Title: CircularityRoundness
1Circularity/Roundness
2Measurement of Form
3Geometric characteristic symbols
4Circularity Tolerance applied to a cylindrical
feature
5Circularity Tolerance applied to a sphere
6Cylindrical Tolerance directed to either view
7Characteristic irregularities of basically Round
forms - 1
8Characteristic irregularities of basically Round
forms - 1
9Characteristic irregularities of basically Round
forms - 2
10Characteristic irregularities of basically Round
forms - 2
11Application examples of Engineering parts with
functional need for roundness - 1
12Application examples of Engineering parts with
functional need for roundness - 1
13Circularity/Roundness
- Measurement Techniques
- Filtering and Reference circles
- Numerical Evaluation
- Error Correction
14Measurement Techniques
- Intrinsic Datum Methods
- Use part surface as a datum
- Extrinsic Datum Methods
- External datum such as a precision spindle
15Intrinsic Datum Methods
- Diametral measurement
- V block
- Bench center
16Diametral Methods
Dowel pin three lobed characteristic
D1D2D3D4
Dowel pin with three lobes out-of-roundness
characteristic
Elliptical part
17V Block Methods
18Fixed and Adjustable V - blocks
108o V block
60o V block
Adjustable V block
128o 34 V block
19Conversion Factors for Roundness Measurements
using V blocks
A180 - (360/n)
A included angle of the V block n number
of lobes
20Bench Center
21Extrinsic Datum Methods
- External datum Precision spindle
- Part on a precision spindle
- Probe on a precision spindle
22Precision spindle instruments
23Stylus Shape and Material
24Sharp and Blunt Stylus
25Effect of Stylus
26Suppressed Zero
27Magnification
28Effect of imperfect centers
29Effect of Combined Eccentricity and Zero
Suppression
30Filters
31Effect of filters
32Polar profiles at various filter values
33Reference criteria
Minimum Radial Separation
Least Squares Circle
Maximum Inscribed Circle
Minimum Circumscribed Circle
34Eccentric Circle
35Equation of Eccentric Circle
If E ltlt R, ignoring the higher order terms, we get
36Equation (Contd.)
(Suppressed radius)
where
37Limacon of Pascal
38Determination of Least Squares Center and Circle
39Determination of Least Squares Center and Circle
The distances a and b of the least squares center
from the center of the paper are calculated from
the following formula
Alternate Formula
The radius R of the least squares circle
40A sample uncertainty Budget for the Measurement
of Roundness
41Uncertainty Budget for the Measurement of Ball
Roundness at NIST
Using k2 we have U0.016 mm