Without knowing the diameter of your sterling parts, it's hard to specify spindle speeds or feed rate. As diameter increases, the spindle speed should go down, all other things being equal. What you need to control for is surface feet per minute at the tool tip to calculate feed rates. Is this a CNC lathe you're planning to use? I looked online, but couldn't find any specific recommendations for sterling silver in any of the usual tables, probably because it's not usually machined this way. But it cuts similarly to copper (difficult and gummy); any speeds and feeds that work for copper should work about the same for sterling.
If you want to save yourself some grief, turn the parts in machinable wax and have them cast in silver by a jewelry casting house. That way you'll save a lot of time you'd lose trying to recover those valuable chips from the depths of your machine...