Reverse thinking on a 4th axis

[whiteriver]

Question about VM5 and a 4th axis. I want to put a 4th axis rotary on my router but the gantry height is only 7". Can I rotate my router 90 deg and use the Y axis as the Z and use my A axis for the rotary.
Am I seeing this correct? In a normal setup If the part is rotating then the Y axis would stay put the Z would move up and down and the X would go back and forth. Would the Y need to move or would the fact that it rotates alow the bit to get to all parts.

Donny

[Hobbiest]

I don't see why not. Horizontal milling machines are oriented in this way. Wiring may have to be reversed in actual use though (unless your software can do it) to switch the X and Z, as the X will now be the axis moving the cutter to the work.