Lecture-3 specific cutting energy

Specific energy is the amount of energy required to remove a unit volume of the work material. 

The rate of energy consumption during machining (P_m) is the product of the cutting speed (_VC)  and the cutting force (F_C). Thus, 

P_m = F_C. V_C 

Both the rate of energy consumption and the metal removal rate is proportional to the cutting speed. A parameter giving an indication of the efficiency of the process, independent of the cutting speed, is there for the energy consumed per unit volume of metal removed, referred to as be specific cutting energy (P_S). This parameter is given by 

A_O  = cross-section area of the uncut chip 

The specific cutting energy can vary considerably for a given material and is affected by changes in cutting speed, feed, tool rake, and so on. However, for a given tool rake at high cutting speeds and large feeds the specific cutting energy tends to become constant, as can be seen in figure 3.1. This constant value can be a useful guide, in practice, to the forces required to cut a given material at large speeds and feeds.