Most of the drill chucks I delt with used a #33 Jacobs Taper and once attached to the R-8 holder, remained there forever. The holder and chuck will come out of the spindle as a unit. Do not try to seperate them. The R-8 collets look like giant WW collets and work in a similar fashion. They are usually purchased in sets (Enco) and are not very expensive. The good news with the end mill holders is you only need a couple of the smaller sizes as the larger sizes would be used in a Bridgeport size machine.