What mill bits?

[Jonathan]

The 6mm single flute cutters mentioned here will be excellent for the aluminium. Look at the parts I cut that are in luke11cnc's build log to see the finish...

However fiberglass is going to be much more difficult. Since it looks like you'll get some for aluminium anyway you might as well try it. I expect they will not last very long at all as glass is very hard and abrasive. I've cut some parts from carbon fiber and texalium sheet (so fairly similar stuff) and HSS tool lasted a few seconds and carbide a few minutes so both basically useless. You want diamond ... but that's expensive so I tried those cheap diamond burrs you get with rotary tool kits and it was excellent. 2mm diameter, highest spindle speed and something like 300-500mm/min (can't remember exactly but it was slow). The finish is good as you're grinding it. People who are fond of health and safety will mention at this point that the dust is very bad for you.




The second photo is before I washed the dust off, hence it looks a bit bad...