
Operation
Version 1.0.2 - 2020-09-15
56
Translation of original instructions
GT25 | GT30 | GT40
EN
GT25_G
T30_G
T40_G
B_4.
fm
Grain size:
A general grain size of a grinding wheel used for surface grinding is 36 to 60. The grain indi-
cates whether a grinding wheel is coarse, medium, fine or very fine. Grain 100-180, for exam-
ple, is a fine grain. The numbers (40, 60, 80, 120) indicate the number of meshes per 25.4 mm
length of one sieve side of a vibrating sieve. The grain mixture of the abrasives is separated by
vibrating screens according to grain size.
The higher the grit number, the finer the grinding wheel.
Hardness grades:
The hardness of a grinding wheel is not the hardness of the individual abrasive grains, but the resistance of
the bond to the breaking of the abrasive grains.
With a soft grinding wheel, the abrasive particles break off the wheel slightly. In addition to the binding there is
also a fixing grinding function.
In the best case the blunting (grain breakout) and sharpening is balanced in the grinding process. This is an
important prerequisite for a better grinding effect.
Codes:
A through D: extremely soft
E to G: very smooth
Abrasive
monocrystal-
line
SA (GD)
White,
canary yel-
low
Grinding of stainless steel and high strength material.
Abrasive
monocrystal-
line
MA (GW)
Brown
Grinding of stainless steel and soft iron
Chrome abra-
sives
PA (GG)
Pink, mauve
Grinding of steel alloys, manganese steel etc., for very
smooth running
silicone car-
bide, black
C (TH)
Black
Grinding of iron, brass soft bronze etc., for soft material.
Silicone car-
bide, green
GC (TL)
Green
Grinding of hard metal, glass fibre reinforced plastic etc.,
high strength material.
Diamond
RVD, MBD
MP—SD
Grinding of hard metal, glass fibre reinforced plastic as
well as ceramic and porcelain material
Boron nitride
cubic
CBN
Dark brown
Grinding of steel alloys with chrome, tungsten, cobalt, low
wear material.
Designation
Code
Colour
Principal application
Grain size
Application area
14 - 24
Grinding steel ingots, grinding iron burrs
36 - 60
Grinding standard surfaces
60 - 100
Fine grinding and edge grinding
120 - 600
fine grinding, honing, screw grinding
Over 180
fine grinding, polishing, mirror finish grinding