I just installed and configured a 4th axis on the mill. Everything is setup and working perfectly. I can use MDI to move the axis but I cannot figure out how to jog the axis with the keyboard. Is there a set of keys that are already configured like X, Y, and Z or do I have to manually setup the A axis with the system hot keys.

read somewhere it was - and + but that did not work.

I also tried to search "jogging A axis" but the forum won't search unless all words are more than one character so that was zero help.

Thanks in advance.

Try Page Up and Page Down.
 

Page up and down is the Z axis.

Configured the A axis in system hotkeys and it worked. Then X, Y, and Z wouldn't work so I configured all 4 axis in system hotkeys and all is good now. Before this all were 999.

BTW the A axis is now + and -

Jeesh, sure you're right.        (been a while .... sorry for the mis-info)
I saved a large file on your works. Very impressive !
I've been watching for your Allison V-1710 or Merlin build. 
Cool stuff.
Thanks,
Russ