Milling aluminum

[nebyeh]

I have been milling aluminum with my diy cnc trimmer router, and it seems to do fine using a 1/4" carbide 4 flute end mill, cutting the full width and taking a .05 depth of cut, at least when I have the router cut left to right, and also using the G02 command, but if I try using the G03 command or cutting from right to left the bit will veer off and dig itself down into the workpiece, what is the difference between the different directions that is causing this?

[Caprirs]

Sounds like climb milling versus conventional milling. The difference is with climb milling, the tool is effectively trying to pull itself into/along the cut. This is the preferred way if everything is rigid like on bigger mills. I'm guessing your router isn't sufficiently stiff to keep the tool from pulling itself into the material.