Ryobi 10" Drill Press DP102L chuck

[704311]

What size is the shaft for the chuck?

[WJA]

In my experience most of the bench top drill presses use a JT33 mount. On the larger floor models with a 5/8" capacity chuck they use the larger JT3 mount. Your chuck is probably a 1/2" capacity. We do have a article and video on how to remove and replace the chuck on a drill press. You can see it at this link How to remove and install a drill press chuck
Hope this helps.
WJA