I've been looking for a set of preferably short drill bits (imperial or metric) with a constant 1/4" shank for use on my CNC with my Makita RT0701C router. I'm amazed to find that such a thing doesn't seem to exist. I'm sure I could just plunge into aluminum with an end mill but that seems really wrong when a twist drill bit is designed for such an operation. I'm bootstrapping my homebrew machine by redoing the plates and I need to drill 5mm and 5.5mm holes in aluminum or garolite. Am I missing something? How do you folks drill holes when that's what's needed?
Twist drills are for low-rpm, routers spin too fast. You get endmills that allow plunging (see Sharkbits on Openbuildspartstore.com) otherwise do ramping into the cut in your CAM software.
Ahh, good point about the RPMs. I hadn't thought of that. 10,000 is way faster than they're designed for. My Z-axis is sloppy enough to where there is dangerous resonance (chatter) when I try to do helical operations in aluminum. That's why I'm redoing it. So my only option is to either 1) use a V-carve bit to just mark the surface of the metal (accurately, or at least with consistent error) and then use a drill press or 2) plunge into the metal with a proper end mill I'll look for end mills that are center cutting
I do not know what collets you have, but there are precision collets available for the Makita from Elaire Corp. I originally purchased the 1/8, 3/16, and the 1/4" set. I liked them so much that I bought the 4mm, 6mm, and 8mm set. This opens up a whole lot of endmill options. But if the slop is bad, marking and drilling is probably the most accurate. When I built my CNC I cut and drilled all the aluminum with power tools and a sander. To make sure the holes lined up on two corresponding plates, I clamped two aluminum plates together and drilled a coulple holes though the two and bolted them together. Then I drilled more holes and added enough bolts so the plates laid flat so I could cut and sand them to the template. It worked very well for me.
