01 Selection of cutting groove type
When we talk about a good cutting profile, what do we mean? A cutting profile refers to a series of geometric characteristics of a cutting tool that affect tool life, chip formation and evacuation, as well as stability and safety. Essentially, a good cutting profile is a layout that allows for easy and correct chip formation.
The characteristics of the cutting edge depend primarily on the grade of carbide material used, and secondarily on the flute shape of the cutting edge. Both need to be correctly selected based on the type of operation being performed. A practical method for evaluating the flute shape is to examine chip formation during the cutting process. Ideally, the chips should not be too long or too short, and should be spiral-shaped.
Good cutting processes involve efficient chip formation and evacuation, which depends on the tool's basic fluting profile—how the cutting edge is positioned within the tool holder or end mill. Positive-angle fluting (when combined with a flat rake face) reduces cutting forces and heat generation. Unfortunately, the longer the chip, the lower the mechanical strength of the cutting edge. Negative-angle fluting provides good edge strength and produces shorter chips, but increases cutting forces and heat.
02 Three different types of slots
However, the actual cutting groove is on the cutting edge. This cutting groove consists of three parts: the cutting edge groove (edge treatment or edge preparation), the chamfering groove, and the chip breaking groove (rake face groove).
The figure shows three different types of troughs.
There are three basic types of cutting edge grooves: sharp edge, rounded edge, and chamfered edge. Sharp cutting edges can provide lower cutting forces, reduce built-up edge formation, and provide longer tool life, but their stability is inferior.
Chamfered flutes are a transitional type between cutting edge flutes and chip breaker flutes. Positive angled chamfered flutes offer lower cutting temperatures, less wear, higher cutting speeds, a smaller maximum pressure zone, and lower cutting forces. However, the cutting edge experiences higher tensile stress accumulation, and the risk of chipping increases.
The cutting edge flute shape and the chamfered flute shape together determine the tool life. To fully utilize the cutting edge flute shape and the chamfered flute shape, the feed rate needs to be greater than the dimensions of these flutes. The actual chip formation process is determined by the chip breaker flute shape.
Hard chip breaker flutes can trap chips as they form, deforming and breaking them into short, fragmented chips. A disadvantage is that the concentrated cutting forces make the cutting edge more susceptible to damage. Soft chip breaker flutes produce longer chips. This flute provides a stronger cutting edge. Medium flutes fall between the two.
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