machining & metrology lab final

(Lab Technician) (Faculty-In-Charge)

GALGOTIAS UNIVERSITY

Greater Noida, Uttar Pradesh

School of Civil and Mechanical Engineering

Department of Mechanical engineering

LAB MANUAL

MACHINING PROCESSES

AND METROLOGY LAB

(MEE211L)


General laboratory safety

1. Wear safety glasses or face shields when working with hazardous materials and/or

equipment.

2. Wear gloves when using any hazardous or toxic agent.

3. Clothing: When handling dangerous substances, wear gloves, laboratory coats, and

safety shield or glasses. Shorts and sandals should not be worn in the lab at any time.

Shoes are required when working in the machine shops.

4. If you have long hair or loose clothes, make sure it is tied back or confined.

5. Do not use any equipment unless you are trained and approved as a user by your

supervisor.

6. Keep the work area clear of all materials except those needed for your work.

7. Equipment Failure - If a piece of equipment fails while being used, report it

immediately to your lab assistant or tutor. Never try to fix the problem yourself

because you could harm yourself and others.

8. If leaving a lab unattended, turn off all ignition sources and lock the doors.

9. Never pipette anything by mouth.

10. Clean up your work area before leaving.


GALGOTIAS UNIVERSITY

Greater Noida, Uttar Pradesh

School of Civil and Mechanical Engineering

LIST OF EXPERIMENTS

MACHINING PROCESSES AND METROLOGY LAB (MEE211L)

1. Calibration of the following instruments:

i. Calibration of Micrometer iii. Calibration of Dial Gauge

ii.Calibration of Vernier Caliper

2. Measurement of taper angle using Bevel Protractor

3. Measurement of taper angle using Sine Bar

4. Measurement of dimensions of given specimen using Tool maker’s microscope.

5. To measure various angles of single point cutting tool using profile projector

6. Study and understanding of limit, fit and tolerance

7. Experiments on Lathe to establish the cutting speed, feed and depth of cut on cutting

forces.

8. Study on Machining slots using shaping and slotting machines

9. Grinding of single point cutting tool as per given specifications (to check the tool angles).

10. Study on Electrical discharge machining and wire-EDM.


1. CALIBRATION OF PRECISION MEASURING

INSTRUMENTS

Aim:

To study and calibrate the precision measuring instruments like Vernier caliper, Micrometer,

and Dial gauge.

Apparatus Required:

Surface plate, Vernier caliper, Micrometer, Dial gauge, and Slip gauges.

Specification:

Vernier caliper Range: L. C:

Micrometer Range: L. C:

Dial gauge Range: L. C:

Study:

1.) Vernier caliper:

The Vernier caliper has one ‘L’ shaped frame with a fixed jaw on which Vernier scale is

attached. The principle of Vernier is that when two scale divisions slightly different in sizes can be

used to measure the length very accurately.

Least Count is the smallest length that can be measured accurately and is equal to the

difference between a main scale division and a Vernier scale division.

LEAST COUNT = 1 Main scale division – 1 Vernier scale division


Uses:

It is used to measure the external diameter, the internal diameter and the length of the

given specimen.

2.) Micrometer:

The micrometer has an accurate screw having about 10 to 20 threads/cm and revolves in a

fixed nut. The end of the screw is one tip and the other is constructed by a stationary anvil.

LEAST COUNT = Pitch scale division / Number of threads

Pitch scale division = Distance moved / number of rotation

Uses:

Outside micrometer is used to measure the diameter of solid cylinder.

Inside micrometer is used to measure the internal diameters of hollow cylinders and

spheres.

3.) Dial gauge:

The dial gauge has got 2 hands. The short hand reads in mm. One complete revolution of

long hand reads one mm. The plunger of the dial gauge has to be placed on the surface whose

dimension has to be read.

Least Count = One division of the circular scale with long hand.

Uses:

It is used as a mechanical comparator.


