circular interpolation question

I'm circular interpolating a .1615 dia. hole .400 deep in brass using a .125 end mill. Could someone look over my code. Working pretty good but having some chatter issues. Running Citizen L-20


PROCESS 11 CONTOUR_0.094)
N7
G19 G0 X0.5
Y-0.018 Z0.401
G1 X0. F6.83
G41 Z0.391 F13.65
G3 Y0. Z0.382 R0.009
Y0.036 Z0.4 R0.018
Y0. Z0.418 R0.018
Y-0.036 Z0.4 R0.018
Y0. Z0.382 R0.018
Y0.018 Z0.391 R0.009
G1 G40 Z0.401
G0 X0.5
/B9 (HIGH PRESSURE OFF)
G50 W0.59 (CANCEL OFFSETS)
M60
G0 X0.9 T0
M1

G99 G40 G18 M60 (CANCEL MILLING)
!L10