We started making our rollers starting out with 1 inch delrin rod and using 17OD 6ID bearings. The idea was to use a 17mm bit in the tail stock to center drill the rod and then a 45 degree cutter to part it. However the 17mm bit makes the hole for the bearing a little loose. The conventional method would be to use a boring bar. However I came up with a simpler solution. I sent the tapered bit (that fits in the tail stock without needing a chuck) to a tool and die shop where they trimmed the drill bit down a little. The tool used is a holder used to make pins for pinches with a surface grinder. It has a little crank and the stock is mounted inside. the part is positioned and the crank is turned while the partt is against the grind wheel. Same way one uses to turn the ends of ball screws to fit a coupler.