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i just have had my tech replace all the key bushings.

according to danny boone's "regulating grand piano touch and tone", front key bushings "should allow only a perceptible sideways movement in the keys" and he considers sideways movement more than .012"(0.3mm) to be "excessive".

and i showed the tech this book and told him i wanted to have my bushings to be done that way.


now the tech brought back the keyframe with the keys fitted in, i found most of keys moved sideways more than "only perceptibly". in addition, he said he had black keys to have more sideways movement than white keys for some reason.

though i cant measure the amount of movement correctly since it is very tiny, at least black keys seem to have around 1mm of movement sideways.

he explained that recently techs at authorized steinway dealership in japan usually recommend making even more sideways movement.

so, what do you think?

i think what boone recommends is right.
in my opinion, key bushings should fit as snug as possible
as long as they dont causes unnecessary friction.

does any of you have any objections to boone's recommendations?
let me hear your thoughts.

As little side play as possible. All key pins and capstans should be polished and lubricated to minimize friction.

Are you an engineer?

I just ask because this is the kind of thing that engineers interested in DIY piano repair ask.

The thing to understand is that in pianos, to a large degree, function comes first and specs are an after-the-fact guide to what is likely to provide good function.

There are many considerations, including . . .
What time of year is it/what are humidity levels now and likely to be in 6 months?
What material is keypins? (Plated, anodized aluminum?)
Have the keypins been cleaned and/or lubricated?
What kind of bushing cloth has been used?
How rigid is the wood at the bushing mortise?
What is other action leverage, intertia and friction like?

The principle is that tighter tolerances do measurably increase friction and looser tolerances have more side-play -- creating sloppy touch sensation and possibly wear on the wippen heel.

In between "too little" and "too much" you have a space of some latitude that is "just right" -- or at least, "OK".

Personally, I wouldn't stress about it unless you are observing some issue as you play. The purpose of adjusting tolerances is to improve playability -- not to satisfy what somebody has written in a book, even if the book is generally on track.

it is about 0.4 mm for the front, but the lateral motion only is difficult to evaluate as there is also motion coming from the balance rail about 0.2 mm. under standard humidity.

leather bushing need more side play

+1

Greetings,
Let's just start with a digression, and hope it forms a basis for something...

There is an amazing amount of information that we receive through our five senses. I understand it to be on the order of nearly a terabyte per second. Whatever it is, It is far more than we can consciously process. To use the data, the body operates with thousands of micros running, all the time, while our sensory systems are communicating with each other, without us knowing it. We are rarely aware of the fluid in our inner ear, yet the loop circuitry between it and our entire muscular system provides us with constant equilibrium. It would take a mainframe just to handle that and that is one of many. A developed sense of touch is equally complicated, and feeds us vast amounts of information about the simplest things. The feel of the action is a combination of friction, mass, leverage, and springs. it all comes through the key, so the dynamic behavior of that key is critical and the bushings' contribution is significant.

When the pianist's hand touches a key, before the downward movement begins, there is already a sensory loop beginning, if not already complete. The location of the key is registered in relation to the others, and how definite this registration is depends on where the finger decides that key is located. "Where" can be blurred if the key has sideways movement when the finger touches it. The nervous system of the hand has to subconsciously decide where the middle of that wiggle is. Even though the key is effectively in the same place, if all of them are moving around laterally, the "feel" is one of vagueness. I had an artist tell me that one of our stage pianos felt like he was walking on a tightrope that wasn't tight. This piano wasn't sloppy, but the normal looseness of a working, university, piano, (concerts, warm-ups, accompaniment, Suzuki practice, etc...) was beyond his normal, and he much preferred our other, more coddled piano, with bushings pristine.

Inre tight tolerances creating friction, I think that once there is no compression of the felt by the pins, there is nothing to be gained by further slack. There is no need for there to be any clearance, but it is difficult for us to insure the necessary freedom for repetition without some perceptible movement. Front pins are not always straight, and binding can occur if the bushings are too deep, etc., so we have to have some freedom. It should not be visible, but it should be felt when taking a key and moving it side to side. By the time you can see the key move from a playing position, you have significant wear. Most felt will compact an additional five or six thousandths in the first 10 hours of playing, also, so a new key job needn't start out with any more than the least possible movement.
There are also reasons for resilient, close bushings that have to do with key behavior under staccato playing, (loose keys can bounce uncontrollably at higher speeds).

If you have a brand new bushing job,I don't think it should be loose enough to see keys moving sideways. Saying that a dealership in Japan is doing something as an explanation seems a bit of a stretch. If you can feel looseness in the key when you are playing, it sounds like you didn't get what you were seeking.
Regards,

good points, I may add that the way the key is holding on the balance pin is important in the way it is perceived.
A good adjusting of a good condition key shoe allow the "succion" of the key when the front is raised a little, but no motion when the back is raised.

The conical inside of some keys allows for a very long term fit and should not be worked with the usual oval tool, but precisely at a corner in the cone.

That is how we find very old Steiwnay keyboards that have the good fit at balance rail.

The thinner shoes cannot be managed as well.