Procedure For Calibration:

1.) The range of the instruments is noted down. 2.) Within that range, slip gauges are selected. 3.) The measuring instrument is placed on the surface plate and set for zero and the slip gauges

are placed one by one between the measuring points (jaws of the instruments.) 4.) The slip gauge (actual) readings and the corresponding (observed) readings in the measuring

instruments are noted down and tabulated. Observation table

S.No

Slip Gauge

Reading –

(Actual)

In mm

Precision Measuring Instruments Reading (Observedl) in mm

Vernier Caliper Micro Meter Dial Gauge

MSR

(mm)

VSR

(div)

TR

(mm)

Error

(mm)

PSR

(mm)

HSR

(div)

TR

(mm)

Error

(mm)

SHR

(mm)

LHR

(div)

TR

(mm)

Error

(mm)

1

2

.

10

Result:

The precision measuring instruments are studied and calibrated.

Calibration graphs are then drawn for all measuring instruments between

1.) Actual value and Observed value. 2.) Actual value and Absolute error.


2. MEASUREMENT OF TAPER ANGLE USING BEVEL PROTRACTOR

Aim:

To measure the angles of given specimen using bevel protractor.

Apparatus Required:

Surface Plate, Dial Gauge, Slip Gauge, Bevel protractor, specimen

Theory

It is use for measuring &lying out of angles accurately and precisely within 5 minutes. The

protector dial is slotted to hold a blade which can be rotated with dial to the required angle and also

independently adjusted to any desired length. The blade can be locked in any position.

Procedure:

1. Initially bevel protractor is adjusted as per requirements. 2. Specimen is placed between the blades. 3. Reading noted directly from main scale and Vernier scale 4. For measuring, taper angle of sine bar, protractor is fixed to height gauge. 5. The protractor is corresponding adjusted. 6. Noted reading is tabulated.

Result:

Thus angle of given specimens was determined.


3. MEASUREMENT OF TAPER ANGLE USING SINE BAR

Aim:

To measure the taper angle of the given specimen using sine bar

Apparatus Required:

Surface plate, Dial gauge with stand, Sine bar, Slip gauge, Bevel protractor & specimen.

Theory:

The sine principle uses the ratio of the length of two sides of a right triangle in deriving a

given angle. It may be noted that devices operating on sine principal are capable of self generation.

The measurement is usually limited to 45 degree from loss of accuracy point of view. The accuracy

with which the sine principle can be put to use is dependent in practice, on some from linear

measurement. The sine bar itself is not complete measuring instrument. Another datum such as

surface plate is needed, as well as other auxiliary instrument, notably slip gauge, and indicating device

to make measurements.

Formula:

Taper angle ‘θ’ = Sin-1 (h/l) in degrees

Where, h = the total height (thickness) of the slip gauges in mm

l = the standard length of the sine bar in mm = 200mm


Procedure:

1. The taper angle of the specimen is first found out approximately with the help of a bevel protractor.

2. The sine bar is set at this angle on the surface plate with the help of the slip gauges as shown in the figure.

3. The specimen is placed on the sine bar so that its top taper surface is parallel to the surface plate.

4. The parallelism is checked and adjusted by increasing or decreasing the height level of the slip gauges, so that there should be no deflection in the long hand of the digital gauge when the spindle of the dial gauge is moved over the specimen surface.

5. The total height (thickness) of the slip gauges is noted down. 6. Trial readings are taken by placing the specimen at different points of the sine bar surface.

For Small Specimen:

Trial Total height of the slip gauge

Reading (mm)

1

For Large Specimen:

Trial h 1 (mm) h 2 (mm) h 2- h 1

(mm)

1

2

3

Result:

The taper angle of the given specimen is _________________________ degrees


4. MEASUREMENT OF DIMENTION OF GIVEN SPECIMEN USING

TOOL MAKER’S MICROSCOPE

Aim:

To measure various angles of single point cutting tool using Tool maker’s microscope.

Apparatus Required:

Tool maker’s microscope, Specimen, Eyepiece.

Theory:

Tool maker's microscope is versatile instrument that measures by optical means with no

pressure being involved it is thus a very useful instrument for making measurements on small and

delicates parts. The tool maker's microscope is designed for the following measurements;

measurements on parts of complex form for example, the profile of external thread as well as for

the tools, templates and gauges, measuring centre to centre distance of holes in any plane and other

wide variety of linear measurements and accurate angular measurements.

