Hi,

When you look at end milling tools, the Corner radius of the tool ist of great importance. The radius must be big enough to ensure the stability of the Corner edge, when you are ramping in. Otherwise you will get massive wear at the corner of the end mill soon. Also it is important that your end mill has cutting edges which go over the center of the mill if you want to ramp in with a high angle to ensure that chips are transported away from the Center. I use ramp angles of about 10° with a 12mm Carbide mill using Corner radius of about 5 mm and fz=0,11 when machining C45 steel. Limit is somehow at 15° but it's difficult to calculate for different mills.