Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Let-off buttons: not enough career for correct regulation.

The most precise way is to make small sticks with differnt lenghts (200-205 mm for basses , 196 to 200 for mediums and treble, but on old pianos string's height is often very tall as 205 to 215 in the mediums/treble.

A simpler way is to use those rules ('STanley, may be other brands) with a window :


It is important to measure at the good strike point , for instance around 45 mm from the agrafe for note 49 (A440) 2 mm form the capo for note 88, find a spot in front of the hammer center for note 1 but if they are worn or have been much filed you may want to make a small square with apiece of cardboard to evaluate where the hammer was touchin,g the strings originally .

(You also can measure the string's lenght", knowing the strike will be between 1/7 and 1/9 and that it is oftern at 1/8 lenght of the string )

WIth string's height less hammer center height you know the hammer bore more or less.

With string height less the height of the "ceiling" under the pin-block, you will know if the action allows for 47 mm hammer travel.

I will look at the pics now...

How are the whippen centering on the key capstan ? (in both directions, lateral and against the center of the whippen heel)

if the spread have compressed much the whippens will be toward the side of the most angled key (not well centered)

At first sight on the pics your spread is compressed , may be 1 or 2 mm. looks like the Schwander actions (while it may be another brand as "Union")as they where installed on, older Bechstein.

Are you sure the knuckle is 18 mm from the center ?

1 mmp spread more will yet do much, look at the edge of the whippen near the hammer rail, look at the position of the drop screw on the leather, probably you will see the drop screw imprint is a little moved from original.

ALso the jack end (tender ?) may be well centered under the letoff button.

Those are small hammers , small and light. not expensive hammers (tails/moldings Bechstein style ).

Anyway, with 18 mm dimension and larger spread, you will need more key dip unless you raise the hammers shanks (the touch will not be better then even if you will access to better repetition)

On those actions the whippen rail does not seem to be locked, when the screws untighten and the piano is played, the whippen rail move toward the pianist, and the touch get heavy.

The sharps may be above the white keys 2-3 mm when at full dip, but you may first test with 10.5 or 11 mm key dip on one key, regulate the sharp dip to have the same aftertouch and only now look at the sharp's height af full dip.

P.S. my mention of 11 mm key dip goes along with your 18 mm knuckle to center dimension, on a piano action, when one dimension is enlarged all the others follows.

The hammers are may be original, they could be in fact.

Good luck


PS I am may be wrong with the "spread" (or it is just 1 mm compressed) but the balance pins look a little too high in the mortise, your keyboard is possibly too low. may be just the aftertouch you miss

original hammer bore was 45 or 46 and 50 51 (plus or less eventual corrections if the string's plane is much crowned.

Very good dimensions

Looks like hammers where normally bored and have just wear.

Well,
This started when the let-off could not be regulated properly. When a hammer set has a lot of wear some of the measurements will not come up as they should. With a worn hammer set the let-off will be wide along with drop screw distance.

It seems that the let-off buttons have been adjusted all the way out and the let-off is still too wide. If you measure the amount of felt gone from the hammer set at the strike point, I bet this is the same amount of the let off being too wide……

Measure the felt at the side of one hammer, like the close up of that hammer in photo#10. Then measure the amount of felt from the front of the hammer to the wooden molding. If the front of the hammer had the same amount of felt as the side of the hammer then your let-off would be no problem…..

One way to solve some of the problems there would be to raise the key height a little bit. This will give you more key dip. But still your let-off will still be wider than normal.



The distance between the action and the pin block looks ok.



I was just thinking about the action stack…..Sometimes when shims are placed underneath the action stack this creates regulation problems with some of the measurements (tolerances). If the stack is inserted into the key frame then leave it there.

Hi Dan, I understood the opposite (no way to obtain letoff) ofcourse you are right if this is the other way, letoff may be regulated at the original shank's heigh more or less hence 4 mm from strings for instance (but the drop screw problem show something else IMHO

Hi Isaac,
I had to go back and read the original posting. I wasn’t sure but when I saw the condition of the hammer set, I went to the other thread on the main forum and found this…



The OP has another thread in the main forum about the same thing.

Another thread


With the hammer set in that condition the regulation will be variable especially the drop and let-off.

Well I will look at that later ...

Drop and letoff as you say depend of hammer wear, but when the whippen rail is not secured it happens it moves ,sometime one side only. Then a 1 mm difference in spread make trouble with springs and regulation.

