I've now solved my own problem with the MILL55 and WinNC / FANUC 0M using the PC keyboard for incremental jog....
1) Select jog mode, F1, F6. Jog mode is confirmed……
2) Press F1 to bring up the ‘F1 menu’. We’re still in JOG mode but notice the right chevron (>) to the right of the menu bar.
3) Select the right chevron (>) to the right of the menu bar with the mouse to display the incremental jog selections. I haven’t yet discovered how to select the chevron with the keyboard.
4) Select the desired increment. The mode changes from JOG to STEP
5) As far as I am able to determine, the jog increment is not displayed, however the incremental jog does now work using the standard jog keys on the number keypad.
6) It’s useful to be able to see the actual jogging process and actual position changes so…..Press F12 to bring up the position menu. Note, we’re still in STEP mode.
7) Select F3 to display position information.
The jog keys work in incremental mode as expected – this has been confirmed with a dial indicator placed against the bed.