hammer hanging question

[Newton Hunt]

Dear Gordon,

Any measurement or specification is a guide only and is subject to
denial by the individual piano or, as they say, subject to change
without notice.  Your notice.

Before starting check the bedding of the keyframe and measure the
hammer centerpin height at each end of the action while sitting on a
flat surface and measure the string heights at each end of each
section.  The more accurate the measurements the better the bore of
the new hammers so write everything down carefully so you have a
record and send the specifications to your hammer provider or use them
to bore the hammers yourself.

Bore distances are critical to proper action function and proper tone.

The first thing to determine is, in replacing hammers in any piano, is
the action in it's proper location front to back.  Where the hammers
were in the first place is a non issue for you will want to locate the
action so it fits in the window provided by the fallboard, keyslip and
keyblocks.

Any variation in hammer location along the shank is of little
consequence at this point.

The keyframe should be moved to fit between the keyslip and fallboard
so there is an acceptable gap between the keys and the slip, no more
than 3/16" or so, and the fallboard so there is no great gap between
the ends of the sharps and the fallboard, about 3/16" or so.  If there
is a problem here determine if the fallboard is mislocated or the
sharps are too short and correct as needed or practical.

Mark the location of the keyframe on the keybed so you can relocate it
easily.

At this point some adjustments to the keyblock alignment plates or
keyframe alignment pins may be in order so the action can be located
perfectly to your preset consistently.

The purpose of all this work is so that the action 'looks' right,
performs properly and so that you have some adjustment potential later
if you need to do so.  The action can be pushed in only so far.

At this point check to see that the hammers at the top of the middle
section, the end of the agraffes, are spaced to the strings, the
shanks are perpendicular to the hammer rail, use a square, and the
shanks are parallel with the wippens and finally check that the shanks
are properly traveled.  If there is an outness here adjust the action
left or right to correct the situation.  EVERYTHING else devolves from
these adjustments.

It is a good idea to space the hammers to the strings, generally, so
you have an idea of where they might be going when the action is on
the bench.

Carefully check that the height of the centerpin of the new shanks are
exactly the same as the original or as specified by the factory. 
Differences here will effect bore distance and performance.

At this point shorten and install a new shank at both ends of each of
the top three sections.  Fit the respective hammers on their shanks
approximately where they should be, saliva is an excellent wood
sweller if the fit is too loose, and place the action in the piano and
move the frame in and out to determine where the best tone is relative
to the predetermined keyframe location.  If they do not agree move the
hammer in or out along the shank until the best tone and action
location perfectly agree, for each sample hammer.  Some minor
compromise in the lower sections is possible.

At this point you MUST determine if there will be a problem with the
hammers and backcheck picture.  You do not want the backchecks hitting
or interfering with the damper section or sostenuto rod or the heels
of the hammers interfering with the wippens, flange screws or with
wippen helper springs or threads if there are springs.  Compromises
may be required to make it all fit well with sufficient safety
margins.  Move the action first then the hammers.

If the final hammer location is somewhat indeterminate move the
action, or the hammer, so the hammer is hitting only two strings. 
This will help immensely.

Get the hammer located perfectly in terms of angle, travel, spacing.
verticality and shank length.

Now for the coop de gras, use thin CA to carefully glue the sample
hammers in place WITHOUT removing them from the shank.  First use some
accelerator on the shank side of the hammer to prevent dripping and
carefully allow CA to flow into the joint between hammer and shank. 
Too little is OK but too much is a mess.  There will rarely be a need
to break this glue joint.

Check location again.  CA takes four hours to reach it's full strength
so you have a narrow window of time to make a change.  If all is
perfect then you can begin to install the rest of the hammers.

The lower hammers can be glued on at an average of the lower two
samples in a straight line.  Their location is not as critical.

These are just the very beginning operations so don't think it is all
done.

Next comes,

Aligning, spacing, burning, spacing, traveling, spacing, burning,
spacing, traveling, spacing, spacing, spacing until it is as perfect
as possible; then do it again.  ALL else devolves from this  most time
consuming of all the procedures of regulation.  Wippens and backchecks
can now be aligned to the new shanks and hammers.

After regulation comes key weighing, voicing, tuning and re-regulation
and tuning and voicing and tuning and voicing.

These subjects have been covered in the past and will need to be cover
in the future, but not now.

Tighten the bench bolts and screws.

Now get busy.

		Newton