There really isn't a program to directly convert a dxf (drawing exchange) file to gcode instructions.
Gcode is a set of instruction on how to cut geometric features which has numerous parameters for control.
A dxf file is simple geometry and does not contain enough information to properly control a machine.
For instance, take a circle that may be in the dxf. You may want to cut on the inside of the circle, or the outside of the circle. The cutting would need to be half the diameter of the end mill from the geometry so the edge of the end mill cuts along the line. There is also the speed to cut the geometry, how deep to cut the geometry, etc. This information does not exist in the dxf file.
A CAM program, like CAMBAM, Cut2D or other Vectric software, MechCAM, etc that allows you to apply machining operation to the dxf geometry. These machining operations are what is converted into Gcode.
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What is the best program to use for converting a .DXF file to a G-Code file to use with Mach4. Mach4 will be used with a drill table.