(info: helix: in/out cutting, cw/ccw dir with radius comp, D-holes)
o<helix> sub

#<toolno>     =  #1 (=1)
#<rpm>        =  #2 (=2000)
#<feedrate>   =  #3 (=10)
#<dir>        =  #4 (=3 2:cw, 3:ccw)
#<inside>     =  #5 (=1 1:in, 0:out)
#<cutdepth>   =  #6 (z cutdepth)
#<zincr>      =  #7 (z increment)
#<zsafe>      =  #8 (=0.5)
#<x>          =  #9 (x center)
#<y>          = #10 (y center)
#<hdiam>      = #11 (diameter)
#<faceangle>  = #12 (=0 face angle)
#<d_angle>    = #13 (=0 d angle)
#<zstart>     = #14 (=0)
#<spin_notify>= #15 (=0)
#<use_g43>    = #16 (=1)
#<h_for_g43>  = #17 (=0)
#<verbose>    = #18 (=0)

o<loadtool> call [#<toolno>][#<use_g43>][#<h_for_g43>][#<verbose>]
#<tooldiam>   =  [#5410 + .001]

         #<hr>       = [#<hdiam>/2]
         #<cutdepth> = [-1 * #<cutdepth>]
o<l00>   if [#<cutdepth> GT 0.0]
           (debug, helix: bad cutdepth #<cutdepth> - EXITING)
           (print, helix: bad cutdepth #<cutdepth> - EXITING)
           (AXIS,notify, helix: bad cutdepth - EXITING)
           m2
o<l00>   endif

         #<zincr> = [-1 * #<zincr>]
o<l01>   if [#<zincr> GT 0.0]
           (debug, helix: bad zincr #<zincr> - EXITING)
           (print, helix: bad zincr #<zincr> - EXITING)
           (AXIS,notify, helix: bad zincr - EXITING)
           m2
o<l01>   endif
o<l02>   if [[#<inside> NE 0] AND [#<inside> NE 1]]
           (debug, helix: bad inside specifier #<inside> - EXITING)
           (print, helix: bad inside specifier #<inside> - EXITING)
           (AXIS,notify, helix: bad inside specifier - EXITING)
           m2
o<l02>   endif
o<l03>   if [[#<dir> NE 2] AND [#<dir> NE 3]]
           (debug, helix: bad dir specifier #<dir> - EXITING)
           (print, helix: bad dir specifier #<dir> - EXITING)
           (AXIS,notify, helix: bad dir specifier - EXITING)
           m2
o<l03>   endif

         #<rtool> = [#<tooldiam> / 2.0]
         G40 (cutter radius compensation off)
         s#<rpm> m3 (spindle cw)
o<if1>   if [#<spin_notify> GT 0]
o<spin>    call [#<rpm>]
o<if1>   endif
         f #<feedrate>

         #<delta> = #<d_angle>
         #<d2>    = [#<d_angle>/2]

         (to avoid gouging, start point is arc opposite flat)
         (start point x0,y0 and vector to center vx0,vy0)
         #<x0>  = [#<x> + #<hr> * cos[#<faceangle> + 180]]
         #<y0>  = [#<y> + #<hr> * sin[#<faceangle> + 180]]
         #<vx0> =        [#<hr> * cos[#<faceangle>]]
         #<vy0> =        [#<hr> * sin[#<faceangle>]]

o<entry> call [#<inside>][#<dir>][#<tooldiam>][#<x0>][#<y0>][#<x>][#<y>]
         #<prex> = #<_entry:prex> (pre entry point)
         #<prey> = #<_entry:prey>
         #<vxe>  = #<_entry:vx>   (vector to arc center)
         #<vye>  = #<_entry:vy>

         (points at the ends of the arc)
         (x1,y1 start point of flat, vx1,vy1 vector to center)
         (x2,y2 start point of flat, vx2,vy2 vector to center)
o<l08>   if [#<dir> eq 2] (cw)
           #<x1>  = [#<x> + #<hr> * cos[#<faceangle> + #<d2>]]
           #<y1>  = [#<y> + #<hr> * sin[#<faceangle> + #<d2>]]
           #<vx1> =        [#<hr> * cos[#<faceangle> + #<d2> + 180]]
           #<vy1> =        [#<hr> * sin[#<faceangle> + #<d2> + 180]]

