KS 21: Hammer Prepping Off-Rail and Pinning

KS 21: Hammer Prepping Off-Rail and Pinning

Now, prep hammers (and wippens if needed). New parts might be considered here, a subject for another day. Same with new materials, rebushing, and other restorative measures. For regulating, accepting features as-is must often be part of a budget and strategy that best helps our customer. But in every case, the hammers should be prepped. If pinning needs adjusting, tails are chewing up backchecks, or repairs are needed, if multiple hammers will have to come off their rail, consider removing them all to be filed at the Hammer Filing Jig. Gang-filing flared hammers distorts their shape and one-by-one filing requires much skill and significant endurance. Using an electric screwdriver and having the hammer scale to come back to, removing and reinstalling hammers goes quickly. 

To best use the Hammer Filing Jig, press thumb on tip of molding (see lead photo) and gently feed hammer into the sanding drum while guiding the shank around with a finger from the other hand. File in one continuous motion, applying more or less pressure as needed. Work from the more visible side of the hammers to the less if felt will allow. Sometimes, the other direction will be necessary, and occasionally, you may have to work both sides up to the crown as in traditional hand filing.

In any case, this method offers great control of shape and surface quality. It does depend on the underside of the hammer being flat and parallel to the topside, i.e., hammers with too much taper will cause trouble. Most flared (bass and tenor) hammers have flat enough sides for the jig, but many treble hammers, particularly in the high treble, do not. Steinway, for instance, used to taper high treble hammers virtually to the crown. For this reason, wait until hammers are back on to gang-file the straight-bored sections.

Why were top hammers so thoroughly tapered when clearly not for clearance? Less weight, as we know, is the answer, to benefit tone when striking the shorter, higher-pitched strings. This can also be a reason to modify the inherited tail shape. In the photo below, bass hammers were weight-challenged, requiring extra compensatory lead in their keys. And that excessive tail mass extended all the way up the scale, so for both weight and tone, I reshaped these tails. Sometimes, overly rough tails can offer a third reason. Doing this work at a disc grinder (100-120 grit paper) makes neat job.

When tails are at finished weight and hammers have been filed, check out the pinning friction. This should be a reasonable compromise between enough friction to provide stable travel, bounce, and bushing wear and enough freedom to meet whatever demand for speed is asked. I was told to pin to 4.5 swings, which my teacher taught as half-swings. Now I believe that should have been 4.5 whole swings. A solid 9 half-swings plays like a demon but has consistent travel and bounce, especially when hammers move vertically. For the as-yet-unfiled treble hammers, pin to 10 half-swings. The swinging method has the advantage of adapting friction to hammer size, heavy hammers needing more control, light hammers more freedom.

Often, working a bushing that is tight from inactivity will loosen it enough. When it won't, treat bushings with 50-50 alcohol and water and leave them overnight to dry. A new, half-size larger pin may be needed, depending. My goal is to end up close enough to loosen into place by working and/or lubricant (Protek CLP) or tighten into place with a sharp-pointed broach.

Yes, tighten. Using the tip, push firmly into the bushing's cloth and work in a circular pattern. Then, work flange and shank against the center pin to compress the place in the cloth just treated. This produces dependable results that last as well or better than re-pinning. Administer the procedure to both sides of the shank at points that mirror each other to not disturb travel or spacing. Between working and tightening, a set of hammers can generally be brought to 9 half-swings each in less than half an hour. This makes a huge difference to the feel and control of the action but, of course, the hammers have to be off their rail. Treating knuckles can be another off-rail benefit: replacing, moving, or bolstering.

Check out a sample wippen. Wippens make much less difference to the end result but contribute. The wippen flange should produce 1-3 grams resistance, repetition lever 3-6 grams from the long end (1-2 grams is typical and acceptable but not preferable), and jacks 1-2 grams at the tip end (ideally each jack will fall gradually of its own weight when springless and horizontal). And the more even all three of these are note-to-note, the better. Are there silk loops that might break? What are the states of graphite surfaces and wippen cloth? Loops and pinning would require parts off, of course. If the wippens are old, off-rail can also allow for checking and glue-tacking repetition lever posts and jack elbows as needed.

Above, see 100 year-old wippen heels before treating. A drop of Dampp-Chaser humidifier treatment in the middle of each depression followed by firm pressure from a hot flat iron (on wool setting) creates the results shown below. It does sometimes take more than one pass, but it is fast.

This won't solve wear, but it undoes compression to a surprising degree without having to remove parts. Wippen heels can also be bolstered...

Hammers and hammer pinning make the most difference to tone and playability. If verdigris is present in any of the bushings, use the cleaning agent Fantastic first. Then, look to refinements of work/lube and broach.

Next week: Key Steps Index

(Index of all articles in this series)









1 comment

David kollar

As an experiment I’ve tried the “fantastic “ treatment on problem Steinway flanges and have most impressed. Still no substitute for replacing parts. I find I have to let the treated parts sit in the shop for at least 24 hours for best results

David kollar

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