Circles not coming out circular

[ben@customfronts]

Hey all,

Im having some issues with cutting small circular pockets, everyone of them is slightly off as in one edge of the circle is slightly straight making the pocket slightly too small for what needs to be inserted in it.
It seems to happen with different sizes too. The original plans were drawn up in LibreCAD then the toolpaths done in Vcarve, both apps show the circles as being circles but then when cutting they have a straight edge.
Is it possible its related to the drawings or could it be the tool on the machine? it happens with both 6mm and 8mm straight 2 flute cutters, could it be too fast maybe screwing up the circle.

At a total loss right now.

Many thanks in advance for any help or tips people can provide

[Charlie_l]

Does it look like it is correct in the previews?

[4DThinker]

I'd suspect some backlash in your X or Y axis. Are the flat spots always on the same side as oriented to the CNC? As a toolpath changes direction along that axis, the bit hangs back a little, which on the sides of a circle would look like a flat spot. When the backlash catches up the bit moves as expected.

4D