Since my name has come up in this thread, I will put in my two-cents worth, at risk of repeating myself. RonN wrote: > I try to keep front and rear bearing angles roughly equal, but it's really > not all that critical. As long as there is a total bearing angle in the > range you allow, without a negative front or rear angle, it'll be fine. I totally agree, but how do you know you are "without negative front or rear angle?" Holding a 6-inch rule solidly on its edge on the top face of the bridge, bending it slightly in toward the speaking length, you can often see it pace above the speaking segment at some point away from the front bridge pin. If not, you can usually see that the string is angling lower than the rule. Doing the same on the duplex side, you can verify positive (or negative) bearing. This yields no numbers to crunch, but it does help to rule out negative bearing, while validating your numbers measuring overall bearing as Ron describes. Using an "external" reference, such as the top edge of the rim unduly complicates things, I would think. The optimal reference is the top face of the bridge in the vicinity of the string angles being measured. If you cannot work out an arrangement for the base of the gage to reference this, the above is the next-best thing. Keep in mind that there are pianos out there that were manufactured with significant negative back bearing. I would hope that this was done inadvertently, but you never know! I have seen manufacturers' drawings that clearly indicate an intentional zero-bearing on the back side, with the total down-bearing applied to the front side. I believe this to be a bad idea, but pianos are out there that reflect this misbegotten notion. One more point: I would shy away from attempting to zero-out the presumed top face of the bridge by referencing the string segment between the front and back bridge pins. Although some insist that it is impossible for the string to ride up on the bridge pins, I have seen it and measured it. If you suspect this to be the case, use the depth gage of calipers to measure the strings "thickness" just in front of the back pin; then measure the same just behind the front pins. If the string measures "thicker" at one of these two points, try tapping the string down, and re-measure. This condition would most likely occur if you have negative bearing, but you can't rule it out even if there is positive bearing. The bottom-line is that I would prefer the reference the top of the bridge where possible, and not trust referencing the string segment between the front and back pins. Frank Emerson
This PTG archive page provided courtesy of Moy Piano Service, LLC