${\alpha }_n$	Chisel edge normal rake angle
${\beta }_o$	Clearance angle
$C_1$	Constant dependent on drill geometry & machining conditions
$C_2$	Integration constant
$\psi$	Chisel edge angle
$f_{rev}$	Feed rate in mm/rev
$f_s$	Feed rate in mm/sec
$i$	Inclination angle
$k$	(Point angle)/2
$K_n$	Norma specific cutting pressure
${\tau }_y$	Yield shear stress
$r$	Radial distance along cutting lips of the drill
$r_p$	Pilot hole radius
$\rho$	Normalized radial coordinate
$R$	Drill radius
$R_a$	Indentation zone radius
$t$	time
$t_c$	Uncut chip thickness
$F_{cl}$	Cutting lips force
$F_{ind}$	Indentation zone force
$V_c$	Cutting velocity
$w$	(Web thickness)/2
g (${\epsilon }^p$)	Strain hardening function
θ(T)	Thermal softening function
τ ($\dot{\epsilon }$)	Rate sensitivity function
σo	Initial yield stress is, is referred as
${\epsilon }^p$	Plastic strain
${\epsilon }_o^p$	Reference plastic strain
1/ n	Strain hardening power
T	Temperature during the test
Tm	Melting temperature
Tcut	Cut-off temperature
$\dot{\epsilon }$	Plastic strain rate
${\dot{\epsilon }}_o$	Reference plastic strain rate
m 1	Strain rate sensitivity
Fs	Sliding force
μ	Coefficient of friction
σn	Normal force
D	Damage function