Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Changing angle on prebored hammerheads

I need some advice.
What is the easiest way, and the best way to hang a set of hammers that are prebored at a different angle than what fits the strings of the piano? The difference is not huge. The bore length fits. I know it's possible to plug and rebore, but is it possible to enlarge the hole, make shank thinner at end, or both, to correct angle when glueing? I suspect it won't , as it would be too weak if the tip of the shank is not a tight fit in the hammer, but I'd like to hear from some experienced technicians. If by any chance there is a way, any special technique, or glue? I'd hope hide glue works, as it allows unglueing? This is a learning project, on my own project piano. Thanks.

if youuse new Renner shanks they are conical, so you may be able to modify more the angle without wooble.

you need a reamer in the drill press, and I would add a boring jig adapted so the reamer can pass thru.

no loss of front-back angle (rake) then, and bettercontrol on the final angle. It can be done free hand of course, but you need a good helicoidal reamer. 5>6mm (for aluminium, plastic, etc)

Olek, thanks, I am using the old shanks, cause I want to experiment before trying my first new hammer hanging job. I would elongate the hole at one side, and not all the way to the back? Difficult to visualize. So you mean glueing with normal hide glue would be strong enough?

mix skin and bone glue so the glue is a little supple , thick and does not drip much.

If it is a vertical , buy an adapted hammer set (it can be approaching angles) For a grand only you can ream, as the initial boring is too small and must be adjusted to the shanks individually before gluing.

then the reaming pass thru of course. You certainly can obtain 2-3 degrees without problem.

If the old glue was vynil glue or similar, I would use the same kind. Hide glue need to go within the wood to be efficient.

It was bone glue, dark brown, very easy to unglue with moisture. Old, used hammers, so not prebored, but already bored. It's a grand. Eventually I'll buy a new set, but I like the sound, and its great for practicing voicing without risk of ruining anything of value. I filed half of them already, I do 10-20 everyday, as I do it outdoors, and it's still cold. Also not as boring. The hammers are too flat on top, so I have to reduce quite a lot to obtain the right shape. Thanks for the advice, Olek.

WHat I would say is that it is not really the good idea to mount old hammers, the felt have no much tension available, you cannot train for voicing on those (only needle at the top a little) generally.after filing you are on a hard felt that is not sustained from the sides, and you probably cannot create a suspension, unless they are impregnated and needled again.

It should be more rewarding to mount a new set.


Plus the tails have been shaped yet. for another piano.
yes it may have been hide glue.

Up to a point, you can use a shank knurler to give a little wiggle room. You have to hold the hammer in place while it sets.

Is this a grand piano or a vertical? Which angle is wrong? If it is not exactly the same as the original, it probably does not matter. Hammers are never an exact match for the original, particularly since the originals are usually not exactly the same size as they were originally.

Olek, true, I know, but it's a lot I can learn, I'm trying to go through procedures so I am better equipped when I do buy new hammers. Funny thing, it checks perfectly. No need to do anything else but have backchecks a hair backwards.
BDB, it's a grand, and it's the alignment to the strings, it needs to have bass hammers some degrees more to the left, and tenors to the right.
My biggest concern was that it should be a very tight fit. I need to keep the hammers in place until glue sets, but once hardened, it will hold, I understand. Thanks.
Probably easier for me to just reduce the shank just bit, and see if it's enough. If not, ream the hole a little too.

Some play is needed for alignment. Yes, realign if the hammer drifts during drying.

Why not just angle the hammerheads a bit in the direction you want, and remate?

How much off are we talking? Are they hitting the neighbouring strings?

No, they don't hit any neighbouring strings, and I think it's just a few degrees, but I have to measure really, I'm not good with determining that visually.
Angle the hammerheads, how do I do that? Heat? What will be changing shape, the shank?

before gluing the hammer is reamed conically, you can change a little the angle.

you may be disturbed by the different angle because ou want to use original as models.

I suggest you measure all the original angles in degrees or Gon, plus the back/front angle if any (often 91°) . measure also the exact location of the strike by triangulation from the drop screw (for instance 145 mm from the drop screw to the tip)

So even if the samples you keep are notidentical you will preserve the strike point.

Think that if the hammer issmaller the strikes is moved a little toward you, and the hammer does not hit the strings as vertically as wished. SO it may be a good idea to make samples at strike height, reproducing the original strike at that heigh and not at rest. It is sensitive for high treble hammers, the action can be pushed back a little in the cavity but it is better to glue at the good location.

Anyway the high treble and treble strike are located by listening. There are some "standard locations too" in the German method, the strike is progressive from A49 to C 88, and have a different progression toward the basses (%of string length )

the best gluing is done with the hammer "at rest" on a small stick, so you can eyeball the hammer motion of each new hammer glued.

Gigs can be used too (to line the inside of tails) but the surprise is at the end of the job.(because the tails do not have the same "thickness" with angled hammers and with the 0° ones)

The orientation of the hammer in the vertical plane is important, energy wise.

