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As I told to sand, re-shape the hammer for making voice mellower.

Is this necessary? If the sand to smooth striking point, the strike mark come back soon. High treble even worse, the felt is too thin to sand.

Comment about sanding hammer welcomed.

Thank you.

Sanding hammers has a number of uses. In new hammers, it removes irregularities in the felt which were either there to begin with or a result of being clamped in the cauls. It also mates the strings to the hammers. In lacquered hammers, it removes irregularities in the lacquering. In old hammers, it removes the grooves, especially the corners of them, which is hardened from wear and makes the tone quite harsh.

When there is not enough felt to sand, the hammers need replacing.

deleting grooves
http://youtu.be/sf1LHhRMwhg

I agree with BDB. If sanding old hammers creates more harsh tone, the piano would benefit from new hammers.

You can try steam voicing though after sanding.

Here's a little additional information: Filing Hammers. Best wishes, Chuck Behm

For institutional/high-use settings, and in an effort to preserve the felt and the life of the hammers, one should first do basic voicing [primarily in and around the string marks] before shaping--this reduces the overall amount of felt that is removed. Hammer shaping is necessary for great tone: it is an ongoing maintenance procedure that never ends (i.e., the string marks will always come back if the piano is played).

I think it is also wise to choose a hammer that will "wear well." Hammers innately only get harder with use. Using a hammer that isn't a hard, hot pressed hammer to begin with, in my opinion, generally works better in heavier use situations.

sand only if there is enough "meat", if not just help the string marks to be less large and voice around, or even, voice only while keeping the imprints large, they will damp the high frequencies but will understand how to voice for more resiliency. needle around the crown to soften the external of the imprints , then a little low under 9 if it help,(do not if it does not) then lower under the crown to unpack hardened felt.

I like relatively frequent moderate filing.

Using some carbon paper to visualize better hammer contact in the end , on less important pianos it helps to gain time (cannot be cleaned well in the imprints)

the large and hard imprints are breaking strings and avoid the tone to be produced nicely.
Needling does the same as sanding, almost, in that case, the outer part is turned to be inconsistent, but will damp some hardness at the same time some partials are damped.

A single light stroke with 80 grit can help you before tuning.

From about middle C down to the lowest notes-a softer, lighter hammer produces a better sound when there are some definite string marks. This also produces a better range of tone color from the shift pedal. In the treble, once the grooves get deeper than the string diameter, a light shaping to reduce that helps tone. Treble hammers with grooves deeper than the string diameter sound worst when you are playing soft because the felt on the sides slightly damps the strings motion after the hammer has actually left the string.

What about if you need to go the other way? My partner's piano sounds too mellow, almost dull. The hammers have no grooves to speak of, but they are a very round shape. It's a Yamaha U2 upright. My piano is a larger U3 but is considerably brighter and she would like her piano to sound more like mine. The hammer felt feels more or less the same hardness as my hammers. I've tested this with needles. Should the hammers be given a more pointed, egg shaped profile to restore the higher partial content?

Shaping the hammers to reduce the mass will increase brightness and dynamics.

You could remove the same note hammer assemblies from both yours and your friends piano and weigh them on a sensitive gram scale. If yours are lighter, that tells you a lot.

If she decides to get some tone regulation done-you would do well to employ a technician who is skilled in hammer shaping to do the actual work.

Yamaha hammers usually get bright quickly when played so if it is now dull in the bass and middle-I would proceed carefully-because it will likely brighten up after 100 hours or so of playing. If the dullness is from about note 55to88-reducing the hammer mass will significantly improve tone.

Are you saying basic voicing (needling) before re-shaping would reduce amount of felt, helping preserve some of the life of the hammer? Does it make the felt raise in that area? I thought re-shaping then voicing was normal. I didn't know there was a benefit to needle first. I have a piano to do this week I will give this method a try.

Yes.

Yes.

Yes. I think it probably is, but this levels the hammer flat, then the voicing puffs certain areas backup again, and then the final shaping takes more off.

Beware: voicing directly down in the string marks will make a dramatic change, so please proceed with caution. The front portion of the hammer--at the string marks--is more sensitive to fff power/colour <----I recommend staying clear of this area. A better approach is to insert the needles at the una corda position, and angling under the string marks--which begins the una corda voicing procedure.

You need to reshape hammers before the action can be regulated properly, and then you can begin to work on voicing. Unless the grooves are minimized, you cannot set the let-off properly, and all the other measurements stem from that.

After that comes voicing. As with all voicing procedures, different techniques under different circumstances will give different results. You have to do it several times to begin to figure out what to do to get the results that you want.

Just as one should learn how to replace a shank or a string when one learns to tune pianos, one should learn to replace a set of hammers when one learns to deal with hammers by sanding and other voicing techniques. Eventually, you will come across a piano where your best efforts are beyond the condition of the piano. Sometimes you may cause this yourself, but even more often, you will run into pianos where there is not enough hammer felt to work with. Heavily worn hammers can have no felt on the top notes, or less obviously, can be worn down to the point where the felt is saturated with glue. There is nothing you can do except replace the hammer then, if you want good tone from the piano.

A443's advice about doing some needling prior to reshaping is good. But I wouldn't go much higher than note 55 with it. But if the hammers are like the old Steinway hammers-light and soft-I wouldn't do it at all.

If the hammers are like most of the heavier, dense felt hammers made since about 1965-A443's procedure may well result in a more even tone and a smoother shape.

The idea to wake up the felt, then layers are more easy to work with.