A tool maker's microscope is as shown in fig. The optical head can be moved up or down the

vertical column and can e clamped at any height by means of clamping screws. The table which is

mounted n the base of the instrument can be moved in two mutually perpendicular horizontal

directions (longitudinal and lateral) by means of accurate micromeres screws having thimble scale

and venires.


A ray of light from light source is reflected by mirror through 90. It is then passes through a

transparent glass plate (on which flat parts may be placed). A shadow image of the outline or

contour of the work piece passes through the objective of the optical head and is projected by a

system of three prisms to ground glass screen.

Observations are made through an eyepiece. Measurements are made by means of crosslines

engraved on the ground glass screen. The screen can be rotated trough 360 the angle of rotation is

read through an auxiliary eyepiece.

Procedure:

1. For taking linear measurements

The work piece is placed over the table. The microscope is focused and one end of the

work piece is made to coincide with cross line in the microscope (by operating

micrometers screws). The table is again moved until the other end of the work piece

coincide with the cross line on the screen and the final reading taken. From the final

reading, the desired measurement can be taken

2. Measurement of angle:

The screen is rotated until a line on the angle of screen rotation is noted. The screen is

further rotated until the same line coincides with the other flank of the specimen. The

angle of specimen on the screen will be difference in two angular readings.

Result:

The various parameters of the given specimen are measured.

Precaution:-

1) Obtain clean picture of cross line and the cross thread seen through the eyepiece.

2) For angular measurements lines must remain parallel to flank edge to the tooth.


5. MEASURMENT OF ANGLES USING PROFILE PROJECTOR

Aim:

To measure various angles of a given specimen using profile projector.

Apparatus required:

Contour projector and specimen.

Specification:

Contour projector magnification accuracy = ±0.1%

Micrometer Head = 0-25 mm L.C=0.1 mm

Colour illuminator = 150/250 W Halogen

Magnification = 10x, 20x, 50x lenses

Theory:

In contour illumination the light passes through the object to produce dark image of the

image contour by this source we can easily measure the external dimension of the object. In a

surface illumination light reflects over the object and again reflect back to the screen. Here we

can see the surface texture of the object. This is also very useful for comparison.


The screen has two cross hairlines marked on its centre which represents X and Y co

– ordinates with respect to the movement of micrometer stage. Measurements are taken with

one edge of the object coinciding with the respective cross hairline and then the micrometer

is rotated to bring the other edge of the object to coincide with the same cross hairline.

The screen also has graduated protractor rings for angular measurement through 360°. By

rotating the protractor we can set the cross hairline parallel to the object side and get the

differential readings. The work will be held on micrometer stage and focused on the screen

by means of vertical movement of stage until a sharp image of the object is obtained.

Procedure:

1. The required Magnification adapter is fixed in the center projector.

2. The flat specimen is placed on the glass plate and perfectly focused on the screen.

3. The profile of specimen is traced on a tracing paper is fixed on the screen using

pencil.

4. Then the angle between the two reference surface and dimension are measured

using table micrometer and the Rota table screen circular scale and are tabulated

Sl.no Angle Circular Scale

reading

Taper

Angle

Deg

Side Table

Micrometer

reading

Dimension

mm

Initial Final Initial Final

1 Α

A

2 Β

B

3 Γ

C

Result:

Thus the taper angle and other dimension of the given flat specimen is measured


6. Study and understanding of limit, fit and tolerance

Aim: Study and understanding of limit, fit and tolerance

INTRODUCTION

In manufacturing it is impossible to produce components to an exact size, even though

they may be classified as identical. Even in the most precise methods of production it would

be extremely difficult and costly to reproduce a diameter time after time so that it is always

within 0.01 mm of a given basic size. However, industry does demand that parts should be

produced between a given basic sizes. The difference between these sizes is called the

“tolerance” which can be defined as “the amount of variation in size which is tolerated”. A

broad, generous tolerance is cheaper to produce and maintain than a narrow precise one.

Hence one of the golden rules of engineering design is “always specify as large a tolerance as

is possible without sacrificing quality”. There are a number of general definitions and terms

which are used and these are described and illustrated below.

SHAFT

A shaft is defined as a member which fits into another member. It may be stationary

or rotating. The popular concept is a rotating shaft in a bearing. However when speaking of

tolerances the term “shaft” can also apply to member which has to fit into a space between

two restrictions, for example a pulley wheel which rotates between two side plates. In

determine the clearance fit for the boss is regarded as the “shaft”.

