Re: [CAD_CAM_EDM_DRO] How round are your milled parts?

doug98105 wrote:

> Group,
>
> Just out of curiousity, how round will your mill cut parts?
>
> I was making some flat plates, 1/8" thick, 6061-T6 aluminum.
> Different diameters, about 6" to 8.5". Using a .010" finish pass
> with a 3/8" diameter end mill, I'm getting from .0005 to .0012" out-
> of-roundness. Well within the customers tolerance of .002"+/- on
> diameter.
>
> My curiousity is aimed more at factory made CNC's or retrofits of
> factory machines, especially newer machines. For instance, how
> accurate are the new, low cost knee mills as they come from the
> factory?

I'm doing about the same, maybe just a little bit worse, about
.0015". This is almost all backlash in the leadscrews (and a little
flex in the screws, too). It is a 55+ year old round-ram Bridgeport.

Jon