Right! Try running the spindle in forward (M03) and reverse (M04). It should operate both ways from MDI commands before you try rigid tapping. You have to enter a speed command on most versions of LinuxCNC, so the MDI commands would be something like :
M03 S1500
and
M04 S1500
M04 S1500 will actually set the spindle speed to a value of -1500, what happens with this depends on your HAL config. In some systems this will generate a negative voltage to a servo drive, in others, it will activate a different relay to command the reverse rotation to the spindle drive.
Jon
