimble lined up with index line on sleeve (barrel)– Measuring faces just touch

• Pitch is 1/40 (.025) in. since 40 threads– One complete revolution of spindle, one line

appears– Every fourth line longer (represents .100 in.)

• Thimble has 25 equal divisions – Represents .001 in.


To Read Standard Inch Micrometer

• Note last number showing on sleeve and multiply by .100

• Note number of small lines visible to right and multiply by .025

• Note number of divisions on thimble from zero to line that coincides with index line on sleeve and multiply by .001

• Add three products to get total reading



Sample Reading

• Note last number showing on sleeve and multiply by .100


2 x .100

.200


Sample Reading

• Note number of small lines visible to right and multiply by .025


3

3 x .025

.075


Sample Reading

• Note number of divisions on thimble from zero to line that coincides with index line on sleeve and multiply by .001


13 x .001

.013


Sample Reading

• Add three products to get total reading


.200

.075

.013

.288 in.


Vernier Micrometer

Added to sleeve

Each division on vernierscale has a value of .0001 in.

Scale consists of 10 divisionsthat run parallel to index line.


Friction thimble


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


Metric Micrometer

• Similar to inch micrometer with two exceptions– Pitch of spindle screw (0.5 mm)– Graduations on sleeve and thimble

• Above index line on sleeve, graduations in millimeters (from 0 to 25) with every fifth line numbered

• Below index line, each millimeter subdivided into two equal parts of 0.5 mm

• Thimble circumference in 50 equal divisions (0.01mm)


To Read Metric Micrometer

• Note number of last main division showing above line to left of thimble

• Multiply that number by 1 mm• If there is half-millimeter line showing

below index line, between whole millimeter and thimble, add 0.5 mm

• Multiply number of line on thimble that coincides with index line times 0.01

• Add these products


Metric Vernier Micrometer

• In addition to graduations on standard micrometer, has five vernier divisions on barrel (each = .002 mm)

• Major division below index line – Each = 1 mm

• Minor division above index line – Each = .5 mm

• Fifty divisions around thimble – Each =0.1 mm)


Metric Vernier Reading

THIMBLE

SLEEVE0 8 6 4 2 00 5 10

35

30

25

20

15

10

5

MAJOR DIVISIONGraduation = 1mm

MINOR DIVISIONGraduation = 0.5 mm

VERNIER DIVISIONSEach division = 0.002 mm

Graduation = 0.01 mm

10 + 0 + .16 + .004 = 10.164


Combination Inch-Metric Micrometer


• Will give readings inboth inch and metric

• Digital reading forone system, standard barreland thimble reading for other

• Another type has dual scaleson sleeve and thimble


Testing Accuracy of Micrometers

• Test periodically to ensure accuracy• Clean measuring faces before testing• Turn thimble using friction thimble or

ratchet stop until measuring faces contact each other– Zero line on thimble coincides with center index

line on sleeve = accuracy

• Can also check by measuring gage block or other known standard


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


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.


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


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 addedprovides stand-aloneinspection system– Interface with PC



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



Screw Thread Micrometers

• Ranges stamped on micrometer frame• Metric available also in ranges

– 0-25 mm– 25-50 mm– 50-75 mm– 75-100 mm

• Helix angle of thread can give slightly distorted reading– First set thread micrometer to thread plug gage


VERNIER CALIPERS



Used to lock readings into place

Parts of the Vernier Caliper

Manufactured with both 25- and50-division vernier scales

Bar of 25-divisionvernier scale graduatedsame as micrometer


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.


Metric Vernier Caliper

• Many have both metric and inch graduations• Parts same as inch vernier• Main scale graduated in millimeters

– Every main division numbered, equal to 10 mm– Fifty graduations on sliding scale with every fifth

one numbered• 50 graduations occupy same space as 49 graduations

on main scale (49 mm)• 1 vernier division = 0.98 mm so difference between 1

main scale division and 1 vernier division = .02 mm


Reading a Metric Vernier Caliper

• Last numbered division on bar to left of vernier scale represents number of millimeters multiplied by 10

• Note how many full graduations showing between this numbered division and zero– Multiply number by 1 mm

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

• Add for total reading


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 to sliding jaw (and dial) used depth gage


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



FOR THE NEXT CLASS…• PLEASE GO TO THE RESPECTIVE

VENUE BASED ON YOUR GROUP:– GROUP A => ENGINEERING WORKSHOP,

PIC: MR ANUAR & MR SYAYUTHI– GROUP B => TEACHING FACTORY,

PIC: MR AHMAD FAIZAL & MR. AZIZUL

• ASSIGNMENT 1: PLEASE SEE PORTAL, DUE 26TH JULY 2006, 5.00 PM & MY OFFICE IN JEJAWI

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