Thanks for posting those pictures. Admittedly, Im having a hard time visualizing how you use all this to actually cut the rib. David Love davidlovepianos at comcast.net www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Jude Reveley/Absolute Piano Sent: Friday, August 08, 2008 5:41 AM To: Piano Tech List Subject: Cutting rib radii As for methods of cutting rib radii: There's ye ol' router sled (see picture). You'll need one per radii. Michael Morvin makes the best templates (picture posted) for all your crowning jigs from rib presses to cauls to sled runners (picture posted) and I bought a few before I finessed my router base, based on the old sailor's trick that Andrew Anderson described or Ron N. You'll need to know the deflection for any given radii which is r-(r^2-(c^2)/4)^0.5 where r is the radius and c is the span. I readily admit that while this router base works outstanding, it was way more expensive to put together than buying Michael's templates. I only have one "fixed sled" which I've used for the longest ribs on my more traditional projects based on a 50' radius (I thought this was quite aggressive when I was young<G>). This was supplemented by variable radii ribbing by an adjustable crowning sled (see pix). This sled works surpisingly well and I never went beyond the working model which I built eight years ago. It crowns ribs up to 90cm in length. The center of both runners are supported by capstans, which refine the crown as well as support the weight of the router. I set the crown by turning the turnbuckle underneath, adjust the capstan in the middle and verify crown by sampling measurements every inch on each side with a height gage. As far as thousands of an inch can measure, I'm producing arcs but even if they were catenaries or parabolas, it doesn't matter. Jude Reveley, RPT Absolute Piano Restoration, LLC Lowell, Massachusetts (978) 323-4545
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