Harig 612 - Grinding Magnetic Chucks; Grinding Wheel Mounting

Figure 13
GRINDING WHEEL MOUNTING
The grinding wheel furnished with your machine
was chosen to satisfy average shop work require-
ments. It is a balanced wheel, dressed on both sides
and cutting face. Before removing this wheel from
the grinder, dress the bottom face and grind a
piece of soft tool steel to check the machine set-up
and performance.
Use only balanced wheels to ensure getting the
maximum quality this precision machine is capable
of producing. When specific problems regarding
wheel selection are encountered, contact a grinding
wheel manufacturer or his local representative
for recommendations.
The spanner wrench (furnished) fits the wheel nut
which holds the grinding wheel on the adaptor.
Unless a right hand thread has been especially
ordered, the wheel nut has a left hand thread
(letters LH stamped on face of nut) so that the
wheel will tend to tighten under starting torque.
When changing wheel, be sure adaptor is retight-
ened. If left loose, wheel may shift and cause
chatter marks.
The socket on the spanner wrench fits the nut
holding the adaptor on the spindle. To remove
adaptor, unscrew nut completely (left hand thread)
and screw in the "puller" (furnished) until the
center screw hits the spindle end. Tighten center
screw until adaptor is free. (Fig. 13)
GRINDING MAGNETIC CHUCKS
A magnetic chuck with an untrue bottom can dis-
tort a surface grinder table to which it is clamped.
For this reason, the bottom should be wiped dry,
placed on a surface plate and checked for bow. If
the chuck rocks or pivots rather than having an
even drag, it should be placed face down on the
platen and the bottom ground flat. If a surface
plate is not available, use the grinder's platen.
(CAUTION: Never grind the platen, as this can
impair accuracy.)
Grinding the chuck surface requires special tech-
nique and great care. The "lead" filling between
the magnetic poles tends to load the wheel and will
cause the unsupported areas of the chuck over the
magnet to move with any temperature difference
created by grinding. Follow these instructions
carefully:
1. Use a relatively coarse grit wheel of medium
grade and open structure with a vitrified bond.
The 32A46-18VBE wheel furnished with the mach -
ine works well if used with a mist or wet coolant
and can be used dry if care is used to prevent heat
build- up. If difficulty is experienced, use a still
softer and more open wheel such as a 32A46-
G 12VBEP.
2. Dress wheel rather coarsely with a sharp dia-
mond . Crossfeed the diamond at a fairly rapid
rate and do not pass under wheel unless downfed
at least .0005 inches. Tighten screws holding chuck
to table with minimum force needed to keep chuck
in place. Overtightening may cause warping.
3. Chuck must be in "on position" while be-
ing ground.
4. Set depth of each cut to .0002" .
5. Turn crossfeed handwheel at least 1 /16 for each
pass, and move table rapidly while grinding.
6. Dress wheel after each cut across chuck to
remove any "lead".
7. A loaded wheel, whether caused by heavy cuts,
improper dressing or wrong type of wheel can
create heat build-up sufficient to warp center of
chuck up into the wheel and seriously affect
grinder accuracy.
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