Hammers hung, parts prepped, and action assembled, the regulation must begin with a serious hammerline touchup! A combination of new capstans turned in at speed, wippens with two heel heights, and other variables produces what you see in the lead photo. For key leveling, all shanks must be off their cushions, lost motion eliminated and the overly-lofted brought into a semblance of order. Keysteps under notes #1 and #88 (set to spec in the piano) support the WNG Key Level Stick for naturals, and Rocke Sharp Leveling Blocks on these same two keys support it for sharps. The second step of the blocks (down .008" from the full .5") provides a sharp height with room for a dip that gives good aftertouch while bottoming out proud of at-rest naturals.

 

The sharps, in particular, lie way below the aimed-for height, so far below that piggybacked gauges estimate a round of two-punchings-at-once additions. 

This first round leveling raises both sharp and natural key heights so much that another significant hammerline adjustment is needed.

But relatively little is needed for the second round of leveling to bring all keys within .003" (a white punching) of finished level.  

Key squaring and spacing are next, with keypins tapped into position using a small hammer and a piece of maple. The key heights chosen facilitate this process with enough front keypin in mortise and enough balance keypin above button. And the wood leaves no nicks.

 

After a verticality touchup, hammers go to the piano for final spacing (a spacing scale on the Regulating Rack templates would obviate this trip if the piano were not at hand). Back on the bench, wippens are squared and spaced to knuckles and backchecks to hammer tails. A round of rough dip and backchecking allows for regulating the springs, essential for jack and repetition lever positioning.

And after another hammerline touchup, back of jacks are aligned with back of knuckle cores, first just end-of-section samples with the rest then filled in to a straightedge. The action brackets on this Mason provide positioning for a steel rod along which to sight the jacks on one side and the adjustment screws on the other. The geometric consistency of this straight-line method mitigates knuckle variations.

Although the original hammerheads were slightly bigger, the Ronsen Weickert replacements have too little clearance, several slightly rubbing as they pass. 

The originals were tilted for clearance at some expense to the hammer-to-string fitting process and spacing (the new vertical hammers produce correct capstan, backcheck, wippen, and string spacing). 

A little Dremel Tool sanding relieves under-shoulders on one side of hammers and side of crowns on the other to provide the needed clearance. In some pianos, the scale is too tight and the flare angles too extreme. Tilting may be what you have to do, but I prefer the benefits of verticality when possible.

Another tweak of hammerline and a winking of jacks (to support as much hammer weight as possible without impeding reset) maximizes hammerline stability and transfer of power. The Regulating Rack (moved back a little for this operation) amplifies visibility with well-lit hammers moving relative to stationary, well-lit templates. 

With templates blocking hammer crowns, several glissandi passes, bearing firmly on keytops, compress wippen cloth with capstans and knuckles with jacks.

And glissandi on key ends further improve hammerline (and thereby geometric) stability by settling backrail cloth. Note the use of Gauge Keys (in the photo below) to assure that letoff and drop have the same distances from strike each time.

Hammers are regulated to engage dropscrew and jack tender simultaneously, just touching templates at letoff and falling the optimal amount for drop.

At this point, changes to letoff and drop slightly affect each other, but not to worry. Close-enough-for-now still makes the action weighoff-ready. And the fine-tuning of aftertouch, backchecks, and spring tensions can only come to completion after weighoff and the last round of key leveling are in place.

Next time: Mason A - The Weighoff

(Index of all articles in this series)