I think checking is one of the most neglected and misunderstood events in regulation, A proper tail arc and length combined with the back check's proper height and angle make for a smooth check and better repetition. Bore hammers to follow the string height. A few measurements in each section will map your curve. Allow for 1 1/16" tail length. I add an extra 1/8" for fun since I cut the tail length after boring. Uniform tail length is essential to an even regulation as is a 2 1/2" to 3" arc. Ease the tail edge to remove the sharp corner which contacts the check. Backcheck height should be even with or about 1/16" below the tail with the hammer supported in the drop position with a 68 to 72 degree angle to the key (that's the buckskin face, not the back of the molding). Most backchecks you see have the hammer tail impacting into the check which can be felt in the front of the key. The bottom, leading edge of the tail should not impact into the leather but be slightly away from it allowing the curved portion of the tail to be held by the check. A smooth, almost imperceptible check can be achieved by having the tail scruff into the check. If the leather is dry, replace. Checkering the tail causes more noise than necessary. If the hammer don't check well, replace the backcheck rather than scruff the tails. The more irregularities you introduce, the more erratic your regulation becomes. Different hammer bore heights are not harmful irregularities. Harmful irregularities are whippens which are at different angles, capstan lines transgressing the magic line. Anything that you do to standardize the geometric motion of the each whippen's travel will make for a more even regulation across the keyboard. For touch sensation alone, graduating the Strike Weight is essential. Varying SW's will require varying rep spring tensions. This is felt as the resistance at the point of let off. The closer each adjacent SW is in weight, the more even will be the tension on the rep lever at let off. I could go on... -- Regards, Jon Page
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