I am testing the assembly of my new clock design and ran out of 1/2" MDF. I ran down to my local Home center (HD) and picked up a 2' x 4' sheet.

I brought it home and now I remember why I hate MDF in general. This stuff is like a dang rock. Its nothing like the last batch I got. I cant cut a decent round hole as it causes the 1/8" bit to deflect, even at slower speeds.

Overall I can cut the stuff with enough accuracy for all the other parts of the clock. But since the holes have to support brass tubes nice and snug, I am having problems.

So my fear is that if I generate Gcode and others download the code they may not get consitant holes based on the material. I am tempted to just jave the CNC peck a 1/8" pilot hole and dirll the actual holes with a drill press. That way I know the holes will be consitant no mater what the material.

I guess I could slow the CNC down to a crawl but Im afraid I will burn up the bit. I am takeing a 1/8" cut per pass. Would I be better off keeping the speed up and just reducing the cut depth to 1/16" when I cut the arbor holes?

Keep in mind I am using a two flute 1/8" spiral upcut bit.