Everyone, I've been following the discussions on the M&H BB pinblock. It think it might be constructive to differentiate between a doweled pinblock and a fully fit pinblock. For starters, all doweled pinblocks are fully fit, but not all fully fit pinblocks are doweled. From the manufacturer's standpoint, his fully fit pinblock is almost always doweled. This begs the question: why are factory fully fit pinblocks doweled to the stretcher? Certainly in the case of Steinway (and this reasoning is applicable to other brands), the pinblock and stretcher assembly are glued together in a press long before the case into which it will be installed is present. As we know, when gluing two pieces of wood together the glue acts as an excellent lubricant when the moment comes to clamp up, and the members of the assembly slide wherever they wish. Steinway's five blind dowels keep their pinblock/stretcher assembly in alignment when the two components are buttered with glue and forced together in the press. I've done the math, and the surface area of these five dowels adds a mere 7% of additional surface area to the joint. For my money, this constitutes negligible additional strength. Thus the dowels are present for ease/accuracy of manufacture. With both the pinblock edge and the back of the stretcher well surfaced on a jointer planer and dry-fit air tight, that 1.5" tall by 52" long glue joint is quite sufficient to bond those two wooden members for 100 years or more. We all know the veneer on the back of the stretcher sometimes comes loose from the core lumber before the pinblock/stretcher joint fails. Notwithstanding, if the piano is designed and built properly there is little-to-no stress on this joint. Now let's focus on the rebuilding end of it. We as a trade tend to omit the blind dowels for two reasons. First, when we clamp and glue the pinblock into the case, the stretcher is already present. It is immobile vertically and laterally. With the new pinblock fully fit to the insides of the outer rim at the bass and treble ends and ready to mate up to the back of the stretcher, there can be no lateral or fore/aft sliding of the pinblock during glue up. It's captured within the case. Therefore dowels would serve no mechanical expedient. Assuming the rebuilder installs the plate and new pinblock simultaneously, the plate serves as the final vertical tweaker of the pinblock elevation in the middle of the scale. While the glue is still wet, all the plate webbing screws are installed to cinch the block up to the underside of the plate in the center, then the stretcher is clamped home to the edge of the pinblock reestablishing the factory-style fully fit pinblock joint. If dowels are to be installed subsequently, the plate must then be removed once the glue has cured to "toe" the dowels into the stretcher through the top layer of the pinblock at a shallow angle (new Mason & Hamlin pianos are reinforced in this exact manner). Few rebuilders wish to remove the plate once it has been finally installed. Time is money, and we all lose it quite nicely, thank you. Thus rebuilders by and large churn out fully fit but not doweled pinblocks (and yes, some factory pianos we all have encountered have sported this type of joint, too). Personally this un-doweled version is my preference. I am certainly aware there are other meritorious ways to acheive this joint. To each his own. I do however endorse the three-sided (bass end, stretcher, treble end) fully fit pinblock in all brands of piano. For me, omitting this step is akin to ignoring a continuous inner rim/outer rim separation or a loose crossblock within the case. I want to do everything possible to make the piano a wooden fortress. Dave Hughes, RPT Baltimore Chapter
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