When finishing high-speed milling of hardened die steel, one of the main factors to be observed is shallow cutting. The depth of cut should not exceed 0.2/0.2mm (ap/ae: axial depth of cut / radial depth of cut). This is to avoid excessive bending of the tool holder/cutting tool and to maintain a small tolerance and high precision of the machined tool.
It is also important to choose a very rigid clamping system and tool. When using solid carbide tools, it is important to use tools with the largest core diameter (maximum flexural rigidity). A rule of thumb is that if the diameter of the tool is increased by 20%, for example from 10mm to 12mm, the bending of the tool will be reduced by 50%.
It can also be said that if the tool overhang/extension is shortened by 20%, the bending of the tool will be reduced by 50%. Large diameter and tapered shanks further increase stiffness. When using a ball end mill with indexable inserts, if the shank is made of solid carbide, the bending rigidity can be increased by 3-4 times.
When finishing hardened die steel with high speed milling, it is also important to choose a special geometry and grade. It is also important to choose a coating with a high heat hardness like TiAlN.