4th axis as a "poor man's lathe"

[m_c]

I would say that holding torque is better than what I'd expect to get from a 180W servo.
You could probably improve it through tuning, but 180W is never going to have lots of holding torque.

A quick search tells me a JMC 180W 3000RPM servo has 0.6Nm and 1.5Nm peak torque, so even through a 3:1 reduction, that's only 4.5Nm peak.
You can put that kind of torque through a decent screwdriver with a bit effort, so on a 4" chuck, it's not going to take much effort to move things.