===== case 0000 | clear_z=25.0 clearance=40.0 compound_angle=29.5 coolant_type=1 degression=1.5 depth=0.0 exit_taper=0.0 first_depth=0.0 infeed_mode=0 insert_r=0.0 internal=True lead_in=0.0 n_passes=8 pitch=2.0 pullout_feed=0.0 rpm=400.0 spring_passes=1 taper_ends=0 thread_form=0 tool=10 x_end=27.835 x_start=27.835 z_end=-20.0 z_start=3.0 =====
!! ValueError: threading: the internal retract diameter works out at -12.165 - clearance 40.000 is bigger than the bore
===== case 0001 | clear_z=25.0 clearance=3.0 compound_angle=29.5 coolant_type=1 degression=1.5 depth=0.0 exit_taper=0.0 first_depth=0.0 infeed_mode=0 insert_r=0.0 internal=True lead_in=0.0 n_passes=8 pitch=2.0 pullout_feed=0.0 rpm=400.0 spring_passes=1 taper_ends=0 thread_form=0 tool=10 x_end=1.0 x_start=1.0 z_end=-20.0 z_start=3.0 =====
!! ValueError: threading: the internal retract diameter works out at -2.000 - clearance 3.000 is bigger than the bore
===== case 0002 | clear_z=25.0 clearance=3.0 compound_angle=29.5 coolant_type=1 degression=1.5 depth=2.1651 exit_taper=0.0 first_depth=0.0 infeed_mode=0 insert_r=0.0 internal=True lead_in=0.0 n_passes=8 pitch=2.0 pullout_feed=0.0 rpm=400.0 spring_passes=1 taper_ends=0 thread_form=0 tool=10 x_end=27.835 x_start=27.835 z_end=-20.0 z_start=3.0 =====
!! ValueError: threading: depth 2.1651 is deeper than the pitch 2.0000. Depth here is a RADIUS - 0.613 x pitch for a 60 degree thread - while a G76 K word is a diameter, so halve it
