The motor shaft is 24mm.
The PCNC1100 has a high and low speed range so there is a pulley pair on the motor shaft and a corresponding pair on the spindle.
The OD of the pair on the spindle are: high range - 118mmm and low range - 172mm, the coresponding ID's are OD minus 18mm.
Access to the motor pulleys is not possible without disassembly, however you should be able to estimate the motor pulley sizes from the following:
The motor is rated at 1715 rpm at 60 hz.
With the motor running on 60.3 hz from the VFD with no load, the spindle is doing 860 rpm with the belt on the low range and 2,227 rpm with the belt on the high range.