; bore - helical boring subroutine. Spirals down in full-circle passes,
; then a partial-arc cleanup and a spring pass at final depth.
; Requires globals: #<_z_top>, #<_z_bot>
; Requires tool loaded (uses #5410 for diameter)
o<bore> sub
	; o<bore> call [x][y] [d] [stepdown]
	; #1=x #2=y #3=d #4=stepdown

	G90
	G91.1

	G0 X#1 Y#2
	G0 Z#<_z_top>
	G1 X[#1+#3/2-#5410/2] Y[#2]
	G17

	#<r> = [#3/2-#5410/2]

	#<z> = [#<_z_top> - #4]
	o101 while [#<z> GT #<_z_bot>]
		G3 X[#1+#<r>] Y[#2] I[-#<r>] Z[#<z>] P1
		#<z> = [#<z> - #4]
	o101 endwhile

	o102 if [#<_z_top> GT #<_z_bot>]
		#<ang> = [[#<z>-#<_z_bot>]/#4*360]
		G3 X[#1+COS[#<ang>]*#<r>] Y[#2+SIN[#<ang>]*#<r>] I[-#<r>] Z[#<_z_bot>]
		G3 X[#1+COS[#<ang>]*#<r>] Y[#2+SIN[#<ang>]*#<r>] I[-COS[#<ang>]*#<r>] J[-SIN[#<ang>]*#<r>] Z[#<_z_bot>]
	o102 endif

	G0 X#1 Y#2
	G0 Z0

o<bore> endsub

M2