Look up feed and speed calculations in your Machinery Handbook, or any online reference.
http://www.custompartnet.com/calcula...speed-and-feed
GWizard is great as well if you're looking for more data (cutter deflection, MRR, HSM calcs, etc).
You might want to jump up to a larger/carbide endmill to avoid deflection in that cut. For a 3/16" HSS end mill taking a full width slot with 1" of tool stickout, you can only take ~0.04" per pass before getting noticeable deflection.