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

There is an optimal height for the whippens center. (relates to the common line between key center, whippen heel and whippen axis) letoff happen a little below the line of centers (whippen/hammer) to keep contact with the hammer until the end of the letoff (friction reduce from the begin to the end of the jack motion, but if it happen on the line of centers there is a loss of control, the hammer mass seem to disappear under the finger, not much appreciated, a too large shank position above horizontal can create that, as small hammers. Makes the action too easy and less controllable. Practically if you raise the back of the stack you gain some friction at letoff moment. (it can be good, if the knuckles are compressed, possibly)

So minimize shimming there, unless it does some good.

Remember that any small change in stack position means a complete regulation, letoff, drop, backchecks, springs, hammer travel distance.

The inclination of the action change a lot of things..

Rake angle influence the hammer center of gravity, hence the flex of the shank.
It is used to avoid blocking when let off is small, and the kind of electrical shock that result perceived in the keys.

The is more supple at 91-92 when playing strong, that with 90 and even less 89 deg.

The shank most often raise 2-3 mm above horizontal. (91°) better jack return And friction release at let off.

ALl hammer shanks are bending and releasing, so they generate a more or less pronounced motion from front to back.

The vertical or squareness of the hammer vs string's plane will depend of the force of the stroke.

The string's plane angle (from 0.5 to 2and even 3° in high treble) is not much taken in account. However the squareness to the strings plane is much sensitive in treble and high treble.

So I regularly have find actions where the rake was 91 x in mediums, to finally obtain 89-90 in the high treble.

This can as well be the result when using hammers all the same length , while the top sections of strings are lower generally, up to 3 mm in many actions. (idem for first basses unless the agrafes are corrected, the thickest strings are lower, hence a more close rake angle)

Interesting is that the close angle generate a better energy transmission at high volume , it is easy to play FFF on pianos that have 89°+ rake as Forster, may be Petrof.
The loss of intermediate nuances (more direct tone) have to be compensated by voicing., but the shank being stiffer, there are less possibilities.

I believe the bending motion of the shank allow to modify the tone, as the quality of the hammer/key acceleration can vary the impact condition more (less linear).

In fact that sensation of having the "hammer at the tip of the fingers" may include the shank springiness, that add to the resiliency of the key to give a "couple" of springs the pianist learn to take control on.

Most pianos have a bowing of the plate in the mediums, when working with hammers it is usual to evaluate the height and shape of the string's plane. Action being tolerant, up to 3 mm difference allow yet to use hammers all the same bore size, but most techs and the best factories bore the heads function of the strings height.

Vacuumed plates (in a lighter iron) are precise. Grey iron plates always warp a little.

I'll experiment with that. Thanks Olek.

changing the angle (adding 3 degrees +-)

the reamer is seen at the bottom (reamers for aluminium or plastic)

Front to back angle is checked too(here 92°)

a too large hole : I use a small shave of wood glued to close the hole enough (made with a small plane.)