# Lexicon

## Terms around the precision steel ball

1. Dw = nominal diameter of the ball
The diameter value used to generally designate a ball size.

2. Vdws = Variation of the ball diameter
Difference between the largest and smallest individual diameter "Dws" of a ball.

3. Ra = surface roughness
For the purposes of this standard, deviations from a geometrically perfect surface, whereby deviations in shape and waviness are not taken into account.

Note: The fixed limit values in the table refer to the arithmetic mean value of the deviation of the roughness profile from the mean line (Ra).

4. Vdwl = Variation of ball diameters in a lot Difference between largest and smallest mean ball diameter "Dwm" in a lot.

Note: The parameter applies only to balls of classes G3 to G200, except G80.

5. Vdwa = Variation of ball diameters in a grade Difference between largest and smallest mean ball diameter Dwm in a grade.

Note: The parameter is only valid for balls of classes G300 to G700 and G80.

amount in which the permissible dimension of the nominal diameter of the ball is evenly divided.

7. Dwm = mean diameter of a ball
Arithmetic mean of the largest and smallest individual diameter "Dws" of a ball.

8. DwmL = mean sphere diameter of a lot
Arithmetic mean of largest and smallest mean ball diameter "Dwm" in a lot.

9. Dws = single ball diameter
distance between two parallel planes touching the surface of a ball.

10. Lot
a certain quantity of balls manufactured under the same conditions and having largely the same properties among themselves.

11. ST = sort tolerance
Range within which "Dwml" is allowed to move within a sort.

Note: The tolerance of sorts "ST" is identical in amount to the sort-interval IG.

12. G = Class
A specific combination of dimensional tolerances, shape tolerances, surface roughness and diameter variation.

Note: Each class is identified by a number preceded by the letter "G".

13. S = selection
Distance of the mean ball diameter of a lot (for Vdwl) respectively of the subset of a lot (for Vdwa) from the nominal diameter of the ball "Dw" rounded to an integral multiple of the sort-interval IG.

14. Limiting deviation
in the sense of this standard the maximum limit deviation of the mean ball diameter, "Dwm" from the nominal diameter of the ball Dw.

15. MDW = waviness
for the purpose of this standard, random or periodic deviations of the (sphere) ball surface from the ideal spherical shape.

Note: waviness should be measured by the method of vibration velocity and subdivided into waviness bands by Fourier analysis.

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