Thank you Jason, good eye! I have noticed something went wrong sometimes, just never could figure where it happens. You helped me find the problem. It happens because manufacturer recommended chipload field looses its default value when you change helix angle. When you switch from say 45 deg to 30, chipload should reduce, instead it gets stuck. I will fix this as soon as possible.

Excellent, Thank you. I'd been playing with helix angle a little more & might mention that I don't think I see the problem happening when I select "Solid HP End Mill" as the Tool Type instead. As a follow up question, what exactly are the differences between the 2 tool types "Solid End Mill" & "Solid HP End Mill"? I might need to play with it more, but on the tool I'm defining now it almost seems like the default Helix Angle & Stick-Out are the only difference. If I edit those fields the "Solid HP end mill" seems to calculate the same values as the standard "Solid end mill" (or vise-versa).

Solid HP Endmill is exactly same as Solid endmill. With 2 exceptions. HP Endmill is usually a material-specific cutter that is designed to remove larger amount of material. Take deeper depth of cut etc. Also when you select HPEndmill default parameters will change, so user does not have to do this every time. But since those two are basically the same tool type, you can get same kind of results for both endmill types if their parameters match. My program looks at geometry data to determine speeds and feeds, not so much what it says in the tool type box. For example you can simulate T-slot cutter using solid endmill tool type by entering smaller shank diameter. Program will know how to adjust feedrate to compensate for reduced rigidity. Same story with extra-long endmills and even drills. Feel free to ask more questions. Bye.