22" travel single axis suggestions

Considering creating a special application machine that would require a single axis with 22" of travel. It will not have to carry more than 10 lbs, but needs to have less than .0005" or better .00025" deviation under the spindle through out the entire travel.

Not worried about how to drive it mechanically or electronically. Just looking for ideas on the least expensive way to build physical parts of the stage.

Ideas?

Thanks, 

Tim G

Denver, CO