KS 23: Hammer Prep On-Rail and Verticality

KS 23: Hammer Prep On-Rail and Verticality

Whether or not hammers received off-rail prep, on-rail prep comes next. This will include solving overly loose pinning if present (the overly tight having been solved before bedding and sampling). Support shanks with a long screwdriver and move it side-to-side. Any shanks that follow with that small amount of contact friction will be candidates. And watch hammers bounce on their rest cushions - more bounce equals less friction. These tests can also find a damaged flange or birdseye. Or a loose hammerhead. If you find one, try them all. CA glue makes a quick passive repair (needing no hammerhead or part removal). If flange screws are snug, any wippens that wobble will also need attention. And, of course, any loose repetition posts or jack elbows or jacks that rub their repetition levers. 

Next comes traveling shanks. Again with the long screwdriver, repeatedly lift and lower groups to spot left and right travelers. This traditional method works well for hurried work but requires a lot of decision-making. Which are right enough to leave as they are and which wrong enough to have to correct? Comparison testing rarely has a clear finish line. The further along in making them acceptable, the more errants show up. And the chances are they do not rise quite vertically however parallel their travel.

Why vertical? Simplicity is the umbrella answer. Although it might be nice to leave as many untouched as possible, verticality will simplify rebound, reduce stress on centers, improve transmission of power, and enhance repetition. Also, if hammers are well-filed and squared to vertical at strike, strings can be leveled and mated to hammers in one step for better tone. In consideration of endgame benefits, I travel to vertical as standard practice.

A simple version of this lowers the Regulating Rack to hammerline, backs the rack up to align with crowns at rest, and chooses hammers that still match the scale for guides. Then, gang-travels to the guides in the traditional manner. 

The Squaring Platform and Shank Traveler render this more accurately. Set up the Platform to be parallel to the plane of the action (same height front-to-back and side-to-side) and extend the Shank Traveler over each shank to reference vertical. Just touch a reference edge to one side or the other of the shank and note visually, tactilely, and, when quiet enough, aurally if the shank is moving into or away from that contact as you lift it through its travel with a screwdriver. This method way reduces strain of choosing and way increases accuracy of results. All the shanks may need traveling, but each will be yes-no matter-of-fact. Once in a rhythm, it goes quickly. Also, the Squaring Platform offers a precise and stable surface for the next step, squaring hammers to vertical at strike.

A Squaring Filing Voicing (SFV) Block has a channel on its underside to sit comfortably on backchecks at approximately the right height and level for squaring to vertical. With Regulating Rack all the way up, shim sample hammers to be at strike. On the SFV Block, hammers stand on their tails, whereas the Squaring Platform lifts crowns to strike by their shanks. Tails can be of varying lengths (those in vintage Steinways, for instance, tapered from 1 1/16" in the bass to as little as 13/16" in the high treble). But then, strike heights can also vary, so shimming crowns to strike sets us up either way. If tails are all the same length and hammers custom bored to strike height, tails will rest in full contact with the squaring surface and confirm that their parallelism is also vertical.

A Hammer Square references vertical for squaring hammers at strike. The Hammer Square Articulated (shown above), has legs that turn in to offer leg edges (rather than leg sides) for referencing and to bring those edges closer to the hammers. This method has the virtue of offering impartial mechanical advice, with a yes or a no answer to the need for tweaking. Heat each shank and square hammers with Hammer Square as needed. When the crowns become horizontal at strike and travel vertically to strings that are level, good mating optimizes tone, increases speed of repetition, and stabilizes delivery and reset, enhancing the player's control. This improves manifestation of player intent. The musician is empowered.

As flare angles approach 16 degrees from straight in bass and tenor sections, clearance can become an issue. Hammer width and rail scale contribute. A seemingly reasonable response to a clearance pinch is to tilt hammers. This trick may be necessary if the action was designed for a tilt or if replacement hammers are bigger than the originals. For maximizing clearance, half travel is where hammers should be vertical. You can't get there, though, with either the SFV Block or the Squaring Platform because wippens are in the way. But you can calculate what is needed at strike and tape a leg extension to the Hammer Square.

First traveling, then squaring changes hammer spacing. Use the Regulating Rack scale at strike to get back to in-piano spacing. If not done already, file bass and tenor hammers individually and compared them to each other as you go for continuity in crown shape and shoulder size. The crowns will be horizontal at strike but if templates are not horizontal (as they probably won't be in the bass, tenor, and high treble sections), they may appear like horizontal steps, only touching their template at its lower side.

For straight-bored sections, gang-filing maximizes continuity of shape and size, but the section crowns should be parallel to the action not the templates (strings in the piano). In vintage Steinways (ideally), shorter tails were coupled with taller backchecks, so the SFV Block will self-position with the crowns parallel. If you're slightly off but consistent, your piano player will not know (and another piano technician would probably not know either) as the results of your regulation and voicing will be consistent, even if not quite perfect. Still, going for the best helps. Be clear on goals ahead of time and only debate the nuances when cornered by a complexity. Then, try to balance considerations to best serve customer interests. 

Filing first with a flat paddle helps continuity and speeds along the process. But be careful not to round end hammers. Shoulders may be slightly tapered at front and back as the section shape dictates (a slight advantage to filing each at the Hammer Filing Jig), but the crowns will turn out well. Finish up with incrementally finer grits of flexible sandpaper strips.

Before the final passes of filing, some pre-voicing may be appropriate. This depends on your experience and sense of what will be needed. A point in favor of pre-voicing is that all hammers (now consistent in size and shape) will receive similar treatment. I use some shoulder deep needling and top-of-hammer work with a compass needle (see lead photo), followed by "attitude adjustments" (Wally Brooks term) with my tool's handle. But when considering  pre-voicing, if in doubt, don't. Wait until you hear what you have in the piano first.

Next week: The Rest of On-Rail Prepping

1 comment

Mike Dugan

I can’t thank you enough for your willingness to teach and share information. This is amazing! Thank you!

Mike Dugan

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