Thanks. The reason I say I'm thinking about using a 20mm dia cutter, is the doc. if I'm going 35mm in one pass, then tool deflection could be an issue ?. So I thought about using the 20mm endmill do take 95% of the material away, then go to a 10mm dia endmill to do the finishing passes at full depth. I have a 50mm shell mill. A bit nervous about doing anything else but surfacing with it.