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GRINDING-IN A MAGNETIC CHUCK

The first step in surface grinding is to check, and if necessary grind-in, or true, the chuck. Truing the chuck is usually not necessary unless it has been removed and reinstalled or a new chuck is being used for the first time. Any grinder chuck should be checked occasionally and, if necessary, trued by grinding a minimum amount from the chucking surface. To true a grinder chuck, the following procedure
may be used:
Step 1 Mount the chuck and align it in both table and saddle axes using a dial indicator with .0001-in. resolution.
Step 2 Use the indicator to check the chucking surface to determine if truing will be necessary.
Step 3 If so, select and mount a proper wheel for this grinding task.
A good choice would be a friable grade of aluminum oxide, 46 grit, J grade, 8 structure with a vitrified bond.
Step 4 Mark the entire surface of the chuck with pencil lines. As you are grinding, the removal of the last pencil lines will show you when the task is finished.
Step 5 True and dress the wheel. Make the final dressing pass with a relatively fast cross movement of the diamond, for a free-cutting grinding action.
Step 6 Magnetize the chuck.
Step 7 Turn on the wheel and let it run for several minutes to thermally stabilize the spindle and its bearings. Then, stop the wheel rotation.
Step 8 Bring the wheel down toward the chuck, using a feeler gage to set the wheel a few thousandths of an inch above the chucking surface. Then, restart the grinding wheel.
Set the table in motion with the table stop dogs set to overtravel about 1 in.
at each end. Lower the wheel slowly the additional amount while you are moving the table saddle back and forth crosswise until you find and barely contact the highest point on the chuck’s surface. Then, start the grinding fluid.
Step 9 Set the downfeed handwheel collar to zero.
Step 10 Using a downfeed of no more than .0002 in., a fairly rapid table speed (50 to 100 sfpm), and a crossfeed of about one fourth the wheel width on each pass, grind to a cleanup condition on the chucking surface. Remove only enough material to clean the surface completely. (The total amount is usually no more than .001 in.)
Step 11 Remove any remaining burrs with a fine-grit hand stone.

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