Ron - what kind of a lead angle are you getting on your notches? By that, I mean approximately what is the angle (tangent) of the face of the notch at the top of the notch when it first starts downward from the bridge top? That make sends? Maybe more accurately stated, what is the angle made by the bridge top and a tangent to the uppermost portion of the notch face? Yeah, that's better, I like that. Dog-gone fine-looking notches! Have you tried the Steingraber bridge agraffes yet? Are you tempted? What do you think of them? Terry Farrell On Oct 17, 2010, at 10:17 AM, Ron Nossaman wrote: > 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 > <cap laminations.JPG>
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