All,

I am cutting Cumaru which is a hard exotic almost as hard as Ipe. Cutting on a CNC at a feed rate of 60 IPM with a cut depth of 0.1”. Using an Amana 1/4” down cut spiral bit with the spektra coating. Here is my problem: they break. I have about a 50% failure rate. In contrast, I cut use a standard Bosch 1/4” down cut spiral bit all day long on the same tool path without breakage. It just gets dull quicker. I have about come to the conclusion to use the cheaper bits and change them out more often. What am I missing here? Amana tech support says to go slower. Does not make sense when I can run the Bosch at the same feed rate and cut depth. Granted, the Cumaru is hard, but the 60 IPM seems conservative? Work piece is secure and bit is tight in the spindle collet. 18,000 RPM in both cases.

insight welcomed