Making a half round cut in a rod

[tommyBoy]

Hi,
I am trying to create a piece of decorative hardware. I have a 5/8" diameter stainless steel rod. I want to cut a 5/8" diameter groove half way through at the end. Picture the old Lincoln Logs how they fit together at the ends to form 90 degree corners. The half cuts at the ends allowed them to stack and lock together. What's the best method and cutter to use? Do I plunge a 5/8" diameter, flat bottomed end mill down and through or do I use a rounded end mill and go through sideways? Or is there another type of cutter that would fit on a mill? What speed? What lubricant? Does SS present unique problems that I should know about? I will need to make about 20 such grooves in total. I have some self-taught experience with my Smithy lathe and mill combo, but I'm probably doing things that would make a professional machinist cringe. Dispite this, I usually manage somehow to make the machined parts I need.

[tommyBoy]

Should I have put "Need Help" instead of "Newbie"?

[beege]

Hopefully, you are going to use 303 stainless. 304 and 316 are harder to machine, because they will work harden on you. I'd use a Ø5/8" end mill, stub carbide, and come in from the side. Oil works for me. Decent cutting oil, not motor oil, not sewing machine oil. Brush it on, and make sure you aren't recutting chips.

[tommyBoy]

Thanks Beege for replying. I've had the order page for the end mills open on my computer screen waiting for a response. I wanted to get the right cutter.
I lucked out on my choice of 303. I saw all the choices and took my best guess.
Just so I am clear, the cutting action will take place on the side of the end mill, not the end. Correct? So I will need at least 5/8" cutting length. Is there a special end mill that specifically cuts like that or are all end mills designed to cut from the side as well as the end? "Stub" just means short shank? 2 flute or 4? I assume 4 makes a smoother finish?
Any recommendation on the speed for the cut?
Sorry for all the questions, I've had metalworking lathes in my shop for 15 years and made a bunch of useful things, but I just want to do it like a machinist this time instead of like a weekend warrior. Thanks for your help.