CNC Torch Table File Adapter
The gcode files from the dxf2gcode toolchain alone will not be effective for the torch table
To address the proper piercing issue, Vann Miller has written a correction script. This script does 3 things. First, it takes out the z values generated by the DXF to G-code Converter (not needed in a 2-axis motion system at hand). Second, it starts a pierce by moving towards the center of a hole. Third, it rotates the torch around a small radius (.05") during preheating. The number of rotations is currently 8, but one should be able to modify this.
To run this correction script, download the coverter file - make it executable, and run it from command line. Here's Version 0.22 of vanngcode.php -  . This works based on correct understanding of G2 syntax. It also ignores arcs, and only pierces circles on their interior.
php vanngcode.php <file.ngc>
Where <file.ngc> is the name of the ngc file. The converter will eliminate Z coords and add preheating/piercing to circles.
Also, now the interior offset can be set via the command line, e.g:
php vanngcode.php input.ngc 0.3
... would offset 0.3 inches into the circle before piercing. The default offset is .2 in inch units. For small holes, such as 1/4", the value should be decreased to 0.1, which will pierce just about in the middle.