Calculate Drilling Speed and Machining Time

Calculate the drilling speed if a 50 mm dia hole of 60 mm depth is to be drilled in a M.S. component. The feed rate is 0.2652 and MRR is 200 cm3/min. Also calculate the machining time.

Solution

Given  MRR = 200 cm³/min

= 200000 mm³/min

D = 50 mm

l = 60 mm

f = 0.2652 mm/rev

MRR = π D² f N/ 4 mm³ / min

N = 200000 × 4/ (π× (50)² × 0.2652)

= 384 rpm

V = π DN/1000

= (π × 50 × 384)/1000 = 60.3 m/min

Breakthrough distance, A = D/3.3286 = 50/ 3.3286 = 15 mm

Total length of drill travel, L = l + A + 2

                                        = 60 + 15 + 2 = 77 mm

Time for drilling hole =

            L / f N = 77/ (0.2652 × 384)

                        = 0.7561 min