by Alan Carruth » Fri Nov 24, 2017 2:22 pm
I've been roughing archings with a drill press planer all along. It's basically an end mill, with a cut about 2" wide. I draw up a contour map in 2mm steps, and cut out areas of it to allow me to use it as a master to trace onto the plates. Once the bottom side is flat the top is taken down to the maximum height, and the first contour outside of that traced out. The planer is lowered to the correct height plus, say, a half mm, and everything outside of the line is removed. Replace the map, trace out the next contour. Lather, rinse, repeat. I usually leave the edge flat at the 5mm level until the outline is finalized. It takes a couple of hours to get the contours all milled off: I've removed about 90% of the waste. If you're careful, and always leave the line, its not too hard to get the final contours right with arch planes and scrapers.
Note that the one I've got is a Wagner 'Safety Planer', which is not made any more. Using the word 'safety' in referring to any power tool is a stretch. I've been bitten a couple of times (in over forty years of use), but never when I've been roughing arches. OTOH, I had a student who couldn't seem to avoid it. I usually use it to thickness sides, which is relatively safe, since the cutter is down close to the deck, and the lip that overhangs the cutters offers some protection. When roughing contours the cutter is up off the table far enough to get your hand under, and that's scary. Which may be why I've never been bitten doing this (knock wood). You do have to be very aware of where the outside edge of the tool is, and not lose sight of that in concentrating on the cut line. Other than that, my main safety tip is to always keep your fingers pointing away from the tool. You can set your hand right in top of it when it's running with no problems, but no matter how low it is you can get a finger tip in underneath. That smarts.