ISO 32902 INTERNATIONAL STANDARD
ISO 32902:2014 STANDARD (CERAMIC BALLS: SILICON NITRIDE)
Precision grade

Variation of ball diameter (VDws)(µm) (a)

Deviation from spherical form (tDw)(µm) (a)

Surface roughness (Ra)(µm) (a)

Variation of ball lot diameter (VDwL)(µm)

Gauge interval (IG)

Description of preferred gauge

Subgauge interval

Description of subgauges (SG)


3

0.08

0.08

0.010

0.13

0.5

5/0.5.0,+0.5/+5

0.1

0.2,0.1.0.0,1.0.2

5

0.13

0.13

0.014

0.25

1

5/1.0,+1/+5

0.2

0.4,0.2.0.0,2.0.4

10

0.25

0.25

0.020

0.5

1

9/1.0,+1/+9

0.2

0.4,0.2.0.0,2.0.4

16

0.4

0.4

0.025

0.8

2

10/2.0,+2/+10

0.4

0.8,0.4.0.0,4.0.8

20

0.5

0.5

0.032

1

2

10/2.0,+2/+10

0.4

0.8,0.4.0.0,4.0.8

24

0.6

0.6

0.040

1.2

2

12/2.0,+2/+12

0.4

0.8,0.4.0.0,4.0.8

28

0.7

0.7

0.050

1.4

2

12/2.0,+2/+12

0.4

0.8,0.4.0.0,4.0.8

40

1

1

0.060

2

4

16/4.0,+4/+16

0.8

1.6,0.8.0.0,8.1.6

60

1.5

1.5

0.080

3

6

18/6.0,+6/+18

1.2

2.4,1.2.0.1,2.2.4

100

2.5

2.5

0.100

5

10

40/10.0.10/40

2.0

4,2.0.2.4

Notes


(a) The values do not take into account surface defects; hence, measurement shall be taken outside such defects.

TERMS, SYMBOLS AND DEFINITIONS
TERM

SYMBOL

DEFINITION


Surface faultiness



Element, irregularity or set of elements and irregularities of the actual surface, unintentionally or accidentaly during production, storage or surface usage. These types of elements or irregularities considerably differ from elements related to surface roughness and they should not been considered in the measurement of the surface roughness

Nominal ball diameter

Dw

Diameter value which is used for the general identification of a ball size

Single ball diameter

Dws

Distance between two parallel planes tangential to the actual surface of a ball.

Mean ball diameter

Dwm

Arithmetical mean of the largest and the smallest of the single diameters of a ball.

Variation of ball diameter

VDws

Difference between the largest and the smallest of the single diameters of a ball.

Deviation from spherical form

tDw

Greatest radial distance, in any equatorial plane, between the smallest circumscribed sphere and the greatest inscribed sphere, with their centres common to the least square sphere centre.

Ball lot



Defines quantity of balls manufactured under conditions presumed uniform and which is considered as an entity

Mean diameter of ball lot

DwmL

Arithmetical mean of the mean diameters of the largest ball and the smallest ball in a ball lot.

Variation of ball lot diameter

VDwL

Difference between the mean diameters of the largest ball and the smallest ball in a ball lot.

Ball grade

G

Specific combination of dimensional, form, surface roughness and sorting tolerances for balls. Ball grade is identified by the letter G and a number.

Ball gauge

S

Amount by which the mean diameter of a ball lot should differ from the nominal ball diameter, this amount being one of an established series. Each ball gauge is a whole multiple of the ball gauge interval established for the ball grade in question. A ball gauge, in combination with the ball grade and nominal diameter, should be considered as the most exact ball size specification to be used by a customer for ordering purposes.

Deviation of a ball lot from ball gauge

ΔS

Difference between the mean diameter of a ball lot and the sum of the nominal ball diameter and the ball gauge: ΔS=DwmL(Dw+S).

Ball subgauge:



Amount of an established series of amounts, which is the nearest to the actual deviation from the ball gauge of a ball lot. Each ball subgauge is a whole multiple of the ball subgauge interval established for the ball grade in question. The ball subgauge, in combination with the nominal ball diameter and the ball gauge, is used by ball manufacturers to denote the mean diameter of a ball lot and should not be used by customers of ordering purposes.

Hardness



Measure of resistance to penetration as determined by specific methods

Surface roughness

Ra

Surface irregularities with relatively small spacings, which usually include irregularities resulting from the method of manufacture being used and/or other influences. These irregularities are considered within the limits that are conventionally defined, e.g., whitin the limits of the sampling length.

Waviness



Surface irregularities of random of periodical deviation from the ideal spherical form. It is recommended that waviness be evaluated as velocity amplutude. In practice, the waviness components are separated from the real surface by a waviness analyser (filters).

Revision n.1