1- Corborundum wheels:
They can be identified by their green
color. Their properties depend on
type of abrasive, grit, hardness,
structure, and binder, all of which
must be considered when deciding on
what wheel to use for a given grinding
job. Porous and soft wheels allow
of cool grinding which is gentle on
the carbide. They should be used when
grinding stress sensitive carbides.
However, soft wheels wear down quickly
and their metal removal rates are
low. Hard an dense wheels, on the
other hand, clog up easly. They increase
the rist of heatup during grinding
which may lead to the formation of
heatcracks in the carbide tip.
Tables II provide data
for correct grinding procedure and
suitable wheels. Please note that
the same grinding wheel will act harder
when running on higher and softer
when running on lowerspeed.
BÖHLER carbide tools can be ground
either with or without coolant. Successful
grinding fith coolant (wet grinding)
depends on a generous and continuous
supply of coolant. In grinding without
coolant (dry grinding) care must be
excercised to keep the grinding area
from getting unduly hot. To avoid
heat cracks, carbide inserts which
are hot from grinding must never be
quenched. Wet grinding is suitable
for jobs with high removal rates,
e.g. regrinding or reshaping of tools.
2- Diamond wheels:
Their properties depend on diamond
grade, grit, hardness, concentration
and binder, and they must also be
carefully selected to meet specific
grinding job requirements.
a) Diamond wheels with metal binder:
Distinction is made wheels with soft
(bronze) binders and wheels with hard
binders. Both types are highly wear
resistant and superior to wheels with
epoxy binders, but may quickly lose
their bite if made from medium or
fine grit. Best results are achieved
with coarse grit wheels and wet grinding.
b) Diamond wheels with epoxy binder:
These wheels are rather soft in bitewell.
They are suitable for high metal removal
rates and are preferred for precision
grinding. They are sensitive to nigh
grinding pressures and the resulting
high temperature and must be treated
carefully when used in dry grinding.
Due to their excellent bite, these
wheels may be used in some cases to
grind both shank and carbide tip in
one operation. However, their shape
retaining ability and service life
isinferior compared to wheels with
metal binder Diamond wheels with armored
grain are used mainly for pregrinding.
c) Diamond wheels with ceramic
binder;
A suitable wheel for economic machine
grinding of carbide tip and shank
in one operation. Adequate cooling
is mandatory.
d) Diamond wheels with carbide
binder:
A wheel excellent shape retaining
ability. Low grinding pressure and
sufficient cooling will reduce the
risk of the workpiece getting to not.
Clogged diamond wheels will lose their
bite. Like dull wheels, they cause
excessive heatup of the contact area
which may damage both work piece and
wheel. Dressing them with a fine grit
carborundum stone will restore their
bite. Heavily clogged, dull or unevenly
worn wheels must be resurfaced and
trued. This is normally done with
lose silicon carbide grain on a cast
iron plate. Size of grains should
always correspond to the grit of the
wheel to be resurtaced.
Brazing
Carbide Tips
