An answer: profiles
Jim Yehle in Salt Lake
>Thanks for your kind words, everybody.
I haven't really designed anything, really, just taken historical examples and adapted them. I take catalog drawings and photographs, and using circle templates and rulers, reverse engineer. Sometimes the perspective throws things off, or inaccuracies in the source drawings, but you just eyeball the results and move things around until they look good. I use a computer program, but you could use drafting implements also. Just draw the curves and connect them with tangent lines. (If you download the Vellum files and viewer program, you'll notice Norris and Mathieson profiles lurking in hidden layers in my drawings.) By the way, the tote was far more complicated than the metal side.
Once you have a decent-looking profile, it's easy to draw it by hand or computer full size and proceed. Having everything computerized eased the generation of the CNC programs.
Fine Woodworking published an article about extracting dimensions from (perspective) photographs recently. I just started using an Adobe program called Streamline for converting raster images to line art, but haven't been able to figure out how to request simple curves rather than Bezier splines, which aren't useful for my CNC. At least it gives me a way of importing catalog drawings from Norris etc. into my drafting program.
I aimed for .002 tolerance on the pins and tails, but of course that must be .002 +/- .002 clearance. Tolerance on the profiles can be much wider. I believe that a plane can be dovetailed fine with much sloppier tolerances, especially when using steel on steel, since errors disappear. Perhaps the springback would be greater--I haven't quite figured out the causes of it.
I hope that answers your (first) question
--
Jim
(reverse x and mission to discover real email address)
