small servos 60-110mm spin 3000-2500 and the bigger you go the slower they get, you'd have to compute how much torque you need to spin 20 lbs at 3000 rpm plus machining load and then you can go and search for a servo, at this high speed though the torque gets really small. Also the pieces diameter matters too because you wanna know how much N is at the circumference, servos specs are in Nm so you have to convert it.
are you sure you need 3000? the range on mill turns is usually around 300-800RPM and they do just fine.
Since you already have a motor I'd make a good stiff housing for the components and then just see how far you can go with what you have. You can make it future proof as well so that you only have to upgrade the servo when needed.