Spindle Taper Problems
In-Place Regrinding Process
Machine Alignment &         Calibration

Before the start of the in-place spindle taper regrinding process, amount of taper runout, extent of taper contact, taper gage line dimensioning, and drawbar clamping retention must first be determined.

Pre-grinding Process:

1. Determine taper runout: A .00010" or .000050" dial test indicator reading is taken from the spindle taper surface. These readings are augmented using a precision test bar.
2. Determine taper contact: The amount of taper contact is determined using a precision taper gage with bluing. This procedure shows the extent of contact, as well as the points in the taper at which contact requires improvement.
3. Taper gage line dimensioning: The precision taper gage is also used to determine the gage line dimension.
4. Determine drawbar clamping retention: This reading can be acquired using a precision dynamometer that has been clamped into the spindle.

1. All measurements are documented and the spindle centerline is checked for purposes of grinding unit alignment.
2. Specially designed grinding equipment is put to use.
3. A series of fine tuning adjustments of the grinding unit (inside the spindle taper) are made.
4. Grinding continues until an acceptable level of taper contact has been achieved (usually no less than 90 percent contact and in most cases closer to 100 percent). At this point the spindle taper grinding process is complete.
5. All measurements documented prior to regrind are again preformed and documented.
6. After the results are reviewed by the customer and accepted, the grinding unit is disassembled from the machine.
7. The machine tool is now ready for set-up to once again run accurate precision parts.