These files show the insides of the gearbox from an Abene VHF-3 mill - this gearbox drives a shaft that drives the table in X,Y,and Z - reversing the motor activates the rapids, so there is an idler gear visible near the top.

If you have one of these, it's best not to take it apart - but if you must, remove the input and output shafts, then unscrew the four nuts holding the assembly together, then pull the back off - you will need to use a pry bar to press the brass gear down as you do this - that will push its bearing out of its mounting hole. 

This is very nicely made, notice all the ball bearings - all the gears ride on double pairs of needle bearings - this is fine Swiss workmanship - this particular mill was made in 1970