This week, I will touch on the importance of regulation sampling and the possibility of further preparation steps based on what you find. Geometry may need tweaking if normal aftertouch requires too much dip, notes feel too heavy, notes won't repeat, or parts poorly align. Materials may need attention if indentations will conflict with new spacing or cause other problems. Hammerline may be overly elevated after multiple hammer filings and need action adaptations. My suggestions will all be quick-ish fixes where a more thorough restoration or replacement of parts would exceed budget.
But first, let me remediate a point from last week's chat. What is step one for centering jacks in repetition lever windows? No, sorry, trick question. Rep lever validation or realignment is the answer. Correcting jacks to incorrect rep levers causes traveling, squaring, and spacing trouble for wippens. This should be an off-rail adjustment, but if there are only a few, individuals can be removed during on-rail prepping. You could support rep lever post arm and tap tall end of rep lever with hammer (a-la-jack-centering) to bend center pin to true alignment. This is fast but can result in birdseye or post arm damage. Which brings up my opinion of tapping jacks: Don't do it (unless you're in a pre-concert negative timezone). Tips of jacks are slide-sensitive surfaces you will mar with hammer steel. And associated jack or wippen damage is a time-wasting setback. For both jack and rep lever spacing, remove old center pin, push a suitably-sized new one through, bend it with jewelers pliers, and push it back just the right amount. If double-think confusion bent pin in wrong direction, push bend free of birdseye, vise-grip pin 180 degrees, and push into right place.
Now, fully regulate two to three sample notes. Discovering the need for a global change as you approach the finish line discourages. It does also teach, so if that's what happens, learn lesson. However, avoid heat at back of neck, ache in heart and stomach, and general embarrassment by sampling. The key leveling previously done will simplify this. Choose a cluster of notes (preferably natural-sharp-natural) in the bass, because this area is most sensitive to effects of weight, inertia, and friction. And the 20 grams minimum upweight simplifies analysis. If a note won't lift upweight, a tweak must happen. This could be as simple as removing one lead from the front of one key or it could be the "tip of an iceberg", asking for global remedy.
Have a look at the lead photo. Wippen heel nicely centered over capstan, jack with an angle of address to the knuckle that aligns with knuckle core (perpendicular to shank with tip tangent to knuckle surface for best power and best sliding through letoff), shanks a suitable distance above rest cushions (in this case a height-adjustable rail). Good. This style action has slots in the wippen rail, making it also adjustable. The down side of this adjustability is that in older actions, screws can become loose enough over time for the rail to shift (wood swells against screw in damp weather, compressing itself to become loose in dry weather). Wippen misalignment with both capstan and knuckle would be a symptom of this and correctible by tightening rail back into original location. What next? A check of spread distance, perhaps, if one or more of the items above is not right. For this action, 112mm (see photo below) is what I would expect and the good part alignment validates this. Note #1 works for a photo, but as for representing the rest of the piano, it is an outlier. Choose samples further up the scale and remove neighboring parts to measure as needed.
Blow distance and dip need to be in the "expected" range and aftertouch neither excessive nor pinched. Jacks must not jam against their rep lever windows but must fully clear knuckles. Part relationships should meet normal criteria. If they do, the action will work smoothly. If the sample keys lift 20g upweight, but require an overly high downweight, consider options. If these bass keys lift well above 20g and the parts align, consider adding a well-calculated amount of lead to keys. This may, however, require removing lead first and the plugging of many holes. Weighoff and plugging may be right things to do, but this kind of global work will need substantial extra time and deserves extra compensation. Probably out of scope.
If you are facing a lot of capstan turning to lift hammerline to its best location, consider un-dimpling the wippen cloth. I use a drop of Dampp-chaser additive (a serious surfactant), followed by wire brushing and a burnishing with hot flat iron on wool setting. More than one pass may be needed for best results but don't be tempted to try all in one go as too much additive may release cloth from glue (if water-soluble). Note in the photo below how much down-turning of capstans I faced after applying this procedure to an already regulated hammerline...
In a worn action, all parts will have received wear and seasonal stresses and hopefully lots of playing. A line must be drawn in the hour glass sand, not necessarily an easy call as to when or where since that sand is in motion (and glass is in the way). But it is important not to leave big-impact items out or dwell too long on those that don't count for much. In the early days of my career, I spent a lot of time (and my customer's money) changing upright sticker cloth. I could do such a neat job of it. It looked better. But there may have been more pressing issues.
Next week: Further Discretionary Prep