Re: [CAD_CAM_EDM_DRO] Newbie question on Ballscrews....

dspinnett@... wrote:

> Hi all.
>
> I recently bought a new 2hp Grizzly mill/drill, and would like to
> convert to ball screws in preparation to a CNC conversion
>
> 1. Could you recommend a particular style, brand and where to get?

Note that many lower-cost ballscrews are not anti-backlash, and
are made for power transmission, not precise positioning.

> 2. What kind of quality do I need to keep .001 or better in a 6" or
> so work envelope?

Well, you need anti-backlash nuts, and probably a low-precision
ground screw. You could use selected rolled screws, but you
can't guarantee .001" error over 6" with pedestrian rolled screws.
Over that distance the variation in pitch would be small, though,
so you could compensate in the software by selecting the right
number of steps/inch.

> 3. If I buy a ballscrew, what to I do with the ends where it goes
> into the blocks on the mill? Are the ends turned, or do I need to
> modify the ends somehow?

You will probably need to turn the ends down to fit whatever end
bearings you use. Generally, you would use two bearings, preferably
angular contact types, at one end, with a spacer or preloading
'thimble' that squeezes the bearings together to eliminate any
axial free play in the leadscrew. For a 6" travel, you can probably
skip the far end bearing completely. Note that these screws are
hardened, so carbide tooling is almost the only way to turn them.

Jon