What Cutter / Method ??

Yes, use a stout boring tool. Be wary of parting off dead to the length required, a facing cut will probably be needed if surface finish is important. I have a 1" 2MT shank endmill which I plunge-cut start a recess like that, then I can use a larger diameter boring tool. However, 3" dia is too big for me to part off comfortably, I would tend to saw the blanks off first and work from there.

Drill the hole from the tailstock

Once you've drilled the hole even an ordinary pointy left hand carbide tool will be sufficient for the 1/2" recess

bear in mind that you are cutting loads more material on the outer edge than the centre, and you have less torque, so cut more slowly on the outer part

edit: And practice with a few  "finishing cuts" before you reach full depth and width and have to do the real deal

Edited By Ady1 on 04/06/2013 01:42:39

The other thing to bear in mind is parting off

If you haven't done it before, as mentioned previously, you may be better sawing off 7 blanks and doing each one separately

(On a production line they would put the 3" bar through the spindle bore of a big Herbert Turret lathe to keep everything close to the chuck kinda thing)

I find that if all else fails, sacraficing a goat helps.....might only work for Myfords though?

Also bear in mind that there will be some distortion after removing such a large chunk from the middle so, assuming that it is important, allow a good few thou for final cleaning up of the two large faces.

Chris,

The tool you bored out with will clean the bottom face nicely, just do 0.005" cuts till you are happy with the finish. Make sure you have the point of the tool on the centre-line or you will leave a pip if low and chip the tool if high.

I would not attempt to part off that thickness unless you have a pretty sturdy machine. Machine the front and recess, cut off on a saw, turn around in the lathe and face the back to the thickness needed.

Trevor