What tool do I use to do this?

[zaebis]

Vertical CNC Mill. Cylindrical stock in a vise facing up. Need to groove it about 0.25deep all around from outside for 2' down !! Yeah I know "just do it on a lathe...". Tell me how to do it on a mill instead !!!

I was thinking a shell mill but they are huge and big diameter. I may run out of Y travel interpolating.

[beege]

Many passes with key cutter, rough and finish?

[Glacern]

How is the groove far from the top of the cylinder?

A custom ground endmill with the shank reduced for clearance and proper flute height may do the trick.

[Geof]

Originally Posted by zaebis ..... groove it about 0.25deep all around from outside for 2' down !!

2' ???? Two Feet???? 24 inches???? Standing up?

You will need 48 inches of Z travel; that is a humongous vertical machine.

[will gilmore]

this is changing your set up but how about setting it up horizontally in a 4th axis on the mill

[zaebis]

oops sorry that was 2 inches down Z not feet of course. Ok looks like T-Slot cutter would be my first tool to try. Those are relatively cheap (HSS) and easy to come by.

Custom ground may work too but I would hate to destroy a perfectly normal end mill just for that.

[MattTheNoob]

How about a slitting saw. It'll give you more diameter to work with to keep your spindle clear of the work. Just a thought.

[zaebis]

Originally Posted by MattTheNoob How about a slitting saw. It'll give you more diameter to work with to keep your spindle clear of the work. Just a thought.

those are too thin, too many circles to do.

[PixMan]

Got budget? If you want to get the job DONE, a Valenite VS2C 4250 5B125 cutter would get through that like crap through a goose. It's a 4" diameter insert-type slotting saw with a 1.25" bore though, so may eat up your Y-axis travel as well as your budget for tooling. You'd need a 1.25" stub arbore if you don;t have one, plus the pack of ten inserts needed to load it.

Oops, I just noticed you didn't state what the width of the groove is. That cutter is a staggered tooth side-cutting style, and only one smaller at .188" width. For more flexibility and lower cost, go with their V350 line. They're available as small as 3" diameter, but take cheaper, more common VSG-style lathe inserts, so you have choices of grades, chipbreakers, shapes and widths.

I'm looking in their Milling (2007) catalog and just spotted a bargain tool. The VGM150 NG2 100W cutter is a 1" Weldon shank 3-insert T-slot cutter that has a cutting diamter of 1.5", and takes a choice of two width inserts: .093" and .125". That one would be pretty affordable, but nowhere near a HSS T-slot cutter. You can see that if you go to Valenite.com and dowload the Milling Catalog 2007, look for page B11 (not page 11 of the PDF file.) It'll certainly reach the depth, has 3 cutting edges per insert (TGEB3.52 NGM L094 or L125, both grade 5045 only.)