FRITSCH PULVERISETTE 7 classic line - Manual (Page 30)

Exception: Tungsten carbide balls (<20 mm) may be temporarily (a few
minutes) combined with grinding bowls made of tempered steel.
6.1.1 Size of the grinding balls
Type of feed material Suitable ball diameter
Hard sample material with a maximum feed size of 2 - 5
mm
15 mm
Fine material 0.5 mm 10 mm / 5 mm
Homogenisation of dry or liquid samples 10 mm
These are reference values: The size of bowls and grinding balls may
need to be determined through experimentation.
NOTICE!
It is not advisable to mix balls of different diameters. (If
balls with different diameters are used, increased wear to
the balls is to be expected.)
6.1.2 Number of balls per grinding bowl (independent of the material quantity)
A higher number of balls will reduce the grinding time and the grinding
result will have a smaller particle size distribution.
Ball diameter (mm) Grinding bowl volume (ml) 12 45
5 Number of balls (pcs) 50 180-200
10 Number of balls (pcs) 6-8 18-20
15 Number of balls (pcs) - 7
These are reference figures: The number of balls may need to be deter-
mined through experimentation.
Grinding balls ≤ 3 mm: Recommended ball mass per grinding bowl in grams
Grinding bowl /
Useful capacity (material to be
ground)
12 ml
0.5 - 5 ml 45 ml
3 - 20 ml
Material
Zirconium oxide 20 g 70 g
Using the device
- 30 -