Originally Posted by philbur  Seems like a lot of work for zero gain to me. |
Not necessarily. First, I don't believe it is a lot of work. Mounts are still needed and a coupling is still needed. When Bridgeport made their Boss 3 CNC with steppers (I have one), they had a 1:1 ratio and the motors were turned so they did not stick out - they were under the table.
Also, there are potential challenges with a direct drive and coupling arrangement. Care needs to be taken to get shafts to align and couplings can also be problematic (although with hobby machines there is far less demand on them). Plus there is the added cantilevered length to handle. The bearing consideration you mention is minor if it even exists.
Most commercial CNCs use belts. IMO, I'd rather deal with a belt than a coupling because there is more design flexibility.