Turning operation:

In turning operation, one must distinguish among longitudinal feed (tool travels in the direction parallel to workpiece axis), angular feed (tool travels at an angle to the workpiece axis, namely, in taper turning) and cross feed (tool travels in the direction perpendicular to the workpiece axis). Furthermore, the wished depth of cut might be set along the help of a hand wheel that can give accuracy upto 0.01 mm.

The depth of cut (d) is described as the thickness of the layer of metal eliminated in one cut (or pass), and calculated in the direction perpendicular to the machined surface. This is always perpendicular to direction of feed motion. This is evaluated as

d_l =( D_i - D_l)/2 mm     (for longitudinal turning)        ---------- (2(a ))

 d_b =( D_b - D_i )/2 mm  (for boring)      -----------(2(b))

d_f = l_i - l_f         (for facing operation)    -----------(2(c))

here, l_i is initial length of the workpiece & lf it is length after one facing pass. D_i refer initial diameter, D_l refer diameter after longitudinal turning, and D_b refer diameter after boring.

The cutting speed (also known as peripheral speed of the workpiece) throughout turning might be computed if the spindle speed (rotational speed abbreviated as N) of the workpiece and workpiece diameter (D) are known. This might be evaluated from Equation (3(a)).

V  =  (π DN) /1000   -------------- (3(a))

Here, V is equal to cutting speed in m/min, D is equal to diameter of workpiece in mm, and N is equal to RPM.

If diameter of workpiece is constant, then the value of 'V' also remains constant, else this varies say, in case taper turning and face turning (Fig 2). In case of face turning, V differs from the center of the workpiece to the outer periphery. Here, the cutting speed differs from zero at the center (D = 0) to the maximum at the outer periphery.