I'm trying to create G code to cut a slot extending from an existing hole in a sheet metal part.  All the examples I have drive the cutter in an outline of the slot, then clean it out.  I would like to use a spiral cut and take about .010" off each pass to try and extend my tool life.  Imagine a bunch of holes milled as the machine moves the X.  For example I would like to create a slot using an .125" mill aprox 1" long and have a radius on the end of .250.  I would like to do this with aprox .250 radius cuts taking off .010 at a time moving X or Y.

I would like to help BUT I do not have a clue as to what you are trying to do. Can you draw a picture of what you need to do?

(;-) TP

Thanks, I have the beginnings of some code that will work but I need some improvements.  I'll post it when I'm back at that PC if that will help.

Here is what I have so far:

O0001
G20 G40 G80
G00 G90
T1 M6

G00 Z.2
G00 G90 X.5 Y.5 (move to center of circle, in existing hole)
G00 Z-.030 (feed to depth in Z axis, Rapid move hole already exists) 
M98 P0003 L30 (CALL SUB PROGRAM O0003 LXX times)
M30



O0003 (sub to mill circle)

G91 y.01  (Move Incremental Y amount we want to cut for each pass CHANGE M98 above for total distance)
G02 I.04675 F1.2 (move CW to form circle)
G00 G90 (back to absolute)

M99

It results in a circular / spiral pattern.  I would like to change it to a semi-circle / half moon with a mill and a traverse:

I think I have something that will work:

O0001
G20 G40 G80
G00 G90
T1 M6

G00 Z.2
G00 G90 X.5 Y.5 (move to center of circle, in existing hole)
G00 G91 X-.04675 (change to incremental moves and feed out to hole rad-cutter rad,  Rapid move hole exists)
G00 G90 (back to absolute)
G00 Z-.030 (feed to depth in Z axis, Rapid move hole already exists)  

M98 P0004 L30 (CALL SUB PROGRAM O0004 LXX times)

M30



O0004 (sub to mill Semi circle)


G91 y.01  (Move Incremental Y amount we want to cut for each pass CHANGE M98 above for total distance)
G17 G02 X.0935 Y0 R.04675 F1.2 (Cut semi circle)

(Traverse diameter of circle, rapid then slow)
G00 X-.0800
G01 X-.0135 F1.2

G00 G90 (back to absolute)

M99

Well that is one to do it, Just glad I do not have to program it in an arc.

Is there a reason for the complexity over straight line moves and an arc at the end ?

Just curious, (;-) TP

There is already a hole close to the same diameter, just trying to avoid burying the cutter.  I figure if I just extend the existing hole with arcs I can keep the chip load pretty much the same throughout the process.  I may do an outline of the pocket when I'm done to finish it up.