Router Bits for Three-Dimensional CNC Carving

Advice on tooling for a woodworker who's breaking into 3D CNC carving work. July 29, 2012

Question
There have been numerous questions posted about which program to get to do 3D design work with. I am still stuck between Artcam and Aspire (want to do 3D work but also want to do wave designs and of course cost is a factor). The question (and answer) that I have not seen is what router bits to get after deciding on software. We do nested based cabinets so our router bits are larger (1/2, 5/16, 1/4) and are either straight, down-shear, or compression. What would you consider a good starting lineup that would cover most of your basics (ie: carving, reliefs, roughing, finishing, text)?

Forum Responses
(CNC Forum)
From contributor W:
I use ball nose 1/16, 1/8, 3/16, 1/4, 3/8, and 1/2 depending on need and application. I have done large full (life) size chess players, appliques (eagle globe and anchors) for the USMC in walnut (4.5" thick 72" in diameter) arched and radius trims with cherubs leaning out inspecting the work as installed. I’m currently making "wave" and textured panels for a development clubhouse and theater all with Aspire. I have Artcam yet prefer Aspire.

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From contributor M:
The ball mills Contributor W describes work great, are relatively inexpensive, and would likely be the work horse in your tool kit. Also available are taper ball mills, though they are only worth the extra cost if you have long projections, need to remove a lot of material or need to drive at higher speeds. The advantage is strength in heavier cuts, the tradeoff is cost. I can often save some roughing passes with a taper ball that would snap a straight ball. The Onsrud 77-106 is an example.

Other guys argue that small diameter straight bits get into the small corners more effectively, and to a point I can see this in pencil tracing operations or "rest machining", where you cut the main body of work with a larger bit then go back at the corners with a smaller tool to increase detail.

MSC distributes small diameter straight bits and ball mills in two, three, or four flute varieties. They are made for metal work, but are a lot stronger than the ones made for wood, and I find that difference in cut quality at these small diameters to be negligible in most cases.

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From contributor G:
There are a variety of tools you can use. Contributor W mentioned a few, but also you might need different angle tools such as a 22.5, 60 and 90.

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From the original questioner:
Contributor W - I have seen your chess players and the wave board that you are working on now. Do you do the wave board with Aspire? If so, then that will probably be the program I will go with.

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From contributor H:
I use primarily 1/2" and 1/4" ball nose bits unless there are some really tight corners to get into. I prefer to use the largest ball nose bit that will do the job. For roughing I'll run 1/4" above the final surface with a 50% bit overlap. For final pass I'll use the same bit if I can with a 95% overlap. The larger the bit, the more parallel to the surface, with approximately 5% of the bit hitting the surface. This makes for a smoother final surface with less sanding.