Leaning to mill on a CNC, one mistake at a time. An accident is a series of mistakes. they key is to know when you are about to make one too many. Last night I broke the smallest bit in my set of milling tools, and I should have seen it coming. I have to go through a lot of steps to cut something on the CNC machine: First, a design has to be created in software like Alibre.  Once all the interconnected parts are shown to be Ok, I take each piece in turn and export it to DXF, and then import those DXF into Cambam.  In Cambam I set up all the machining operations -- cut here first, then cut this bit but only so much, then profile this part, etc.   Then the Gcode is walked down to the CNC.  Once I fire up EMC2 in Ubuntu I power up the machine and I "home" the machine.  Homing is how I tell the machine where 0,0,0 is located.  That way it knows "I go X from here, drill down Z, move sideways Y, etc" and I get the shape I want in the spot I want.  Generally z=0 is the table top. At first I cut an involute gear, and everything was great.  I was so pleased with myself.  One step closer to profitability!  There were a few "huh, that's wierd," followed by an equal number of "oh well, I'll figure it out later.  This software is pretty