Sometime a simple shimming of the action stack to get a better vertical position gives a lot of cleanness to the attack tone.

Gluing hammers is really something you begin to be good at after sometime.

How well do the hammers fit on the shanks? This all may be moot if the hammers are loose on the shanks. In any case, the angle to the string is not critical. If it is too great, you may have trouble getting the hammers to avoid each other.

If you are expecting to install hammers by taking out alternate hammers and matching the new ones to the old, that does not work too well. Better to line up the strike points and angles of the end hammers of each section, and then work from one end of the section to the other. Then the bore angle does not make much of a difference, because you are comparing it to other new hammers, rather than to old hammers which may not be the same.

Afterwards, you may need to taper the tails of the bass hammers so they do not hit each other.

working from both sides at once help to avoid mistakes (bowing, slight change all along to the last sample)

I can see why! Thank you Olek for the details, some of which I remember from a course I attended before, where hanging hammers was a part of it. But trying to actually do that by yourself is another matter. I will go by small steps. I'll definitely go by measuring and not by fitting to an original, as it can be misleading in this situation. Good thing I can undo easily with hide glue. This is going to be very exciting. I also will take the time to check for best striking point the long way, as I cannot trust the originals either. I'm working very slowly, as there is no deadline. I understand very well what you say about vertical position. That's the most difficult part, I think. Was it 91 degrees overall, or only in the high treble? The rest, 90? Or 91 generally and 90 in high treble?

After unglueing one hammer, I could see the shank is quite lose.

I see what you mean, so I'll dry fit the first and last hammer in the section, very tight, check them carefully, then glue the rest one by one. I could dry fit all maybe, so I can see if the progression is smooth. If I really take the time to tighten the dry fit properly, I can gently install the whole bass section and check it in the piano.

The hammers work the way they are, and the change would be so slight, there is a big chance they will not hit each other. The way they are now, they don't clear the left string fully. It's more visually, muting the center and right string shows that left string is not really hit, but vibrates simpathetically a little.
After glueing in a slightly new angle, the tail will not be square to the backchecks, so I have to correct that, right? By filing, or changing backcheck angle?

The hammers have to hit all three strings evenly. You cannot voice them properly unless they do.

Tails are usually only partially shaped, and need final shaping once they are mounted. I do it with a belt sander.

There is a lot involved in replacing hammers. You cannot skimp on it. I have had to redo bad hammer jobs several times.

Of course, I'll need to see the strings get muted equally when pressed to the strings. I like to raise let-off until it starts to block, rather then using felt under knuckles. It won't be a good job from the beginning, but I'll learn and get it better.

jinorden, I only recently hung a set of pre-bored hammers. There were differences in both the angle the the hammer makes aligning with the strings, and the angle the hammers make with the shanks. The bores were also slightly narrow so I lightly trimmed the shank ends.

It does not really matter if the hammers angle to the strings slightly differently to the originals. The back checks will need to be readjusted though. Also, it may be necessary to reshape the tails, and trim some felt of the sides, to prevent adjacent hammers contacting.

The hammer angle with the shank (rake) may cause some issues. In my case, in order to preserve the strike point, the originals shanks protruded through the hammer cores and required trimming. If this works the other way then there may not be enough shank length.

Glue-wise, I experimented with different glues. I tried hot hide glue, CA glue and Gorilla glue in different sections. I prefer to use Gorilla glue as it allows a comfortable working time, and it fills gaps as it expands. Excess expansion residue is easily trimmed. It will also loosen again if necessary by heating with a hair iron.

If this link works, here is a Facebook photo album of my job.

Thanks Chris, I tried the link, it works. I looked at the pictures, looks fantastic. The wood jig you use is something I'll try to imitate. My hammers being used, won't be easy to align, but I can try. I think the shanks are too short by 1-2 mm, by elevating the action frame with a cardboard piece, the sound gets better, fuller and rounder. Without the cardboard it is slightly more nasal. Very little though. I want to try having the hammer strike even farther, to be sure the tone doesn't improve even more, but the backcheck is in the way. Would you temporarily bend it away a little, to have space for a too long shank? It would be very little, of course. I cannot move the action more into the cavity.
Also, the rake changes the strike point, doesn't it? But I shouldn't go over a certain amount, or there is loss of energy, as Olek was saying, if I understood correctly.

My conclusion is that used hammers are much harder to change on the same shanks to fit another piano. Also the correct strike point is 1 mm farther in, but the shanks are too short. I discovered that burning the shanks in the right direction, shimming so the whole keyboard action moves some mm to the right, and shimming the stack a bit higher, is giving much better results. I am grateful for all the help and advice.
Just one question, to move hammer strike back, should shim the stack front, back, or both? How little increments? I think only front, but just to make sure I am not mistaken. I know I have to make sure drop screws clear the stretcher. Thanks.