Adding a servo motor to a knee mill, worth it?

I had purchased a 4hp technics servo motor for a stepping stone project a couple years ago and it has served its purpose and now the project is getting disassembled to free up some space.

The thought ran across my mind to make an adapter plate to use it on my clone 9x42 knee mill. The mill is a j step head style. I can program the servo motor to do lots of things(max rpm, acc/dec speed, max torque ect) and currently controlling it via a simple rotary encoder for both directions.

Overall I'm happy with the mill. I don't do long run production on it. Don't mind the step head because Ive gotten pretty quick at it. Also the 3p 2hp motor on it now has always been more than enough power.

Was wondering if there is something I'm missing to make it worth changing to the servo motor.

overkill HP for table table motion drive.
Bill D

my OPINION (not knowledge) is that higher voltage is good, lower voltage means higher current, heavier gauge wire.

So I always prefer the higher voltage that I can support.
I know that doesn't mean much to many of you, but that's the way I look at it. And it's always easier to go down in voltage, but harder to go up.

If you have the gear to drive the motor , why not? Not having to change belts (most of the time) and controlled torque for tapping would be nice to have :-)

I did that on my lathe.
Going from 1.5 kW AC induction motor (220V eu) to 2.5 kW AC brushless servo at 1:3 belt drive.
HTD 8 - 30 mm wide.
I now have 90 Nm effective torque (3 secs servo overload) from 0-1000 rpm.

The end result was VASTLY better than my expectation.
Endless dramatic torque, absolutely perfect speed and finishes, and crash-stops in 0.02 seconds without damaging anything.
Steel workpieces (and the machine) will bend more than the servo pid limits fault out at.

I never ever thought more torque was needed.
I was wrong.
The current system is just outrageous and maybe 10x better.
And no belt changes, and and speed and acceleration through sw and a real-time jog knob.

An ac servo is maybe 5-7x better than a VFD/motor and 10x better than ac, industrial.

And unlike either, the ac servo cuts out before big damage when whoopsies occur.
.. or when I overloaded drilling with the TS at about 30 mm D in tool steel, around 100 rpm.
Sure, bigger proper lathes at 2000 -4500 kg mass and 25 kW motors can plow thourgh that ..
but mine is a 450 kg 12x24.
And it gets very very respectable results comparable to the Haas stuff I used to sell.

It´s unclear to me if the same benefits transfer to milling.
I suspect they do, but cannot really quantify it.

I did that on both my lathes. On the 14 1/2" South bend I added four pushbuttons like you have on radios. Each has a separate speed control so I can switch from roughing to finish to threading speeds with one finger.

You need the extra horsepower because you are slowing the motor. when it is running at half speed and rated torque, you are only getting half horsepower. I put a 5 Hp DC motor on my SB replacing the 2 Hp it came with and a 15 Hp on my formerly 5 Hp with gearbox Sheldon.

My CNC Boston mill has a variable speed spindle and I wouldn't be without it.

Bill