HOLE

A hole is defined as the member which houses or fits the shaft. It may be stationary or

rotating, for example, a bearing in which a shaft rotates is a “hole”. However, when speaking

of tolerances, thee term hole can be also apply to the space between two restrictions into

which a member has to fit, for example the space between two side plates in which a pulley

rotates is regarded as a “hole”.

Fig 1


BASIC SIZE

This is the size about which the limits of particular fit are fixed. It is the same for both

“shaft” and “hole”. It is also called the “nominal size” (Fig 1).

TOLERANCE

Tolerance is defined as the difference between maximum and minimum limits of size

for a hole or shaft. It is also the difference between the upper and lower deviations (Fig 1).

FIT

A fit may be defined as the relative motion which can exist between a shaft and hole

(as defined above) resulting form the final sizes which achieved in their manufacture. There

are three classes of fit in common use : clearance, transition and interference.

CLEARANCE FIT

This fit results when the shaft size is always less than the hole size for all possible

combinations within their tolerance ranges. Relative motion between shaft and hole is always

possible. The minimum clearance occurs at the maximum shaft size and the minimum hole

size. The maximum clearance occurs at the minimum shaft size and the maximum hole size.

TRANSITION FIT

A pure transition fit occurs when the shaft and hole are exactly the same size. This fit

is theoretically the boundary between clearance and interference and is practically impossible

to achieve, but by selective assembly or careful machining methods, it can be approached

within very fine limits. Practical transition fits result when the tolerance is such that the

largest hole is greater than the smallest shaft and the largest shaft is greater than the smallest

hole. Two transition fits are given on the data sheet. Relative motion between shaft and hole

is possible when clearance exists but impossible when interference exists.


INTERFERENCE FIT

This is a fit which always results in the minimum shaft size being larger than the

maximum hole size for all possible combinations within their tolerance ranges. Relative

motion between the shaft and hole is impossible. The minimum interference occurs at the

minimum shaft size and maximum hole size. The maximum interference occurs at the

maximum shaft size and minimum hole size. Two interference fits are given on the data

sheet, in table 1.

ALLOWANCE

Allowance is the term given to the minimum clearance (called positive allowance) or

maximum interference (called negative allowance) which exists between mating parts. It may

also be describe as the clearance or interference which gives the tightest possible fit between

mating parts.

Result :


7. Experiments on Lathe to establish the effect of cutting speed, feed

and depth of cut on cutting forces during turning


8. Study on Machining slots using shaping and slotting machines

AIM: Study on Machining slots using shaping and slotting machines

Theory:

Shaping Machine

The main functions of shaping machines are to produce flat surfaces in different

planes. Fig.1 shows the basic principle of generation of flat surface by shaping machine. The

cutting motion provided by the linear forward motion of the reciprocating tool and the

intermittent feed motion provided by the slow transverse motion of the job along with the bed

result in producing a flat surface by gradual removal of excess material layer by layer in the

form of chips. The vertical infeed is given either by descending the tool holder or raising the

bed or both. Straight grooves of various curved sections are also made in shaping machines

by using specific form tools. The single point straight or form tool is clamped in the vertical

slide which is mounted at the front face of the reciprocating ram whereas the workpiece is

directly or indirectly through a vice is mounted on the bed.

Fig.1 Principle of producing flat surface in shaping machine


Slotting machine:

Slotting machines can simply be considered as vertical shaping machine where the

single point (straight or formed) reciprocates vertically (but without quick return effect) and

the workpiece, being mounted on the table, is given slow longitudinal and / or rotary feed as

can be seen in Fig.2. In this machine also the length and position of stroke can be adjusted.

Only light cuts are taken due to lack of rigidity of the tool holding ram for cantilever mode of

action. Unlike shaping and planing machines, slotting machines are generally used to

machine internal surfaces (flat, formed grooves and cylindrical).

Shaping machines and slotting machines, for their low productivity, are generally used,

instead of general production, for piece production required for repair and maintenance. Like

shaping and slotting machines, planing machines, as such are also becoming obsolete and

getting replaced by plano-millers where instead of single point tools a large number of large

size and high speed milling cutters are used.


