Hi Folks,

I'm looking to gather some opinions about a CNC conversion I'm considering - I've recently ordered and received a rather nice Harbor Freight mill (Milling / Drilling Machine - 1-1/2 HP). It's actually quite a dandy for the price and I'm seriously considering what it would take to get some stepper based control on it. For the sake of a starting point, here's what I've compiled thus far and where my thoughts are headed - any feedback or direction would be greatly appreciated (I'll be sure to post the results of the build when completed if I do elect to go this path).

Thus far, based on quite a lot of reading, a self-imposed budget constraint and pouring through some technical information I've located the following stepper motor package. (Free SHIP to US 3Axis Nema34 Stepper Motor 880oz in Dual Shaft Control CNC Mill | eBay). 256 microsteps should yield 51,200 steps per revolution, which is quite decent resolution (although I have read the feedrate can suffer, this is acceptable for my application).

My Concerns and areas I could use some guidance:

1. Mechanically, does anybody have any experience with this mill or any like it? Should I expect to have significant tolerance issues with screw backlash or general play in the table without upgrading to ballscrews? The lead screws are 10 TPI.

2. My experience with CNC controls is with purely with Fanuc - servos as we all know are more capable, more accurate (semi-closed or closed loop typically) and just generally better in every way than steppers. That said, the Utopian world in which I throw Fanuc Beta motors on my mill is unfortunately not this one, my concern is the fact that the stepper system will be open loop. Two parts to this one - is there any reason I shouldn't be concerned with this and if I should be, does anybody have any thoughts as to how I could upgrade stepper motors to semi-closed feedback? (I intend to be controlling the mill with Mach3).

Anyway, I really appreciate the feedback folks - thanks for your time!