As fast as you can. Since you are only cutting on about 1/8 of a revolution it's very easy to get the tool bouncing. With the balanced piece of wood on the other side I was able to turn it up to a moderate speed. My lathe doesn't have a direct read out but has a chart to give me the speeds. When I get back out to the shop I will estimate the speed I was turning and then check the numbers on the back and give you a reading. My thoughts are in the ball park of 500 to 800 rpm but I'll have to look.