Working Principle:

The vertical slide holding the cutting tool is reciprocated by a crank and connecting rod

mechanism, so here quick return effect is absent. The job, to be machined, is mounted

directly or in a vice on the work table. Like shaping machine, in slotting machine also the fast

cutting motion is imparted to the tool and the feed motions to the job. In slotting machine, in

addition to the longitudinal and cross feeds, a rotary feed motion is also provided in the work

table.

The intermittent rotation of the feed rod is derived from the driving shaft with the help of a

four bar linkage as shown in the kinematic diagram.

It is also indicated in Fig.2 how the intermittent rotation of the feed rod is transmitted to the

lead screws for the two linear feeds and to the worm – worm wheel for rotating the work

table. The working speed, i.e., number of strokes per minute, Ns may be changed, if necessary

by changing the belt-pulley ratio or using an additional “speed gear box”, whereas, the feed

values are changed mainly by changing the amount of angular rotation of the feed rod per

stroke of the tool. This is done by adjusting the amount of angle of oscillation of the paul as

shown in Fig 2. The directions of the feeds are reversed simply by rotating the tapered paul

by 180o

as done in shaping machines.

Result: The study on Machining slots using shaping and slotting machines have been done

successfully.


9. Grinding of single point cutting tool as per given specifications

Aim: Grinding of single point cutting tool as per given specifications

Apparatus Required: grinding machine, workpiece

Theory:

There are two cutting edges on the tool bit. There is a cutting edge on the end of

the tool bit called the front cutting edge. There is also a cutting edge on the side of the

tool. Between these cutting edges is a rounded section of cutting edge called the nose.

Fig. Nomenclature of single point cutting tool


Procedure:

1. Grind the Front Relief

The first step in creating a tool bit is to grind the front relief. For most work, a relief

angle of 10° works well. While you are grinding the front relief, you are also creating

the front cutting edge angle. Make this angle about 10° also, so that the corner formed

by the front cutting edge and the side cutting edge is less than 90°.

2. Grind the Left Side Relief

Form the left side relief next. Again, create about a 10° angle. You don’t need to form

a side cutting angle. The side cutting edge can be parallel to the side of the tool blank

3. Grind the Top Rake

The top of the tool bit is ground at an angle that combines the back rake and the side

rake. The side rake is most important, because the side cutting edge does most of the

work. For cutting steel and aluminum, the side rake should be about 12° and the back

rake should be about 8°. For cutting brass, the rake angles should be much less, or

even 0°.

4. Round the Nose

A small nose radius allows you to turn into tight corners. A large nose radius produces

better surface finishes. Create a nose radius that is appropriate for the tool bit you are

creating.

Result: Grinding of single point cutting tool as per given specifications has been performed

successfully.


10. Study on Electrical discharge machining and wire-EDM

Aim: Study on Electrical discharge machining and wire-EDM

Electrical discharge machining

Introduction:

Electro Discharge Machining (EDM) is an electro-thermal non-traditional machining

process, where electrical energy is used to generate electrical spark and material removal

mainly occurs due to thermal energy of the spark. EDM is mainly used to machine difficult-

to-machine materials and high strength temperature resistant alloys. EDM can be used to

machine difficult geometries in small batches or even on job-shop basis. Work material to be

machined by EDM has to be electrically conductive.

Principles of EDM

Electrical Discharge Machining (EDM) is a controlled metal-removal process that is used to

remove metal by means of electric spark erosion. In this process an electric spark is used as

the cutting tool to cut (erode) the workpiece to produce the finished part to the desired shape.

The metal-removal process is performed by applying a pulsating (ON/OFF) electrical charge

of high-frequency current through the electrode to the workpiece. This removes (erodes) very

tiny pieces of metal from the workpiece at a controlled rate.

EDM Process

EDM spark erosion is the same as having an electrical short that burns a small hole in a piece

of metal it contacts. With the EDM process both the workpiece material and the electrode

material must be conductors of electricity. The EDM process can be used in two different

ways:

1. A preshaped or formed electrode (tool),usually made from graphite or copper, is shaped to

the form of the cavity it is to reproduce. The formed electrode is fed vertically down and the

reverse shape of the electrode is eroded (burned) into the solid workpiece.


