On a grand, let-off buttons can't be adjusted for correct function. Let-off screws seems to be too long; buttons stops turning before achieving needed position.
Hammers and hammer knuckles are not too worn. Let-off button felts are not too thick. Hammers let-off now at about 10 mm from strings.
There are not independent let-off rail. Button screws are mounted on the main action rail, and buttons are "two cross holes" adjusting type.
I would like to know how could the piano come to this anomalous condition, and which is the best way to resolve the problem. I imagined re-place let-off screws deeper on action rail.

Are you another DYIER? "Do it yourselfver?" You'd better get a book on how to regulate a grand action or hire a good technician to do it for you. Sounds like you're going to mess things up pretty good the way you're going about it.

Chances are that the repetition springs are not bringing up the wippen and hammer to, the let-off position....

Focus on the first of these sentences, not the second.

If the piano hasn't been messed about with by someone that doesn't know what they are doing then set off should be able to be adjusted correctly. However if incorrect felts or parts have been used by an inexperienced person then it's anyones guess ... without seeing the instruments .... as to exactly what might be causing this problem.

I'am a new piano technician. Since five years ago I repare amd tune pianos on sur Argentina and Chile, where no other piano tuner ever cames. And piano owners apreciate my work and my constant effort on learning more and more.
Thanks.

Supose that another technician replaced the hammers, and that this was a bad job, or not the correct hammers. I think replacing let-off screws deeper on the actión is best solutión than to get involved in changing all hammers again, I'm ok?
Thank you, Whitindale!

Well...Lets see: when I beguin this piano calibration, hammer stroke were about 60mm and key deep about 13mm. And let-off 15 or 20 mm from strings. Obviusly, an inexperienced person were involved with this piano before me!!!
Now a have to diagnose accurately and to give the right solutión to this piano owner...
Thanks, Johnkie!

Have you tried with improvised buttons for one or two keys? I'd be concerned about geometry and pushing the action too far. Replacing the hammers could be better. I'd suggest posting the topic on the technician's forum with close up photos and details of the piano, budget, etc.

I am sure that if let-off buttons were shorter, problem would be solved. I have almost no dubt about this.
What means "pushing the action too far"?
I supose some time ago someone changed hammers, perhaps with its shanks and knuckles, and that some of this parts were not of the correct dimension. Also, I think perhaps they change the complete action (...?).
Is there any way to find the answer to this questions?
I will take photos if needed. But, first, let me please ask some questions: What is the maximum dimension from center of hammer shank and tip of the hammer? (maximum new hammer head size). What is the standard knuckle height? (if any...) (...and its distance from hammer center pin??) You see: if I can get those measures data, I'll be able to better understand the complete panorama. And perhaps, other forum members too...
Purchasing new hammers is not an easy task on that continent corner where we live!!
Thanks a lot!!!

You really should take this to the Technician's area on this board.

The answers to your questions depend on the make and model of the piano.

I'm still trying to work out what "not enough career" means. That's something mothers usually say to their children if they want them to enrol in medical or law school, isn't it?

The original action was designed to work within the limits of the let-off buttons. If you move the let-off buttons the action may have problems working outside its geometrical design limits.

The technicians forum is the right place to answer your questions.

Your explanation doesn't tell us what the problem really is. I'm assuming you are trying to bring the let-off closer since you said you have let-off at 10mm and you think the felt of the let-off button is too thick.
You are thinking that you can solve the problem by bringing the let off buttons closer to the action rail. Right?
Check the capstan, if they are too high, they can be bringing the whole assembly earlier to the let-off buttons.

However if incorrect felts or parts have been used by an inexperienced person then it's anyones guess

BDB, I'll post maker and model of the piano when I get it. I just ask for those items to the owner. Thanks!!!

Ando: I suposse that you and the others understand that english is not my language...
I mean that when I turn let-off buttons in order to get the standard 1,5mm let-off distance from string to hammer tip, they stop turning before I could manage it. There are not more space for the screw inside the button. (...not enough career!!!) Now, do you understand me? Thanks for your interest!

Withindale: I will post my question on the technicians forum right now. I just did not see that special forum before.

Kurtmen: I just said that felt on let-off buttons are not too thick, so all of you don't think this felt could cause the problem.
You say capstain perhaps are too high; but capstain are adjusted to calibrate hammer blow (or stroke) to 47mm from string, I'am wrong? THANKS!!

Not enough clearance.

It could be that the hammers are not bored long enough, that the knuckles are too small or flattened too much, or that other parts are the wrong size or position.

This is exactly what I think, after days and days studyng the all thing!!! Discarding that knuckles are too flattened, because they looks good, with no mayor indentations where the jack pushes.
More: how much has the knuckle to be out of dimension, to cause let-off to be no closer than 10 or 15 mm from string?
Thanks! Now I will post on technicians forum...

Pianosur, I hope you know that I was not making fun of your English. I would never do that and your English is fine anyway. It was just a light-hearted joke about musicians and how it's not considered a real career by many parents. I hope you aren't offended by what I said.

Apparently the original meaning of career back in the sixteenth century was a racecourse or a short gallop at tournament. In this piano the hammers' career towards the strings is cut short by the position of the let off buttons and whatever else.

In England some cars still career along the highway with gay abandon. One drove into me the other day.

All OT, but the topic's moved to the tech forum.

Thank you Ando! Now I feel better!!!
Friends: lets move to the Technician Forum. My post is already there...

Hello friends!
Here is all I have recovered:

Maker: H. Kriebel, Berlin
Action maker: Lexon, Berlin

Hammer bore (from bass to treble):
First section: 49 to 47mm
Second section : 41mm
Third section: 41 to 42mm
Fourth section: 42 to 45mm

Knuckles:
Height: 9,5/10mm
Distance to center pin: 18mm
Distance to hammer head: 112mm

Key ratio:
From top of key front to balance rail: 225mm
From balance rail to capstan tip: 115mm

Spread: 112/113mm

Look at the pictures.
Drop screws are also out of range. And is imposible to adjust drop to 3mm from string, for example. Repetition lever hits against hammer flange!! Aftertouch? Nothing! t
Remember: I adjusted key dip to 10mm and hammer blow to 45mm
I begin to think that complete action is to much far from strings...

Enjoy this piano-puzzle!!! THANKS to all you!!!

Failure with attachments. what to do?
I can´t apply text variations, neither

If you look at the FAQ section here, there is a post which explains how to upload pictures and imbed them here.

Pianosur, you suggest we move and then continue here.

Please decide which forum to use and show us some organised thinking. That way, all the info you are gaining will be in one place and more or less continuous.

I have some thoughts to add but I don't want to repeat information that might be on some other thread somewheres.

Sorrie. It was a fatal error!!! I´ll copy last post on Tech Forum.