Metal hand Saw machine

Using a carbattery, a lightswitch, a car-window-wiper-motor, and a 3D Printer, i've comprised a simple automatisation for the metal handsaw.
For even, straight cuts of INOX 316 & 304 linear rods,
electric tools were too violent, and resulted in ugly sawcuts, burr and slivers.
This is my 60$ weekend solution to a +300$ slowcutting metalsaw.
I figured that, if i added an arm to the wiper motor, i could make a circular motion,into a repetitive, linear one.
The next step was the math.
If i added an arm with a radius of half the distance the saw needed to back and forward,
the complete diameter would bridge that needed distance.
The saw had a travel of 137MM from center to M3 pivot-hole at the end is 137mm/2=68.5mm

I can saw about 2x 8hrs before the battery tells me to do it myself.
So i've searched the web for a simple solartracker ardu sketch, uploaded it to a ArduProMini16mhz, aquired a set of LDR's, fished a servo out of my modelbuilding shoebox, and sketched a solartracker