2. A continuous-travelling vertical-wire electrode, the diameter of a small needle or less, is

controlled by the computer to follow a programmed path to erode or cut a narrow slot through

the workpiece to produce the required shape.

Conventional EDM

In the EDM process an electric spark is used to cut the workpiece, which takes the shape

opposite to that of the cutting tool or electrode. The electrode and the workpiece are both

submerged in a dielectric fluid, which is generally light lubricating oil. A servomechanism

maintains a space of about the thickness of a human hair between the electrode and the work,

preventing them from contacting each other.

In EDM ram or sinker machining, a relatively soft graphite or metallic electrode can be used

to cut hardened steel, or even carbide. The EDM process produces a cavity slightly larger

than the electrode because of the overcut.

Wire- EDM

The wire-EDM is a discharge machine that uses CNC movement to produce the

desired contour or shape. It does not require a special shaped electrode, instead it uses a

continuous travelling vertical wire under tension as the electrode. The electrode in wire-cut

EDM is about as thick as a small diameter needle whose path is controlled by the machine

computer to produce the shape required.

Fig. Wire EDM

The wire does not touch the workpiece, so there is no physical pressure imparted on the

workpiece compared to grinding wheels and milling cutters. The amount of clamping

pressure required to hold small, thin and fragile parts is minimal, preventing damage or

distortion to the workpiece. The accuracy, surface finish and time required to complete a job

is extremely predictable, making it much easier to quote, EDM leaves a totally random

pattern on the surface as compared to tooling marks left by milling cutters and grinding

wheels. The EDM process leaves no residual burrs on the workpiece, which reduces or

eliminates the need for subsequent finishing operations.


Wire EDM also gives designers more latitude in designing dies, and management more

control of manufacturing, since the machining is completed automatically. Parts that have

complex geometry and tolerances don't require you to rely on different skill levels or multiple

equipment. Substantial increases in productivity is achieved since the machining is untended,

allowing operators to do work in other areas. Most machines run overnight in a "lights-out"

environment. Long jobs are cut overnight, or over the weekend, while shorter jobs are

scheduled during the day.

Working principle of Wire EDM

The Spark Theory on a wire EDM is basically the same as that of the vertical EDM process.

In wire EDM, the conductive materials are machined with a series of electrical discharges

(sparks) that are produced between an accurately positioned moving wire (the electrode) and

the workpiece. High frequency pulses of alternating or direct current is discharged from the

wire to the workpiece with a very small spark gap through an insulated dielectric fluid

(water). Many sparks can be observed at one time. This is because actual discharges can

occur more than one hundred thousand times per second, with discharge sparks lasting in the

range of 1/1,000,000 of a second or less. The volume of metal removed during this short

period of spark discharge depends on the desired cutting speed and the surface finish

required. The heat of each electrical spark, estimated at around 15,000° to 21,000° Fahrenheit, erodes away a tiny bit of material that is vaporized and melted from the

workpiece. (Some of the wire material is also eroded away) These particles (chips) are

flushed away from the cut with a stream of de-ionized water through the top and bottom

flushing nozzles. The water also prevents heat build-up in the workpiece. Without this

cooling, thermal

expansion of the part would affect size and positional accuracy. Keep in mind that it is the

ON and OFF time of the spark that is repeated over and over that removes material, not just

the flow of electric current.

Application of Wire EDM

o Parts with complex geometry’s

o Parts requiring "tenths" tolerances

o Parts where burrs can’t be tolerated

o Thin or delicate parts that are susceptible to tool pressure

o Progressive, blanking and trim dies

o Extrusion dies

o Precious metals

o Narrow slots and keyways

o Tooling for forging, or injection molding operations.

o Medical and dental instrumentation

o Cutting hardened materials such as carbide, C.B.N. and P.C.D.

o Cutting difficult to machine materials like inconel and titanium

o Aerospace, defence and electronic parts

o Prototypes parts

o Production parts

o Form tools and inserts

o Electrodes (graphite or copper) for vertical EDM

Result: Study on Electrical discharge machining and wire-EDM have been done sucessfully.

machining & metrology lab final

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