What are the concequences of having zero nose radius and a tool with 2mm nose radius while machining mild steel with HSS tool?

Answer 1

With zero nose radius, the leading cutting corner of the HSS (high speed steel) cutting tool comes to a point. Cutting a surface with a pointy tool gives a non-smooth surface finish. Also, when cutting steel, tremendous pressures are generated at the tool tip. A tool tip that comes to a point is weak at the point and the tip can fracture easily. Unfortunately, this tool fracture makes an uncontrolled, new shape on the cutting edge that often wears really fast, and/or leaves a bad surface finish on the part. With a 2mm nose radius, instead of coming to a point, the cutting edge of the tool is rounded. One result is the same difference you would get in smoothing frosting on a cupcake with the tip of a knife (sharp tip) and smoothing the frosting with the end of a spoon (rounded tip). The rounded tip gives a far smoother surface finish. Also, instead of all of the force being pressed against a sharp tip, the 2mm radius distributes force across a wider edge, making a far stronger tool tip that won't break down nearly as readily as a sharp tip would.