That said it is not uncommon to have 1 mm difference in spread between basses and treble.

The action stak looks really classical schwander type. I suspect the knucke to center to be 17, visually and because it is 95% of the cases on European grands . Only Foerster used 18 mm , may be some Bluethner also. Alwys with enlarged key dip...

The whippen rail could have moved from original position. Have a look at the whippen in the first and second photos. The first is the lowest whippen and the second is the highest whippen. The drop screw seems forward on the highest whippen, but that could be the camera angle too.

The capstan seems in the correct place in both photos…..

You could be right looking at the photos of the last bass hammer and the top treble hammer. The bass shank is not quite level but this could also be from the hammer through let off and then caught by the back check while the top hammer did not go through the same thing.

I am thinking if he increases key height on those balance rail pins like you mentioned earlier, then that would increase key dip.

The Förster setup can be a little tricky the first couple of times. It looks like it could be 18mm as the hammer flanges are quite long. Most likely 17 as you mention.

Hi I was thinking of exactly the opposite situation with hammers blocking on strings, but my reasoning about spread is normal both ways.

I see the piano had 60mm hammer travel and 13 mm key dip, so it may be better now, but 13 mm ? the key frame is may be warped a lot. How where the sharps at full dip ? did they plunge under the white keys ?

Letoff can be left at 6 mm from strings due to the hammer wear for instance, as the higher you have to put the drop screw the most they are prone to touch the pinblock

At last the first and last notes should be regulated normally, but :

BEFORE any of those operations, I would take the stack out of the key frame, take all keys out, (clean the pins, lube, etc)

Then verify how the key frame is adjusted on the key bed

This have to be done with the stack screwed but without the keys .

(On those stacks if the front screw are not vertical they have to be screwed last).

It is very important to have a good contact under the balance rail (and front rail, and back rail but at last balance rail, so a paper sheet can lick under the balance rail at differnt places, then when the keys will be installed the regulation will be stable and without energy loss or "hard spots")

Many times we find the key frame warped high so no good contact (those pianos have no regulating glide bolts under the keyframe generally, if too much twisted, and hardened by time, a few judicious saw line can help to obtain a good contact.)

ONce you are sure of the spread (measure it ALSO in the middle of the action, at the beginning of all sections.

Yes the whippen looks in place when seen from the side, but this is not always centered on the capstan, there is quiet a margin, simply extreme positions may cause problems with the sharps, that raise more than the white keys generally.

in the treble, the spread looks a tad reduced, as in one pictture where the knuckles seem to be far on the whippen upper lever. Basically also the jack may center more or less under its button, that can help to understand if something have moved too.

You could raise the front rail or even raise the stack, but try to avoid creating friction and less acceleration between keyboard and action stack, so I would regulate with 5 6 or even 8 mm letoff as long as the touch is good .

The hammers are shot, visibly ; too much wear. They can be arranged but the tone will be limited the knuckles also are not in shape anymore so they produce certainly an "all or nothing" sensation .

The bigger problem that one can run into raising the action stack is that the drop screws will no longer fit under the pinblock. That is why I did not mention it.

It might be possible to get a bit less let-off by moving the wippen rail back a bit. But any adjustment like that can lead to other problems.

It is very easy to see if the hammers where bored at different lenghts in differnt sections : measure the tails.

To me they are bored correctly, but too much worn.

The tails have nothing to do with the bore distance.

But please BDB I am not arguing , the tails show the amount of bore left on the other side, all hammers being theorically the same lenght) this is just another check added ...

As hammers seem to be replaced (hole not full with the hammer shank) they are probably too small, and also possibly originally the rake was different (I have seen 94° rake on an old Bechstein for instance, due to an enormous overcentering, itself due to an enormous amount of crowning at the plate level.

Hopefully this is not so large generally, but most European hammers ar raked 91° (in the mediums, going toward 90 or less in the high treble)

it is less expensive to use hammers bored "standard" and all the same lenght, all depend if you have a high priority with jack to knuckle relation at letoff or no.

Bechstein 2.20 string height : 203.5 -204.5 // 195 195 195 194 194.5 194.5
hammer bore 53.5 54.5 //44.5 45 45 45 44 44.5 44.5
backchecks following with 64 to 66 height depending of the hammers

So visibly the plates are precise

On older models the diffence in height between note 88 and mediums is 3-4 mm often...

