KS 14: Bedding and Key Level Sampling

KS 14: Bedding and Key Level Sampling

To turn a key into a bedding sample, remove its front punchings, install a Keystep, and turn that up to just touch. The key at rest already contacts both backrail and frontrail. Now it touches all three rails and becomes a gauge for front-to-back keyframe shape. Too much friction at key, wippen, or hammer could make the key's rest position unreliable, undermining sampling accuracy. But we have addressed excess friction (Key Steps for Grand Regulating 12), so how it sits on keybed and benchtop will only differ by shape of keyframe. And when key and Keystep make contact on the bench, the keyframe under that key will be the same shape as it was in the piano. Add correct strike and that note will regulate as if it were in the piano.

The key-Keystep contact implies a tolerance. As long as the key taps the Keystep, they are not in contact. But once the tapping stops, the test only tells us there is contact. Using a WNG Keyframe Bedding Tool, as long as the indicator moves when the Keystep is turned, there is too much contact. The perfect spot lies where there is no motion and no tap. I use the just-eliminate-the-tap half of this method with good results. It's similar to tuning a string and leaving it exactly right with stability. Awareness can estimate the spot and the body can learn to coordinate with that awareness. And the resulting tolerance is very tight, indeed, too tight to show up as an error in our regulating.

The go-nogo procedure of tap-notap proceeds quickly. Because the Keystep's slot necessarily has play front-to-back and side-to-side, push the Keystep against the key pin and center it under the key, a fine-positioning easy to reproduce on the bench. Press firmly on the key (and Keystep-keyframe below it) to turn the Keystep up or down without changing its position. Then, release and tap. Use the ratcheting end of the wrench to quickly make multiple turns in one direction and the open end for fine-tuning. The tap becomes higher in pitch and more faint as it nears contact. Carefully just eliminate the tap.

The keyframe and cheekblocks have been bedded first, of course, and the cheekblocks secured. Pre-level notes A1 and C88 (or A85) with cut punchings. Choose finished key heights (considering case parts, key pins, and action geometry), cut right-sized punchings for pin access, and tweezer them onto the balance pins under the keys. Now, those outermost naturals won't have to be touched up after leveling. Raise 1 and 88 even if not leveling keys, though, because the straightedge for a mid-range leveling sample must clear all other keys to be accurate. The first time the topstack comes off, remove cut punchings and either replace them with whole punchings or discard.

Keystep-reinforced 1 and 88 support both straightedge for naturals and Rocke Blocks plus straightedge for sharps. Turn the  E44 mid-range level-sample Keystep up so key just touches straightedge. Tap test the connection, checking 1, 44, and 88. If Keystep is too high, one end of straightedge will begin to tap and lose contact friction with its support key. Too low, middle taps. The three-point-contact test quickly fine-tunes the Keystep into memorizing in-piano frontrail shape.

Next week: Strike Sampling 

(Index of all articles in this series)

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