1. MEASUREMENT OF SPECIMEN DIMENSIONS USING

LINEAR AND ANGULAR MEASUREMENT

INSTRUMENTS

AIM

To measure the various linear and angular dimensions of the given sample

specimens

EQUIPMENTS/MATERIALS

Outside micrometer, Vernier Caliper, Universal Bevel Protractor, hollow cylindrical

specimen and triangular specimen

PRINCIPLE

For Vernier Caliper,

Final reading = MSR + (VSR x LC)

Where,

MSR – Main Scale Reading

VSR – Vernier Scale Reading

LC – Least Count

For Outside Micrometer,

Final Reading = MSR + (CSR x LC)

Where,

MSR – Main Scale Reading

CSR – Circular Scale Reading

LC – Least Count

PROCEDURE

1. The various dimensions of the hollow cylindrical specimen are measured

using the vernier caliper. The outside jaws are used for measuring the outside

diameter and height of the specimen. The internal diameter is measured using

the inside jaws.

2. For the triangular specimen, the angles are measured using the universal bevel

protractor. The thickness of the specimen is measured using the outside

micrometer.

3. The observations are recorded in the tabular column and final dimensions are

measured according to the formulas in the principle.

4. Each dimension is measured 3 times and the average value is taken as the final

dimension.

OBSERVATIONS

a. Hollow Cylindrical Specimen (Least Count of Vernier = 0.02 mm)

Dimension Sl. No Vernier Readings Final Reading

(mm) MSR VSR

Outside

Diameter

1

2

3

Inside

Diameter

1

2

3

Height

1

2

3

b. Triangular Specimen

(Least count of Bevel protractor = 5 minutes)

Dimension Sl. No

Bevel Protractor

Readings Final Reading

(degree, minutes) Degree Minutes

Angle

ABC

1

2

3

Angle

ACB

1

2

3

(Least Count of Micrometer = 0.01mm)

Dimension Sl. No Micrometer Readings Total Reading

(mm) MSR CSR

Thickness

1

2

3

RESULTS

Hollow Cylindrical Specimen

1. Mean internal diameter (Di) = mm

2. Mean external diameter (Do) = mm

3. Height (H) = mm

Triangular Specimen

1. Angle ABC =

2. Angle ACB =

3. Thickness (t) = mm

A

B C

Fig. 1 Triangular Specimen

H

Do

Fig. 2 Cylindrical hollow Specimen

t

Di

2. MEASUREMENT OF GEAR TOOTH THICKNESS

AIM

To measure the gear tooth thickness of a given specimen gear.

EQUIPMENTS/MATERIALS

Profile Projector, Gear Tooth Vernier Caliper and Spur Gear specimen

PRINCIPLE

The main parameters determining the profile of a spur gear are: Pressure angle,

circular pitch, tooth thickness, crest circle and root circle diameter. The measuring

principle is based upon the determination of the exact depth „h‟ from the crest of the

tooth at which the chordal thickness should be measured. The correct depth ensures

that the chordal thickness is measured at the pitch circle. For spur gears,

h = m + (dp/2) [1 – cos (90o/Z)]

where,

m (module) = d0/(Z+2)

Z = number of teeth

dp = pitch circle diameter

Profile Projector is an optical device which is used to check profile of

components having special formed surfaces such as gears, screws and those objects

having regular or irregular profile. It has a high intensity light source. The light source

is placed on the principal focus of the collimating lens. The projection lens is a

combination of lenses and forms a real image of the object placed between it and the

collimating lens. The work-stage is 100x100 mm with micrometer screws. Two

digital micrometers are provided to control and measure the longitudinal and traverse

motion of the work table. It also comes with a digital display for 2 coordinate

displacement measurement and also angle measurement.

PROCEDURE

1. Count the number of teeth (Z) on the gear.

2. The outer diameter (do) of the gear was found using a vernier caliper.

3. The module is then calculated using the relation

m = do/ (Z+2)

4. The pitch circle diameter of the gear is calculated using the relation

dp = mZ

5. The chordal addendum (h) is calculated.

6. The gear tooth vernier has two scales, vertical and horizontal. The choral

addendum (h) is taken on the vertical scale and fixed. The vertical and

horizontal scale jaws are made to touch the top of the tooth and the chordal

tooth thickness was measured on the horizontal scale.

7. The reading was noted and the same procedure was repeated on other tooth

and the mean is taken.

8. The gear is placed on the work stage of the profile projector. The enlarged

profile of the gear is focused on the projector screen using the hand wheel on

the projector.

9. Tracing paper is fixed on the projection screen of the profile projector and the

image of the gear is traced using pencil.

