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Well I've been screwing around with this thing since January, and finally have a finished product to show for it. My goal from the beginning of this project has been, not to use a CNC machine to build a banjo, but rather to substitute the CNC machine for the various router and shaper jigs I've used for banjo making in the past. I want to save the hand work for the fun parts like engraving, fine tuning the neck shape, etc. Tendonitis and the likes have moved me more and more into using machines for heavy stock removal and saving my joints for the parts where hand work makes a difference. The CNC is nice since I don't have my hands anywhere near big shaper cutters. My jigs were built with safety in mind, but there's still that occasional kickback that scares the pants off you. I still have all ten digits and would like to keep it that way.

Anyway, on to the project at hand. I modeled the neck in Rhino, and used MadCam to generate the tool paths and G Code. The fingerboard and rim parts I modeled and generated the tool paths in VCarve Pro. VCarve is just easier for me to use for 2 and 2 1/2D modeling. I also use VCarve to cut inlays and pockets. (This first banjo is light on inlay--it will become my lowest priced "standard" model). I have found that even for one-off inlays, I can draw it, vectorize it and cut it with the CNC as quickly as I can by hand, and then I have the file if I ever need to cut another one like it. Everything was cut on an XZero Raptor using Mach 3 and a Colombo spindle.

It has a hollow rim made of interlocking parts cut separately on the XZero. The fingerboard was cut using one of the Precise Bits fret cutters, and it has "built in binding" with the fret slots stopping at the edges of the fingerboard before cutting through. The star and the pocket for the star were cut with by machine, but the engraving was done by hand (really simple engraving on this one, but I'm trying to build a nice instrument at a price point and can't spend the time that I do on my custom instruments). The neck was cut almost completely to shape on the CNC, but still had some fine tuning by hand. I still cut the heel to rim joint with my trusty old spindle sander and a jig.

Anyway, here are some pictures.

Dave

Very nice, and in my opinion, a great balance between hand and machine work. I like the texture on the rim, a feature of Vcarve that I've yet to play around with. What kind of jigging did you use to hold the neck for machining?

Bob

Terrific work.

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Thanks--that balance is what it's all about for me. I love hand building, but also love not hurting! Machines definitely have their place, but so does handwork.

I have a series of jigs that I use for holding the various parts--all of them are made from King Star Board and 1/4" round foam gasket material and use a vacuum pump. I rout a channel inside the perimeter of the piece I'm going to machine with a 1/4" round nose end mill and press the gasket material into the slot. I use index pins on everything. Works great, and it makes it easy to reposition work when I'm doing multiple passes on multiple pieces. I put a few short videos out on YouTube that show some details of this. Here are links to a couple: http://www.youtube.com/watch?v=XmhEA2wQ8OEhttp://www.youtube.com/watch?v=r3vqllp_3AA&feature=mfu_in_order&list=UL
The first link shows some neck carving, the second shows a better look at how the jig works. The jig in that video is made to hold peghead overlays, necks and fingerboards (overlay on the left, neck in the middle and fingerboard on the right). I zero the machine once and then use the G54, 55 and 56 offset codes to position the machine for each of the locations on the jig.

VCarve is a pretty cool program. The back of the rim is made of a phenolic material--it works great for that part of the banjo from a tone perspective, but has always thrown some challenges out there regarding finish. Putting the texture on it sort of took care of that issue while looking pretty neat at the same time....

Dave

Super cool work man. That relief on the back has got me thinking now. I think I'm about 4 months behind you on he learning curve and your results are very encouraging! I spent a few hours programming the toolpaths for my 4 sided scroll setup and will probably try cutting this weekend if my simulations look ok. I still have a bit of work to do to program out some collisions and stuff but hopefully....

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That turned out really nice. Great job.