GOVERNMENT POLYTECHNIC
AHMEDABAD
UNIT:02
MEASUREMENT OF GEOMETRICAL
TOLERANCE
Presented By: Prof.Nirav N Patel
LME
LEARNING OUTCOMES
OF THIS SESSION
• Explain Working Of Dial Indicators.
• Select The Measuring Method And
Describe The Measurement Procedure
For Geometrical Tolerance Of Given
Part/Assembly.
SESSION OUTLINE
• RECALL CONCEPT
• WORKING AND USE OF DIAL INDICATOR.
• CONCEPT OF
STRAIGHTNESS,FLATNESS,ROUNDNESS AND
SQUARENESS.
• TESTING OF
STRAIGHTNESS,FLATNESS,ROUNDNESS AND
SQUARENESS.
• SUMMARY
• QUESTION-ANSWER
Used To Check
Minor Difference
In Learner
Measurement,to
Set
Tool,job,fixture
Etc,in Alignment
Of Machine For
Size Of Machine,
for Size Of
Finished Product
To Check Contour
Of The Surface Etc.
CONSTRUCTION OF DIAL INDICATOR
1. Bezel And Bezel Clamp:
Bezel is a part which can be rotated by hand to set zero
reading of the pointer.
2. Contact point:
contact point is provided to have contact with surface of
the job to be measured.
Made out of hardened steel and it is replaced when its
shape is distorted of worn-out.
3. Steam:
it is a tube like part used to facilitate straight movement
of plunger.
Cont..
4. Plunger :
plunger is having contact point at its end.
It is used to transmit the movement of contact point
up to the dial indicator through mechanism.
5. Back-Lug :
it is used to set dial indicator on stand.
6. Mechanism:
To transmit linear movement of plunger into circular
movement of pointer a mechanism is provided
containing gear train and lever.
WORKING
• It Is A Clock Shape Measuring Instrument Having
Circular Or Semi Circular Scale On Dial And Plunger.
• When Plunger Comes In Contact With Job Its
Movement Is Reflected By Pointer On The Dial.
• A Special Mechanism Is There To Transmit Plunger
Movement To The Pointer.
• LEAST COUNT: 0.01 TO 0.001 mm
APPLICATIONS OF THE DIAL INDICATOR
• TO CHECK WHETHER TWO SURFACES OF
THE JOB ARE PARELLEL/PERPENDICULAR
TO EACH OTHER.
• TO CHECK ROUNDNESS OF CYLINDRICAL
JOB.
• TO SET JOB ON THE MACHINE.
• TO SET FIXTURE,TOOL,WORK-HOLDING
DEVICE ETC.
• FOR MACHINE TOOLS ALIGNMENT.
• AS A MECHANICAL COMPARATOR.
• FOR DIRECT MEASUREMENT OF THIN
METALLIC FOIL,DIAMETER OF WIRE.
STRAIGHTNESS
 Definition:
• Linear Uniformity Of a work Surface Measured From
an External Reference Line Is Called Straightness.
FLATNESS
 Definition:
• Flatness is defined as the minimum distance between two
parallel planes which cover all the irregularities of the
surface under examination.
SQUARENESS
 Definition:
• Two planes, two straight lines or a straight line and a plane
are said to be perpendicular when the error of parallelism in
relation to a standard square does not exceed a given value.
ROUNDNESS
 Definition:
• Roundness is defined as the radial uniformity of the
surface of the circular part from its central line.
TESTING METHODS
STRAIGHTNESS TESTING
• Following different methods are in use for
measuring and checking straightness.
“WAPSLF”
a) Wedge Method
b) Straight-edge Method
c) Light-gap and filler gauge Method
d) Autocollimators Method
e) Precision Level Method.
WEDGE METHOD