Careful folks: If just enough is just right, then is too much even better?
A BXA works fine on most modern 14” machines with 3/8, ½ and 5/8” tools. With some 13” machines, a 5/8” tool and BXA holders cannot be set low enough to function. ½” tools will just about bottom-out the holder. With a CXA on a 13” machine, you might be fairly close to limiting yourself to 3/8 tools or worse yet, need to trim down your ½ or 5/8 tools. I often do machining at friend’s shop on a 16x60 lathe and a CXA fits comfortably. I personally think CXA is way over-kill for a 13” machine. I keep envisioning my 325lb uncle who drove around in a 1968 VW beetle. It literally leaned to the driver side as it went down the road.
Another issue with large QCTPs on smaller machines, is that the drop-down projection of cutter position is very close (or possibly over-hanging) the left-most edge of the carriage. This can cause really nasty cases of chatter –even when taking light cuts. Ideally, the cutting action should take place as close to the center of the carriage as possible. This puts all the forces straight downward on the carriage. With all the forces happening on the left side, the right side lifts up, leading to a chatter condition. Been there, done that –and scratched my head a good long while to solve that mystery.
Finally, a really large QCTP can create impossibly tight quarters when using the tailstock with a live center. Most live centers are about 2.25” diameter. You will not be able to get your cutter close to the workpiece because the QCTP body will hit the body of the live center. Since you'll be limited to smaller size tooling, you now just shot yourself in the foot.
Summary: 13” machine + CXA is WAY too big.
Ray