best cnc bit for .080 & .040

Our favorite has been onsrud 63-430

 

Onsrud single fluted spiral o's upcut always worked well for us. https://www.hartlauerbits.com/63-600 The 3/16" cutting diameter bits were a great balance.

speed and feed are extremely important for a good cut and a determining factor on how long the bits last. Tiny needle like chips mean your building up too much heat and the cut will eventually look like it's melted. The heat will ruin the bit as well. You want to shoot for thin potato chip looking chips...

Your cutter doesn't weigh enough for perfectly smooth cuts. The more expensive machines use mass/weight to dampen vibrations giving you smoother cuts and the bits last longer.

 

Any cutter will work on that stuff but generally speaking, "O" Flute is best.

Hold down matters more than the bit. Thin material can be a PITA to cut if you don't have a really good vac table.

 

It's been many years since I ran a router. We downloaded a basic guide from somewhere. Here is a calculator to get you in the balpark after you settle on a bit size and number of flutes.

 

This should help you out selecting the right bit for the material you will be cutting.