As a pianist, I find this remark to be disturbing. Apparently the OP had work done to correct a problem, or he wouldn't have had the action serviced in the first place. The result of the service was not to done his satisfaction and is merely asking "is this normal?" It is the reason that he submitted his/her question to this forum. His source of reference is irrelevant, as his fingers told him the job had not been well executed and was then given excuses.

A proficient pianist immediately senses a sloppy action. The whys and wherefores of the reasons for the problem should not be the concern of the pianist. That is the job of the technician. If the customer then gets a run-a-round, and tries to obtain additional information as justification for any complaints, that is to be commended. Seeking information and understanding, from multiple sources, does not indicate that the person is a mechanical engineer or a DIYer. It indicates a pianist who wants his/her piano to perform at its maximum capability and is trying to understand why it is not, and obtain validation for apparent displeasure concerning the work which has been performed.

Boone's book is excellent as a general guide but you must remember that it concentrates and generally is addressing quality Steinway pianos for the most part. There are some small differences between manufacturing tolerances on the key sizes and the gaps between them, and more importantly, the quality of key bushing cloths. These two things combined may change the "specs" slightly on different brands of pianos. A poor choice in quality of key bushing cloth for eg., will render too much friction if you start to tighten up the tolerance to the level which a high quality piano can be set.

One of the hardest things to do is to develop a consistant way to test lateral movement key to key. I've seen more ways to do this from techs than can be written here but most all use some kind of sideways finger pressure. Myself, I use a dial faced finger type spring gage. I put a small piece of tacky putty on the tip so it gets grip on the key. It looks similar to this, but has a dial indicater as the meter...

Outside of specs, I simply ease up the bushings just enough that friction does not become too heavy or erratic and accept the movement which that combination of pin and cloth gives me, and this will vary a bit amongst pianos. No key should ever move more than 25% of the overall gap between it, and this is very close to Boone's recommendation in most pianos.

My point exactly: If it doesn't feel good then it isn't good. Period. (Which was the thrust of my response)

But OP wasn't saying that, was he? He was citing measurements and specifications -- which, as we both apparently agree -- are subsidiary to the actual feel.

Greetings,
Inre the original op remarks, if a key, black or white, has 1 mm of movement in the bushings, that is way too much for a new job. .012", as per Danny Boone's recommendation, is about maximum for a beginning spec. I have also, in over three decades, never heard or seen any reason that black keys should have more free play than whites.
Regards,

I agree that we have complex sensory capabilities that provide huge amounts of useful information about what we are doing. That's why I have said that if it doesn't feel right, then it isn't.

I used to believe the same thing you expressed about if the felt isn't pinching the keypin then it should be OK. It's not. There IS measurable friction with the kind of setup you describe with sideplay 'feelable' but not visible. A bit more side play that is also visible will reduce friction. It may or may not matter much in a given action setup.

Hello Pierrot!

Key bushing tolerances are usually said to be .007" at spec. What does this tolerance mean?

It's just an important way to communicate that the keys should be firmly held in position by the bushings at the balance rail and front pin. But there's a second, more important function that the front bushings play in an action: the damping mechanism for the keys.

Proper key regulation may vary several thousandths from .007" on different keys to maintain proper dampening friction at the pin. When bushing quality is not at 100%, tradeoffs may need to be made in side-to-side key play to achieve the more important characteristic of damping friction.

The keys should fall back on a noiseless air cushion if they are regulated just right. But the amount of this has to be regulated to other characteristics in the action: most importantly, hammer weight and leverage ratio.



This may be true because reducing front pin friction is usually the fastest way to decrease downweight on an action. Steinways are notoriously heavy and the Japanese techs may want to be making them respond more like Yamahas (or pre-compensating for humidity expansion).

Good luck and godspeed.

Really? A noiseless air cushion? That's a new one to me!

the only way to use an air cushion is to use polyurethane foam for the front punching, as does a friend to fight impact noise.

I can imagine the sealed mortise, with a little valve yo regulate the harndness , but not.

Yes, that's what I was thinking Isaac. There are too many points of leakage for these bushes to support "air-cushions".

I forget how hyper-critical these forums can be at a slight mismanagement of words. 'Air cushion' was a descriptive device as to the feeling of well regulated keys.

You are right, Ando - what is happening in the key is just the right amount of felt contact with the front pin that gives that feel of cushioned dampening.

Thanks for the clarification. I certainly wasn't being snide in my reply - I honestly thought you meant it literally. No offence intended.

Hello pierrot,
Possibly, the bushing felts were changed and you got whatever the new felt/cloth, glue, minus (but hopefully not) whatever wood fiber came off in the change out. How do the key spacings look? Do the keys ever touch with the excess side-to-side motion? Do the keys move enough so that the spacing of the keys may look different from time to time, depending on how you played the keys last?

I would wonder what the pros would recommend as to mitigation if pierrot decides to request reduction in side to side motion. My vague recollection Reblitz says to swell the wood if there is too much play and not turn the metal front pins because that causes excess localized wear on the felt/cloth bushings, but I think most techs turn the metal pins.

Regards-

There is a good reason why front key pins are designed in a certain way. Turning these to reduce "play" is not a good idea.