Quote Originally Posted by Alex Zeller View Post
I've used bits as small as .030" I bought from ebay. I think they were used for making holes in circuit boards. I have yet to break one. But I have a spindle, not a router. I usually use what Amana suggests for feeds and speeds for similar bits. I think the bits are 1/8" shank but not sure. I also have some 1/16" bits from the same seller. It amazes me how fast the cnc moves with such a small bit. I use the small bits for doing inlays.
My smallest is a .023 three flute cutter for fret slots. I also use a spindle and worked out the best feed/speed with Ron from Precise Bits/Tinker and Tinker on the phone. For my particular setup doing 5 passes to get to 2mm depth, the math worked out to 18K RPM and 24 ipm. It's worked flawlessly. That particular piece of tooling has a .125" shank and I use a .125" collet. (I regularly use 1mm and 1.5mm tooling for some details on resin inlay toolpaths on charcuterie boards I cut for a friend to get corner details)