Lexicon

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

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

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).

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.

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.

IG = grade interval
amount in which the permissible dimension of the nominal diameter of the ball is evenly divided.

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

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

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

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

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.

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".

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.

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.

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.