           #<x2>  = [#<x> + #<hr> * cos[#<faceangle> - #<d2>]]
           #<y2>  = [#<y> + #<hr> * sin[#<faceangle> - #<d2>]]
           #<vx2> =        [#<hr> * cos[#<faceangle> - #<d2> + 180]]
           #<vy2> =        [#<hr> * sin[#<faceangle> - #<d2> + 180]]
o<l08>   else
           #<x2>  = [#<x> + #<hr> * cos[#<faceangle> + #<d2>]]
           #<y2>  = [#<y> + #<hr> * sin[#<faceangle> + #<d2>]]
           #<vx2> =        [#<hr> * cos[#<faceangle> + #<d2> + 180]]
           #<vy2> =        [#<hr> * sin[#<faceangle> + #<d2> + 180]]

           #<x1>  = [#<x> + #<hr> * cos[#<faceangle> - #<d2>]]
           #<y1>  = [#<y> + #<hr> * sin[#<faceangle> - #<d2>]]
           #<vx1> =        [#<hr> * cos[#<faceangle> - #<d2> + 180]]
           #<vy1> =        [#<hr> * sin[#<faceangle> - #<d2> + 180]]
o<l08>   endif

         g0 z #<zsafe>

o<l10>   if [#<inside> NE 0] (inside)
o<l20>     if [#<dir> eq 2] (cw)
             (debug conventional CW,INSIDE)
             g0  x#<prex> y#<prey> z #<zsafe>
/            g42 (cutter radius comp right of path)
             g2  x#<x0> y#<y0> i#<vxe> j#<vye>
o<l20>     else (ccw)
             (debug climb CCW,INSIDE)
             g0  x#<prex> y#<prey> z #<zsafe>
/            g41 (cutter radius comp left of path)
             g3  x#<x0> y#<y0> i#<vxe> j#<vye>
o<l20>     endif

o<l10>   else (outside)
o<l30>     if [#<dir> eq 2] (2 ==> cw)
             (debug,climb CW,OUTSIDE)
             g0  x#<prex> y#<prey> z #<zsafe>
/            g41 (cutter radius comp left of path)
             g3  x#<x0> y#<y0> i#<vxe> j#<vye>
o<l30>     else (3 ==> ccw)
             (debug conventional CCW,OUTSIDE)
             g0  x#<prex> y#<prey> z #<zsafe>
/            g42 (cutter radius comp right of path)
             g2  x#<x0> y#<y0> i#<vxe> j#<vye>
o<l30>      endif
o<l10>   endif
         (entry complete: #<x0>,#<y0>,#<zsafe>)

         g0 z [#<zstart>  + 0.05] (hardcoded delta)
         g1 z #<zstart> (plunge)
         #<zcurrent> = #<zstart>
         #<_:pass>     = 1 (colon makes hidden global var)
o<l30>   while [#<zcurrent> GT #<cutdepth>]
           #<zcurrent> = [#<zcurrent> + #<zincr>]
o<l32>     if [#<zcurrent> LT #<cutdepth>]
             #<zcurrent> = #<cutdepth>
o<l32>     endif
           g#<dir> x#<x1> y#<y1> i#<vx0> j#<vy0> z#<zcurrent>
           g1      x#<x2> y#<y2>
           g#<dir> x#<x0> y#<y0> i#<vx2> j#<vy2> z#<zcurrent>
           #<_:pass> = [#<_:pass> + 1]
o<l30>   endwhile
         (final traverse at full depth)
         g#<dir> x#<x1> y#<y1> i#<vx0> j#<vy0> z#<zcurrent>
         g1      x#<x2> y#<y2>
         g#<dir> x#<x0> y#<y0> i#<vx2> j#<vy2> z#<zcurrent>
         g0      z#<zsafe>
         g40
o<helix> endsub