beginner lathe conversion .
Not a specific recommendation, as it isn't one I have used, but www.tldp.org/LDP/Bash-Beginners-Guide/html/ looks OK.
For linuxCNC what I think of as the "command line" is the halcmd prompt that you get by running "halrun". That lets you enter all the usual HAL commands. I do a lot of my debugging that way as you don't need a complete system and it is easier to see what is going wrong.
I think that is why the latest version appears on Debian too. I haven't tried it yet, but I do have a machine running LinuxCNC on Lubuntu.
I have seen others say that ubuntu is too bloated to be teamed with LCNC . My question is why can't it be stripped of all programs that is not essential to only bare bones OS plus internet and CNC .
One very easy way is to use step-dir interface servo drives. In that case the step-dir interface is just being used as a command link to the drive.
Sorry another question can I buy a controller that will drive not only steppers but servos as well , save me from buying another board later possibly
It is relatively easy to swap interface modules with the Mesa cards too.
I think that the Pico products are a bit more fixed in their application, ie you either have a PPMC for servos or a USC for steppers, but I might be wrong in that.
The spindle motor is controlled with a vfd also has an ABZ quadrature encoder and the braking function is done with air driven by a solenoid valve.
Is enough the ac motor + vfd + encoder + brake to do precision indexing or must install a servo motor with brake ?
That would depend on your definition of "precision", the number of encoder counts and the nature of the VFD.
I have tried this without the brake, with a 100-count encoder and (very importantly) a rather old, dumb, VFD which gives zero output below 50rpm demand.
This is the link (i prefer not to embed)
That is about as bad a combination as possible, so yours would almost certainly work better.
I would suggest trying it, and if you can't get the result you want look into ways to clutch-in a small stepper motor for spindle indexing work. (using the existing brake)