I laid down a straight line to cut in a thin piece of ply, 1/8". Used a 1/4" straight bit with super slow speeds of 30ips, and 5ips for down travel speed. For some odd reason, when the bit plunges into the wood it has a little ‘movement’ prior to cutting the straight line and a little movement upon exit.
It also does this with just about everything I carve. 
