BS 6740:1987

National foreword
Committees responsible
Method
1. Scope and field of application
2. References
3. Definition
4. Instruments
Annexes
A. Departure from roundness of the measured profile of
    the workpiece
B. Procedure
C. Calibration
D. Determination of systematic errors of rotation
E. Rules for plotting and reading polar graphs
F. Determination of least squares centre and circle
Table
Limiting values of upr
Figures
1. Spherical stylus
2. Cylindrical stylus
3. Toroidal (hatchet) stylus
4. Ovoidal stylus
5. Typical transmissions showing rate of attenuation
    given by two independent C-R networks of equal
    time constant
6. Assessment of roundness from least squares centre,
    triangle Zq
7. Assessment of roundness from minimum zone centre,
    triangle Zz
8. Assessment of roundness from centre of minimum
    circumscribed circle, triangle Zc
9. Assessment of roundness from centre of maximum
    inscribed circle, triangle Zi
10. Slight increase of the radius of the eccentric
    plot in the perpendicular direction
11. Inclination of the axis of the workpiece to the
    axis of rotation
12. Choice of direction of measurement for a conical or
    toroidal workpiece
13. Ball-bearing raceway
14. Closely and widely spaced irregularities
15. Effect of stylus radius when in contact with
    surfaces
16. Traces by hatchet and sharp stylii
17. Errors in measurement resulting from variation of
    the offset
18. Dynamic calibration
19. Illustrations of spindle errors and test piece out-
    of-roundness
20. Example of spindle error and test piece error
21. Avoidance of excessive distortion due to polar
    plotting
22. Angular relationships
23. Diametral variations
24. Convex surfaces which appear concave after
    magnification
25. Determination of least squares centre and circle

Uses contact (stylus) instruments.

This International Standard specifies a method for determining departures from roundness by measuring variations in radius by means of contact (stylus) instruments.

It establishes

1. types of instruments and gener requirements;
2. recommendations for the use of instrument
3. procedures for calibration of instruments a verification of their characteristics.

This International Standard applies to the assessment of the departures from ideal roundness of a workpiece through the medium of a profile transformation, obtained under reference conditions, expressed with respect to any one of the following centres:

1. centre of the least squares circl
2. centre of the minimum zone circl
3. centre of the minimum circumscribed circl
4. centre of the maximum inscribed circl

Each of these centres may have its own particular application. The position of the least squares centre can be calculated from a simple explicit equation given in Annex F.

Departures from roundness of the measured profile, procedure, calibration and determination of systematic errors of rotation are dealt with in Annex A to Annex D, respectively. Annex E gives rules for plotting and reading polar graphs.

NOTE 1 Profile transformation is defined in ISO 6318.

NOTE 2 Reference conditions include the stylus, frequency limitations of an electric wave filter (if used), permissible eccentricity of the graphical or digital representation of the profile (generally 7 % to 15 % of its mean radius, see Annex E), the position of the measured section or sections relative to some feature of the workpiece.