Small Live center

[Toolmaker51]

That ball is a better thrust bearing than many; of washer or bearing type. Near zero friction, and if carefully set, near zero endplay. I've built firearm cleaning rods with exactly same arrangement, but the bearings are spaced apart within the length of the handle. Spacing improves axial alignment. The rods are 01 tool steel, hardened and polished in contact the ball. Couple drops of gun oil and ready to go. Smoothness helps cleaning process, as fouling can be detected by feel.