A Definitive round column CNC thread.

[craig.evert]

I took delivery of an older Taiwanese RF30 with hardly any use on it. It is stripped down in my garage awaiting a complete rebuild. I have spent 10s of hours reading about how one should not try to make a cnc mill out of a round column machine. I have seen various solutions but have never seen any empirical results. Before I go down the rabbit hole, I would like to ask a few specific questions?.

The intent is to be able to move the head up and down like on a dovetail machine (not just the spindle) with CNC control.

Assuming one could prevent the head from rotating around the column....imagine a very rigid vertical linear rail equidistant from the centre of the column as the tool axis....since you would not be able to clamp the head to the column with the two (or three) bolts at the rear of the head, how much play would one get in the head to column journal? or rather, is that exactly the issue. In short, would my best expected result be to maintain the tramming integrity (but require the head to be locked after every move)but never be able to let the head slide freely on the column as on a dovetail?

[awerby]

I suppose you could set up some rails that prevented the head from swinging around too much - is that what you're talking about doing? Or are you also replacing the rack-and-pinion that drives the quill?

[Bubba]

I have an RF31 that I converted to cnc ~10 years ago. Yes, registration of head can be a problem IF you move it during a job. However, I have found that by careful planning and tool selection, that I don't NEED to move the head for a job. I have seen several methods over the years to keep it aligned, but again I think they are more work than its really worth.

Just my opinion.