- For gripping a workpiece by its inner diameter. Machine these arbors to hold a specific part. For use on lathes, milling machines, grinders, chucks, collets, fixtures, etc. How to Use: Chuck arbor in machine to be used. Tighten expanding screw so that arbor expands .005. Machine arbor to length and size required. Loosen expanding screw. Position part on arbor and tighten expanding screw.