Turning Question

[Al_The_Man]

I am helping someone do a CNC retrofit to a Lathmaster 9x30.
We are looking at putting either an AC or DC servo as a spindle motor.
The machining question we have. Is there a real advantage to upping the Max. spindle speed on this from 2000rpm to 3k or 4k.?
Is there a real benefit as to finish or tooling for the extra SFM at these speeds?
I don't really see a problem of the spindle bearing being affected, if they are we put in higher rated ones.
Al.

[Geof]

Simple answer...yes.

SFM for steel can be up 900 for finishing with carbide and this translates into nearly 3500 rpm for 1" dia. Brass and aluminum are higher still.

Make sure the chuck is rated for the speed you install.

[Al_The_Man]

Thanks, we are looking to put CSF on it as well.
Al.

[Runner4404spd]

AL,

i'm interested in what ac or dc servo motor you plan on using. i currently have a 3HP 3phase motor on my 9x20 and i love it. i run with a vfd and it has all the torque i need at any speed range.

how big of a servo motor do you plan on using? i have been looking for a 5 HP servo motor with drive, but am having a hard time finding one. ideally i would like to set this up with an encoder so i can have an indexable head.

Jerry

[Al_The_Man]

Considering the original is fractional HP, 5HP, or even 3HP, would seem a bit overkill for that size of lathe, not to mention physical size.
I am looking at 1 ~ 2hp AC servo mainly because of top rpm, although I have a DC servo with top rpm of 4000, so I may use this, there are many SCR drives available up to 2HP DC can be had very cheap on ebay. They have tach feed back for precise control, the draw back is they are not isolated so I am looking to put together a analogue/analogue isolation circuit so I can control from a Galil card.
I will be putting an encoder on the spindle shaft for CSF and threading.
Al.