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Yes, I'm still a long way off from doing so but I'd like to know if there's any possibilities of using a CNC machine to drill a lot of holes. Right now, I've got to drill roughly 180 holes in my standard instruments and when I finally get around to an instrument with a key change mechanism, that number will be well over 400 (at least with the design that I've got in my head at the moment.

In the first picture, you can see all the tuning pin holes I need to drill, and the holes in the bridge. On the tuning pins, I use a 3/16" brad drill and according to the various speed charts, you want about 750rpm +/-. These holes have to be very tight and not burnished or burned or anything. Are there any affordable spindles that can get down to the 1000rpm range or is there any other method of doing so? I imagine that using a 3/16" router bit at umpteen thousand RPM would burn and just yuck up the hole in general.

For the bridge, I have to drill a hole for each string. On top of that, each hole is angled to force a break angle on the string. Most of these holes are around 1/16" in diameter (though I'd like to go smaller for the plain steel strings) so I don't think high speed would be an issue. To do this right now, I use a fixture like the one in picture two to drill the holes. I could see how with a 4 or 5 axis machine you could tilt the spindle head to get the right angle but is it feasible to use a fixture like the one I have for the angle and move the head accurately enough to get it right? I do understand that my fixture would need indexing. It also seems like I'd need a small head to not bump into the bridge while drilling the low strings.

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Oh most definitely. Depends on the software but most good Cam programs will allow you drill as well as project the drilling on the 3d model so the depths are correct.

Mike

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Hello, I'm new to this forum (and lutherie), but I'm a long-time woodworker/CNC owner. I second Mike's observation on the CAM software. As far as the 'hardware' is concerned, a spindle attached to a VFD has the capability to vary RPM, which will be key to avoiding the burn / burnish problem. Other important considerations are bit type/sharpeness, and plunge speed. It's tricky sometimes. What I've done in the past is 'cool' the drilling process with compressed air, which also helps in chip evacuation--the main problem in burning holes.