G2

What I am trying to do: in a 1" x 1" square workpiece, cut a .68" ID hole starting at (.16",.16").  The mill is .125" nminal diameter.  It is actually .122".

The gCode I tried, producing a hole that is too small:

g1 x.16 y.16 f25
g1 z0 f25
g2 i.-34

What have you set as your tool diameter and how much is 'too small'?

I may have solved it. There are dozens of G2/G3 examples on YouTube and only one seems to provide useful instruction.

What video on youtube?
It might be helpful to others ...

was the only useful one for me. This is the bash scrip that I wrote to produce a hole centered in a box specified by four points. There are two files that this script uses.

#!/bin/bash

# Cut an interior circle starting at xStartBB yStartBB xEndBB yEndBB zStart zStep zEnd feedRate holeDiameter endMillDiameter

# BB is short for BoundingBox

if [ "$#" -eq 0 ];

then echo "$0 xBB yBB xEndBB yEndBB zStart stepZ endZ feedRate holeDiameter endMillDiameter"

else

xStartBB=$1

yStartBB=$2

xEndBB=$3

yEndBB=$4

startZ=$5

stepZ=$6

endZ=$7

feedRate=$8

holeDiameter=$9

endMillDiameter=${10}

millRadius=`echo "$endMillDiameter/2"|bc -l`

# Calculate starting cut points

echo $xEndBB $xStartBB $holeDiameter

center=`echo "(($xEndBB-$xStartBB)/2)"|bc -l`

offset=`echo "((($xEndBB-$xStartBB)-($holeDiameter))/2)"|bc -l`

startXCut=`echo "$xStartBB+$offset+$millRadius"|bc -l`

startYCut=`echo "($yEndBB-$yStartBB)/2"|bc -l`

endYCut=$startYCut

endXCut=`echo "$yEndBB - $offset - $millRadius"|bc -l`

# calculate radius for i

i=`echo "($center-$startXCut)"|bc -l`

cat prolog.nc >rotate.nc

echo "g1 z1.0 f$feedRate" >>rotate.nc

echo "g1 x$startXCut y$startYCut f$feedRate" >>rotate.nc

echo "g1 z$startZ y$startYCut f$feedRate" >>rotate.nc

newstartZ=`echo "$startZ+$stepZ"|bc -l`

for curZ in `seq $newstartZ $stepZ $endZ`

do

echo "g1 z$curZ f$feedRate" >>rotate.nc

echo "g2 x$endXCut y$endYCut i$i j0 f$feedRate" >>rotate.nc

echo "x$startXCut y$startYCut j0 i-$i" >>rotate.nc

done

echo "g1 z1.0 f$feedRate" >>rotate.nc

cat epilog.nc >>rotate.nc

fi

The two external files are prolog.nc

%

g17 g20 g54

and epilog.nc

m2

%