Does a VFD do the trick?

Hello friends,
I fell over my own words yesterday and have to make the best out of it.

A (2,5-3tons) beauty of surface grinder from 1957 I have to get again to
work. Complete new electrics with a PLC.
What I thought were reduction motors are plain three fase motors (1700
revs, 125W) inside 1 to 1 geared.
Out side reduction Y 1:3 makes 1,7mm per motor turn
and Z 1:7,5 makes 0,13mm per motor turn.
With solid state relays I will get the Y movement reasonable well to work.
But for the Z movement not. I would like to have an automatic down feed
graduable from 0,001 to 0,04mm until I am close to the final measurement
and still be able to manage the machine by hand.
That makes me exclude steppers as option.

Does a VFD on standard three fase motors do the trick that I can turn it
just something like 2 degree or more per impuls and later leave it free
spinning?

As you know me, I work on all kind of machines, but I hadn´t to convert
any with this kind of task and have no hands on experience with VFD's.
The PLC has encoder inputs so if necesary I can hook some on the motors,
screw or nut.

The owner first of all needs the machine running, keeping future options
open, but a automatic use and position feed back will be greatly
apreciated. And tiny VFD's aren´t that much out of financial reach.

Who has played with VFD's and standard threefase motors (240V Delta
generated with slave motor) and can give me a reference if it is feasonable?

Best regards from Costa Rica, where clocks work diferent.

Sven Peter