CNC Router Aluminium surfacing

[Zeeflyboy]

tooling leaving ridges means your spindle is out of tram in one or more axis (ie it is not perfectly perpendicular to the X/Y axis)

The smaller the bit, the less obvious this will be so one solution is to use smaller bits and smaller step overs but you will never get a really smooth surface unless you spend some time shimming your spindle into tram (or if your machine has adjustable tram then even better than shimming of course).

As mentioned above you will always have visible swirls/marks but if the surface feels ridged then look to tramming as your solution. With good tram, it should be relatively easy to polish away the tooling marks with some light sanding.