Too much overblow is a real problem then as the core of the knuckle bend with time, due to the force of the jack applied too much on the side of the knuckle.

I agree this is too much nitpicking for someone asking simple answers.

If this is a way to know the original key dip, I am full interested. What do "mortise" mean? (key button??) Can you explain me what must I check with that jauge?

This piano allows for 45mm.

Lateral looks OK, as you can see on pics.
I will check the second next time.

Yes. But I'll measure again!!

What does "raising the hammer shanks" means?

O.K. I am learning a lot!!!

But, I understand that aftertouch is related to key dip, not to key height at balance rail.
On this piano, balance rail (and the complete key frame)has no adjusting parts. Looks somewhat monolitic. And the balance rail is actually high. I had to put some cardboard below back rail cloth, because white key fronts had about 3mm more than standard heigth related to key slip. Also I had to add more than 2mm cardboard punchings on front pins to reduce the 13mm key dip to some normal dip.

Then I ask: Are all the action's adjustable parts there for compensate "normal" worn hammers, compressed felts, etc, or not?


I think I don't need to raise the keys; simply removing cardboard punchings from front pins would be enough to enlarge key dip. Am I right?

Just the opposite!!!


Key frame looks fine. The sharps didn't plunge. Perhaps they had some extra cardboard punchings on front rail pins. I don't remember now!!

There are lot of space between fully raised drops screws and pin block!!!

THANKS TO ALL OF YOU!!! Continued...

I was thinking and imagining one possibilitie I would like to share: What about covering knuckles with some thin leadher, to raise hammer tips to the adecuate heigth, without raising whippens out of range?

Hello!
I saw that the wippen flanges rail can be displaced several milimeters. Now, question is: how much?
Soon I will post more new info.
Thank you!

HELLO I dont understand well : many posters told you about the possibility it had moved from original.
Also If the shanks have really knuckle at 18 they ask for more spread than 112 113 generally. The first answer stated that, in fact.

Please let us know what you finally did. Best regards

Thank you Olek!
You are right. My last question were answered before!! So, I will try moving wippens rail one or two mm to enlarge spread, and to see what happens.
Now I will give you the results of my last visit to the piano (answering some questions you and others ask me time ago):

Strings to key bed:
Bass section: 211mm to 217mm (left to right)
Medium-treble section: 215mm to 212mm (L to R)

Hammer center pin to key bed:
Bass end: 162,5mm
Treble end: 160,5mm

Distance from pinblock to key bed: 174mm to 171mm (L to R)

Keys start moving dampers at 2 to 5mm from rest position.

Hammer to string angle, when hammer touches string: more than 90 degrees (hammer shank overcomes horizontal position)

Capstain centered to wippen: OK, both axis.

Drop screws old (or original) position signals. Not easy visible (perhaps, equal that current)

Spread, measured at middle of action: 113mm

Key frame warpped? No; it looks plane.

Serial Number: 22241

That's all! Keep in contact. The sooner posible I will go and I will try enlarging spread, key deep, and so on. (unless you propose to do another thing...)

Thanks a lot!

SO your hammers are really to short, also, they could be 50mm to 48 mm which are common dimensions on those style of pianos (and even some modern ones).

Are the heads 90° or 91° 92°or more ?

If the piano is worth it I would change the hammers.
Actually they are not impacting the strings correctly,nor on the best place probably.

I would change them.

If nothing possible of the sort, I would try to gain a little on the keyboard side, raising the back cloth and the balance (new damper regulation necessary) so to allow me to raise also the stack a few mm.
Depending of the hammer stroke you can also raise the hammer rail (change the distance between the centers in the vertical plane, it is admitted for 1-3 mm maximum, and not ideal for touch but possible, on a Flemming action).

Backchecks could be a little too low then but they are tall on those kind of action. You will have to change the backcheck angles if this solution works.

Be ready to regulate letoff/drop springs hammer stroke and jack position . samples are necessary.

With too short hammers the letoff is elusive anyway, the easiest way is to raise the front of the stack and it goe sin the good direction in regard of the hammer stroke.

Action must be pushed in the cavity for the strike line, if 5 mm miss on the hammer, the strike is moved a lot. older hammers are not shaped totally symmetrical for that reason.

Please verify the center to knuckle dimension.

ALl the best