Grizzly G4791 Owner's Manual page 51

Follow these rules and refer to the chart in
Figure 63 when using the thread dial:
Note: The thread pitch of the longitudinal
leadscrew is 8.
Thread Pitch
Figure 63.
Figure 64
Thread Dial Setting
Figure 64.
Note: The thread dial is not used when cutting
metric threads. Once the half-nut is engaged,
you must leave it engaged until the threads are
complete.