In a turning operation on ductile steel, it is desired to obtain an actual surface roughness of 63 µ-in with a 2/64 in nose radius tool. The ideal rou
In a turning operation on ductile steel, it is desired to obtain an actual surface roughness of 63 µ-in with a 2/64 in nose radius tool. The ideal roughness is given by Eq. (24.1) and an adjustment will have to be made using Figure 24.2 to convert the 63 µ-in actual roughness to an ideal roughness, taking into account the material and cutting speed. Disposable inserts are used at a cost of $1.75 per cutting edge (each insert costs $7.00 and there are four edges per insert). Average time to change each insert = 1.0 min. The workpiece length = 30.0 in and its diameter = 3.5 in. The machine and operator’s rate = $39.00 per hour including applicable overheads. The Taylor tool life equation for this tool and work combination is given by: vT0.23 f 0.55 = 40.75, where T = tool life, min; v = cutting speed, ft/min; and f = feed, in/rev. Solve for (a) the feed in in/rev that will achieve the desired actual finish, (b) cutting speed for minimum cost per piece at the feed determined in (a). Hint: To solve (a) and (b) requires an iterative computational procedure. Use of a spreadsheet calculator is recommended for this iterative procedure