To all who are interested in one more go around:
Here is the long awaited article which I promised. It is not the
last word on this subject, but it will perhaps give an idea or two
for your consideration.
If you will print the ascii art below and then connect
the dots, you will find an illustration of how the strings
form around the V-Bar. The longer the string is under tension
the closer will the string form around the V-Bar. Due to the
string stiffness, the string kinda' bends around the contact
point of the V-bar. If one massages the string gently for about
a half inch in front of the V-bar, the string will rise and more
nearly conform to the curvature of the V-Bar. It would be more
helpful to lift or massage on both sides of the V-bar at the
same time.
o
o \ /
\ /
o \ /
\ /
o O
o
o o o
The above illus. is slightly exxagerated to make the point about
the curvature on both side of the V-Bar so that one can see the
principle. One can massage both sides, in front of V-Bar and
behind V-bar to make the string conform more closely to the curva-
ture of the contact surface. In essence, this will raise the level
of the string where the hammer contacts it.
One of the things which cause one string to be higher than another
is during the stringing, one string may be pulled up higher than
another. The greater tension tends to make the string conform
more closely to the shape of the contact surface. If during a pitch
raise, one string is pulled up above pitch more than another, the
one with higher tension will end up higher than the other. eg, the
curvature of the string will have a smaller radius due to the
higher tension. This is why JIMRPT suggests tune, level, tune, level
etc.
If you jerk too hard on one string, then you have to do the same
for the other two. Make haste slowly. Use small increments of
change.
Sometimes during stringing in the Agraffe section, if one string
is pulled a half step or more above pitch compared to the neighbors,
a groove can be formed in the Agraffe hole. During the next
restringing, if the Agraffes are not changed, there will be a lot
of fighting of these uneven conditions, not to mention buzzes, etc.
The best way I know to check the string level is to make a very
straight 6" block of wood to which you glue a narrow strip of
bellyman's felt, the denser variety. With the Grand action removed,
you can hold the blocked felt against the underside of the strings,
then wedge the sustaining pedal down or the damper tray up and proceed
to pluck the strings. Now you will find that some Agraffes are not
perfectly aligned with their neighbors. Just use a slightly greater
pressure with the blocked felt. This technique eliminates the
problem of the unlevel hammers to start with. Get the strings level
first. Once you have leveled all the strings, Tune the piano again.
Then you can level strings again this same way.
Follow JIMRPT's suggestion in leveling the hammers by checking with
a Straightedge. About all I can add to this part is the tools you
can use to more easily shape the hammers so that there is minimum
leveling of hammers to do afterwards. One can gang file hammers.
When you do this, it is good to have the tails resting on a flat
straight board, not on the shanks. Be sure that there is no glue
drip on the bottom of a tail thus making that hammer stand up
higher. The simplest way to teach hammer filing is to use gang
filing with wide strips (approx. 4"). Yes, I know, the sides of the
angled hammers will not be filed the same amount, but you straighten
that up later with narrower strips (1/2" wide) to square up the
shoulders. Gang filing keeps the surface perfectly level, except
at the ends of a section where one might have a tendency to file
off more and thus make the hammers there not quite square on the
surface. Ease up a bit here. Check with a straightedge again. Now
for the shoulders. During Gang filing, one of the shoulders will be
filed more on the Bass side while on the back side of the hammer
the shoulder will be filed more on the treble side (this applies
only to the angled hammers). Watch to see that there is symmetry
maintained between the front and back sides of the hammer as far as
the sides are concerned which are filed the most. As you look down
upon the tops of the hammers, the angled hammers will look like
parallelograms instead of rectangles. You will need to make them
look like rectangles again by using the 1/2" strips and evenly take
down the high sides to conform with what you did with the gang
filing on the tighter sides.
After the hammers look good and are symmetrical again then you can
check for their level as far as the contact with the strings is
concerned. Use two strips of bushing cloth (the kind that is wider
and is used under the strings between the Agraffes and the Tuning
pins) and place this over the wippens with the knuckles resting
upon the strips. On some pianos, only one thickness may be sufficient.
The object here is to be able to press a key down (after you have
coaxed the hammers under the pinblock) and have the hammer block
against its strings lightly while you go through plucking and marking
the keys of any notes which have strings singing through or which
are not solidly blocked by the hammer. The advantage of this system
is that when you press the key down, the damper is also raised.
Yes, I know, you could hold down the pedal, but then you get a lot
of garbage you would rather not listen to at this time. I like to
make chalk marks on the top of the keystop rail indicating any
portions of a hammer which must be further filed.
For gentle filing, prepare two strips of the same grit paper which
you used in gang filing (medium grit?) which are 1/8" and 1/4" wide
respectively. If a hammer is high in the middle, use the 1/8" strip
to shoe-shine the center of the hammer. This way you maintain the
smooth curvature of the hammer. Do not overdo this because then
you will have to take down the two sides and this hammer will be
brighter than its neighbors. If the Bass or treble side of the
hammer is high, you can use either strip, the 1/8" will slip off
the side too easily. If the center and one side are too high, the
1/4" strip can take care of both string contacts at the same time.
Be very careful to not overdo any operation here because, the gang
filing helps provide even voicing throughout and if you overdo the
individual string filing, one hammer will end up smaller than its
neighbor and thus change the voicing.
You will need to do this last operation at least twice, probably
three times. So, you might as well get in a tuning or two. Then
after each tuning, there will be a little more string leveling to
do. But, it will go faster each time.
Some people have raised the question about the hammer string grooves
evening out the string level. It just doesn't seem to happen. I
just measured my strings with the felted block tonight, the strings
need to be leveled again even though the string grooves in the
hammers are indented a bit.
If one had not leveled the strings first and then found a hammer
which needed to be filed slightly in the center, if the shift pedal
is depressed, then the hammer would be out of level for the center
and right strings. You can see how important it is to have level
strings and level hammers.
Jim Coleman, Sr.
This PTG archive page provided courtesy of Moy Piano Service, LLC