What's needed to "retrofit" ? -want C-axis on basic CNC lathe (boxford 280 tcl)

Hey
I've (almost) bought an old boxford 280 TCL, CNC Lathe

it only has Z- and X-axis, but I want C-axis as well... will it be a (too?) difficult task to do?

- also it's a reeeeeeally old school controlling;

it has feed/ rapid overide and jog keys on the machine itself
but all other functions, you control it on the connected PC (very OLD dos system) and the basic keyboard.

to sum up:

- is it possible/ worth it to build/ retfrofit C-axis on it; what's needed to be done?
- what do I need to do to get a more "up to date" controlling for it (it really dosen't matter that it's controlled through a connected PC, but want a more FANUC-like or just a "mordern" system"


- Hope you can help me/ tell me something about it and that it isn't too stupid questions :b

Not easy to answer See what i have done
http://www.tkamsker.at:8080/web/pub/...-10b-cnc-umbau

There are a couple of ways of doing it, one is to make the spindle control as per a servo, but if you already have a non-servo capable spindle, then it is usual to place a servo motor on the final spindle shaft and implement this as the C axis.
Also servo'ing the spindle motor itself can lead to accuracy problems if a gear box etc is present.
Al.

so... i could place a servo with a belt drive directly to the final spindle shaft and control that as a C axis?

-if so... can the spindle then still run at full capacity (rpm) when not using C without damaging the C-axis-servo and without disconnecting the belt drive?

-if this is possible that sounds like the easiest/ simplest way?

You could use a way of disconnecting the motor electrically, although if you turn the C axis drive enable off, the generated voltage from the motor should not be a problem, this is the way that some of the industrial systems do it.
Al.

thanks for your (very helpful) reply, i think that's the way i'll go with :)... i'll return when the project's in progress :)