Common Drilling Formulas

RPMRPM = vc x 12 3.14 x D or RPM = (3.8197 / D) x SFM

(rev/minute)

Cutting Speed

vc = RPM x 3.14 x D 12 or SFM = 0.2618 x D x RPM

(ft/min)

Feed Rate vf = IPR x RPM (inch/min)

Cross-sectionarea of hole AT = 3.14 x R

2 (in2)

Material Removal Rate Q = vf x AT (inch

3/min)

PowerRequirement

Pc = D/4 x f x vc x kc 33,000 x (Hp)

Torque Mc = Hp x 5252 RPM (ft/lbs)

Feed Force (approx.) Ff = .7 x D/2 x f x kc (lbs)

Machining Time

Tc = L + H vf or Tc (seconds) = (60 x feed minus stroke) IPM

(Min/piece)

f = Feed per revolution (IPR) (inch/rev)

h = Distance from drill point to workpiece before feeding (inch)

kc = Specific cutting force (Lbf/inch2)

L = Depth of hole (inch)

= Machine efficiency (%)

D = Tool diameter (inch)