10. Keeping the gear on the work stage as in the previous position, the tracing

paper is rotated upside down in such a way that the traced image mates with

the projected image of the gear to form a meshed gear system. Measurement

of gear thickness was done from the traced image of the gear.

11. The face width of the gear tooth is also measured using vernier caliper.

Fig.1 Gear Terminology

Fig. 2 Gear Tooth Vernier

OBSERVATIONS

Measurement of outer diameter of the gear (do)

(Least Count of Vernier = 0.02 mm)

Sl. No Vernier Reading Diameter

(do) (mm) MSR VSR

1

2

3

Mean outside diameter (do) =

Measurement of chordal thickness using gear tooth vernier

(Least Count of Vernier = 0.02 mm)

Sl. No

Vernier Reading Chordal

Thickness/ Gear

Tooth thickness

(tc) (mm)

MSR VSR

1

2

3

Mean Chordal Thickness =

Measurement of face width of gear tooth

(Least Count of Vernier = 0.02 mm)

Sl. No

Vernier Reading Width of gear

tooth

(w) (mm) MSR VSR

1

2

3

Mean face width of the gear tooth (w) =

RESULT

1. Outside diameter of the gear (do) = mm

2. Chordal thickness of the given spur gear

From, gear tooth vernier = mm

From, traced profile = mm

3. Face Width of the gear tooth (w) = mm

3. MEASUREMENT OF SURFACE ROUGHNESS

AIM

To study and determine surface roughness parameters using surface roughness tester.

APPARATUS

Surface roughness Tester, specimen

THEORY

The surface roughness measuring instrument traces the surfaces of various machine

parts, calculates their surface roughness based on roughness standards and displays

the results. A pick-up called the stylus attached to the detector unit will trace the

minute irregularities of the work piece surface. The vertical stylus displacement

during the trace is processed and digitally displayed on the liquid crystal display. The

tester can be operated in the measurement mode and calibration mode. The calibration

mode is set prior to measurement and performs calibration measurement. In the

measurement mode, the tester can start and stop measurements, calculate the

parameters and switch display contents and save measurement results.

PROCEDURE

1) Calibration: Calibration of a surface roughness measuring instrument is

performed by measuring a reference work piece (precision roughness

specimen)

(a) Press the [POWER/DATA] key to turn on the power.

(b) Press the [CAL/STD/RANGE] key. The calibration mode is entered. The current

calibration value is displayed. Check the displayed value against the value marked on

the roughness specimen. If they are the same value press the [n/ENT] key. If the

displayed value is different from that marked on the precision roughness specimen,

modify the calibration value. The following keys are used to enter a numeric value:

[CUTOFF] key to increment the numeric value; [mm/inch] key to decrement the

numeric value; [REMOTE] key for shifting the objective digit place for output;

[n/ENT] key for accepting the entered numeric value.

The entered calibration value is set.

(c) Place the precision roughness specimen and the calibration stage on a level table.

Set the tester so that the detector traversing direction is perpendicular to the cutter

mark of the precision roughness specimen. Press the [START/STOP] key. A

calibration measurement with the precision roughness specimen is performed. When

the calibration measurement has been completed, the measured value will be

displayed.

(d) Press the [n/ENT] key. The calibration factor is updated, completing the entire

calibration operation.

2) Measurement:

(a) To start the measurement set the tester on a work piece. For the surface

roughness measurement to be successful, it should be performed on a

firm base that is insulated from all sources of vibration. Confirm that

the stylus is in proper contact with the measured surface and that the

detector is parallel to the measured surface.

(b) Press the [START/STOP] key in the measurement mode. The detector

starts traversing to perform measurement. While the measurement is

being performed i.e., when the detector is traversing, “------“ is

displayed on the LCD. After the measurement has been completed, the

measurement result will be displayed on the LCD.

(c) The objective parameter to be displayed can be switched by pressing

the [PARAMETER] key while measurement result is being displayed

on the LCD. A measurement parameter is now displayed (say Ra).

Press the [PARAMETER] key until the desired parameter value is

displayed on the LCD. Each time the key is pressed, the displayed

parameter changes in the following order: Ra -> Ry -> Rz -> Rq-> Ra.

3) Modifying the cutoff length: The cutoff length can be switched to 0.8, 2.5, or

0.25 mm (0.03, 0.1, or.01”). For this, press the [CUTOFF] key in the

measurement mode. The cutoff length displayed changes in the following

order: 0.25 -> 0.8 -> 2.5mm, 0.01 -> 0.03 ->, 0.1 inch.

