( Helix-mill a hole. )
( Assumes metric, XY plane, feedrate, and tool compensation are set. )

O<helix_mill> sub
  #<xcenter> = #1 ( [mm] X center         )
  #<ycenter> = #2 ( [mm] Y center         )
  #<radius>  = #3 ( [mm] Hole radius      )
  #<zstart>  = #4 ( [mm] Z start position )
  #<zend>    = #5 ( [mm] Z end position   )

  G0 X[ #<xcenter> - #<radius> ] Y#<ycenter>

  G0 Z#<zstart>
  #<znow> = #<zstart>

  ( Mill out body with several full helical turns )
  O100 while [ #<znow> GT [ #<zend> + #<_zstep> ] ]

    #<znow> = [ #<znow> - #<_zstep> ]
    G2 I#<radius> J0 Z#<znow>

  O100 endwhile

  G2 I#<radius> J0 Z#<zend>

  ( Flat out the bottom )
  G2 I#<radius> J0

O<helix_mill> endsub

( Mill a flat groove. )
( Assumes metric, XY plane, feedrate are set, and no tool compensation. )

O<flat_groove> sub
  #<xcenter> = #1 ( [mm] X center         )
  #<ycenter> = #2 ( [mm] Y center         )
  #<sradius> = #3 ( [mm] Starting radius  )
  #<eradius> = #4 ( [mm] Ending radius    )
  #<zpos>    = #5 ( [mm] Z position       )

  #<step> = [ #5410 / 2 ]

  ( Mill out body with several full helical turns )
  O100 if [ #<sradius> GT #<eradius> ]
	  #<rnow> = [ #<sradius> - #<step> ]

	  G0 X[ #<xcenter> - #<rnow> ] Y#<ycenter>
	  G1 Z#<zpos>

	  O110 while [ #<rnow> GT [ #<eradius> + #<step> ] ]
	    G1 X[ #<xcenter> - #<rnow> ]
	    G2 I#<rnow> J0
	    #<rnow> = [ #<rnow> - #<step> ]
	  O110 endwhile

	  G1 X[ #<xcenter> - [ #<eradius> + #<step> ] ]
	  G2 I[ #<eradius> + #<step> ] J0
  O100 else
  O100 endif

O<flat_groove> endsub

( --- BEGIN CONFIGURATION --- )

( 1.6mm cylindrical cutter )
T60 M6 S8000 F200

#<_zsafe>       = 10. ( Safe Z               [mm] )
#<_zstep>       = 1.  ( Pocketing Z step     [mm] )
#<_thickness>   = 3.  ( Acrylic thickness    [mm] )

( --- END CONFIGURATION --- )

( Metric, Absolute, XY plane )
G21 G90 G17

( Spindle on, Coolant on )
M3 M8

( Dwell for 2s )
G4 P2

G0 Z#<_zsafe>
G0 X0 Y0

O<flat_groove> call [0.] [0.] [46. / 2] [40. / 2] [-1.]
G0 Z#<_zsafe>

G41
O<helix_mill> call [0.] [0.] [8.0 / 2 - #5410] [0.] [-#<_thickness>]
G40
G0 Z#<_zsafe>

G42
O<helix_mill> call [0.] [0.] [60. / 2 + #5410] [0.] [-#<_thickness>]

G0 Z#<_zsafe>

M2