Ruthless I've got such a setup and while it works I would recommend a bit more attention to detail on the installation. My system uses pressure fed pinions using a gas cylinder to load the pinion into the rack. Over time this accelerates wear and I've had to replace both the pinions [a few times] and the rack [once]. Better would be to use your rail to temporarily mount your spindle and machine an aluminum surface to mount the rack to. Then using an adustable but LOCKABLE motor mount such that while the pinion is in contact w/ the rack and there is no lash, the pinion is not 'floating' or forced into the rack. This will give you the ability to control wear a bit better and give longer life to your system. I've got a machine that is set up this way and I've yet to replace the rack or pinion [however after 4+ yrs of cutting 8-15hrs /day its now getting time to replace the pinions].
The other option is a NEXEN rack system but thats a bit more money again..
Fwiw
JFG
JerryFlyGuy
The more I know... the more I realize I don't
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)