On 10/17/2010 12:28 AM, jimialeggio wrote: > As I play with various radius cutters, I'm staring at and wondering what > relief is actually required to safely stay out of the way of the string > excursion. Obviously it varies treble to bass, but immediately after the > pin, I wonder what clearance is actually necessary. A 7-1/2" cutter > would allow me to get away with a relatively easy (keeping in mind that, > relatively is a relative word) table saw jig setup I have in mind, but > looking at the cut in the shop, I think I would have to follow up the > machine notching with swipe of a chisel(darn, but still allows me to use > a laminated cap). I chose the 2" cutter for a number of reasons, like cost, power requirements, notch edge definition, and such. Look at the notching in the pianos you tune. You'll find more than a few radii that a quarter fits neatly into. The bigger the radius, the harder it is to index the cut accurately, and the more the string contact point advances into the speaking length as the notch edge crushes with time. > With the 2" cutter, that's probably a 1/2" shaft you've got there. What > is the clearance between cutting arc and the top of the pillow blocks > you used? With that size cutter, the way I figure it, its probably about > 7/16" clearance. The arbor is outboard of the bridge, at least for grands, so the bearing doesn't pass over the bridge at all. Even doing a bridge that curves the other way, the arbor clears the bridge top. I couldn't find an arbor of a size I liked at the time, so I made this one. > Also with that style cutter have you noticed a tendency to beat-up the > side cut of the notch. Cutting rabbets with flat top groovers can be > prone to tearout, and in this case I see the side of the notch, from the > cutter's perspective, as the moral equivalent of a rabbet. Not quite. It's a climb cut, so it's a down shear from the top. There's no tear out whatsoever. See photo. I left it big so you could zoom in close. > ...On the kitchen table, sits the all important > "back-of-the-envelope"....upon this precious piece of discarded paper, > accompanied by lovely splatterings of tomato sauce and cantaloupe pits, > all my important design decisions are made... I ended up with a half dozen 8.5"x11" sheets of sketches, notes, part numbers and sources, and coffee stains. The rule is, never design in hardware. We do, ultimately, to make what we designed on paper work something like we hoped it would when the original build didn't quite, but that'll come soon enough. A table saw? How does that work? Most everyone who thinks about building a notcher considers a compound miter saw at some point. I did too, but the motor size and required cutter diameter, hold down, feed control, and resulting portability didn't fit the mental picture. Ron N -------------- next part -------------- A non-text attachment was scrubbed... Name: cap laminations.JPG Type: image/jpeg Size: 876512 bytes Desc: not available URL: <http://ptg.org/pipermail/pianotech.php/attachments/20101017/4696651c/attachment-0001.jpeg>
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