It mainly on how much power is available and how rigid the machine is. Rule of thumb 10 to 20% of the diameter of the cutter to avoid breaking them!

BUT! 304 doesn't machine well – sticky, and it's on my Awkward List. There are so many other variables I don't think it's possible to give precise advise. Always best to take the deepest cut than can be managed because anything else blunts the cutter for little return.

So I experiment. What I usually do is start with the recommended values, and reduce them by 20 – 60% because they balance finish, tool-life and power consumption against rapid metal removal in production. This isn't necessary for hobby purposes. The cutting rates imply heavy powerful machines, and my WM18 – as milling machine go – is on the light side.

I generally increase the depth of cut and feed-rate while listening to the motor. I like to hear it working hard short of labouring and certainly don't flog it. If the job chatters or the finish is unacceptable, HSS probably needs to be backed-off a bit. (Carbide may need to be pushed harder.)

303 stainless is much more machineable.

Dave