4) Modifying the number of sampling lengths: The evaluation length

(sampling length x number of sampling lengths) can be set by switching the

number of sampling lengths to either “1”, “3”, “5”, or “L”. If “L” is selected,

the evaluation length can be set as desired within the range between 0.3mm

and 12.5mm. Pres the [n/ENT] key in the measurement mode. Each time the

[n/ENT] key is pressed, the displayed number of sampling lengths changes in

the order 1 -> 3 ->5-> L->1.

5) Switching the roughness standard: In the measurement mode, press the

[CAL/STD/RANGE] key twice. The surface roughness standard set up mode

is entered. Press the [CUTOFF] key until the desired surface roughness

standard appears on the LCD. Each time the key is pressed the display

changes. Press the [n/ENT] key if the desired standard is selected. This accepts

the standard roughness standard.

OBSERVATIONS AND TABULATIONS:

Ground surface

Glass plate

Ra

Ry

Rz

Rq

Results

Surface

Ra

Rz

Rq

Glass plate

Ground surface

Inference:

4. MEASUREMENT OF THREAD

AIM

To measure the characteristics of the given external thread using Tool Maker‟s

Microscope.

EQUIPMENT

Externally threaded specimen and a Tool Makers Microscope

PRINCIPLE

A Tool Makers Microscope is essentially an optical microscope in principle. It has a

heavy base and on this, a worktable with a glass stage is supported on balls. The

longitudinal and traverse slide motion of the table is made possible by the micrometer

screws attached to the table. It is used for the magnified representation of the object

placed on the work-table. The elements of the external thread measured are: Major

diameter, minor diameter, pitch and thread angle. The major elements of an external

thread are shown in the figure.

PROCEDURE

In order to carry out the measurement, the threaded specimen is place on the work

table of the microscope. The crosswire is first made to coincide with the crest of the

thread on one side. The reading on the micrometer is noted and using the micrometer

head, the crosswire is made to coincide with the crest on the other side of screw and

reading is noted again. The difference between the readings gives the major diameter.

The same procedure is carried out to measure minor diameter (where the crosswire is

moved between the two roots of the thread) and pitch of the thread (where the

crosswire is moved between two adjacent crests)

The thread angle is measured by making use of the rotating crosswire which is

attached to a protractor. The crosswire is made to coincide with one slanting edge of

the thread and the Protractor readings are noted. Then the crosswire is made to

coincide with the adjacent side forming the thread angle and the protractor readings

are noted. The difference between the two readings will give the thread angle.

Fig. 3 Thread Terminology

OBSERVATIONS

Quantity

Measured

Micrometer Reading Difference

Initial Final

Major Diameter

Minor Diameter

Pitch

Quantity

Measured Readings

Vernier Reading Total

MSR VSR

Thread

Angle

Initial Reading

Final Reading

Thread angle = Initial reading – Final Reading

=

RESULT

The different thread characteristics measured are:

1. Major diameter = mm

2. Minor diameter = mm

3. Pitch = mm

4. Thread Angle =

5. MEASUREMENT OF TOOL SIGNATURE

AIM

To measure the tool signature of a single point cutting tool

APPARATUS

Tool maker‟s microscope, single point cutting tool

PRINCIPLE

The signature of the cutting tool is the systematic representation of the various angles

of the cutting tool and the nose radius. A tool maker‟s microscope is essentially an

optical microscope in principle. It has a heavy base and on this, a worktable with a

glass stage is supported on balls. The longitudinal and traverse slide motion of the

table is made possible by the micrometer screws attached to the table. It is used for

the magnified representation of the object placed on the work-table. The elements of

the tool signature which are measured are: Back rake angle, side rake angle, end relief

angle, side relief angle, end cutting edge angle and side cutting edge angle.

Fig. 4 Single Point Cutting Tool Geometry

PROCEDURE

In order to carry out the measurement, the tool specimen is placed on the work table

of the tool maker‟s microscope. One edge of the tool is made to coincide with one of

the cross wires of the eyepiece. The protractor reading is then set to zero. It is then

rotated such that one of the edges of the tool coincides with the cross wire. The

reading on the protractor is noted. The same procedure is repeated to measure the

other angles also.

OBSERVATIONS

Sl. No Angles

Initial

Reading Final Reading

Final

Measurement

1 Back Rake

2 Side rake

3 End/Front clearance

4 Side clearance

5 End cutting edge

6 Side cutting edge

7. Lip angle

RESULTS

The various cutting tool angle measured are:

1. Back Rake Angle =

2. Side rake Angle =

3. End/ Front clearance Angle =

4. Side clearance Angle =

5. End cutting edge Angle =

6. Side cutting edge Angle =

7. Lip Angle =