Hammer installation by hand (was Hammer Jigs)

[McNeilTom@aol.com]

To Vince, and List:

I don't think there's anything special about the way I install hammers, but
just in case there is, I'll describe.  This technique is for grands; I don't
know much about upright hammer hanging, although I've done my share in the
past.

It's nice to have a high workbench for this project (and some others, too).
 Try one about chest-high.  I like to work standing for installing hammers.
 It will be very valuable to have a block to raise the shanks to a horizontal
position; that way, the resulting hammer line will be perfect  __in striking
position__.

Install trials, last or second-to-last hammers for each section.  Use
originals or your best guess for position.  Then try the positions in the
piano for optimum tone.  If any need to be repositioned, do so; then test for
optimum tone again, to be sure.  When satisfied, proceed.

Ream hammers for a nice fit on shanks.  I like them just barely tight enough
to stay put on the shanks at the right position, yet easy to spin on the
shanks.  As I ream and fit, I leave the hammers on the shanks, not glued.

Begin with treble-most section.  (These are the easiest since they are bored
straight.  By the time you get to the tenor and bass, you will be "warmed up"
with the technique and it will be easy to accomodate the boring angles.)
 Glue on the hammers, one section at a time.  I use either yellow or hot
glue, with about equal preference for either. The upper action is on the
workbench, shanks pointing toward me.  I start at one end of the section,
installing the first hammer next to the already-glued trial.  A dab of glue
on the shank, another across the hammer hole's front face (side toward the
flange).  I blow a puff of breath through the hole, which explodes the glue
bubble into the hole, coating it evenly.  Put the hammer on the shank,
spinning it as it goes on, forming a nice glue collar and coating the shank
evenly at the same time.  By feel and sight, get the hammer close to its
ultimate position.  (Here, experience with the technique is helpful.  You
might be able to get something like half of the hammers exactly where they
want to be on the first try.)

Position the freshly glued hammer using a straight edge long enough to span
the section.  I test at three points: front shoulder, back shoulder, and the
tail in the area of backcheck contact.  When all three points are in line
with the trials, that's where it stays.  There is, of course, the matter of
having the hammer plumb.  I check this with a try-square against the
workbench top.  I sight across the blade of the square, checking each side of
the hammer (since by then the hammer is usually tapered), looking for an
equal angle on each side.  (Here again, experience might yield the correct
position on the first try.)  If the hammer needs to be rotated slightly, do
it and recheck with square and double-check position with straight edge.

With the first hammer (plus the trials) glued, I go to the other end of the
section and install the one next to the other trial.  I alternate from one
end of the section to the other, working toward the middle of the section.
 This accomplishes two things:  It gives the newly-glued hammer a few seconds
to set up without being disturbed by the process of installing its neighbor.
 And it cuts in half any tendency to accumulate error in positioning the
series of hammers in a section.  This should be a moot point, since there
should be no positioning error.  But this might be an added nicety for
novices with technique.

I should mention that I have a flourescent light fixture mounted on the wall
behind the workbench.  I can sight against this bright background for a
really good view of the alignment of the hammer with the square.  This light
contributes to the illumination of the whole work area, which helps the whole
operation.  This setup is helpful for some other operations as well,
especially travelling shanks.

When the angled hammers are installed, the straight edge is used to align the
corresponding  __edges__ of the three reference areas, instead of the
__surfaces__.  It is difficult to describe this, but if you set a straight
edge along the shoulders of the original hammers, you'll immediately see what
what we're looking for.  The tails of the new hammers will be a similar
situation to the shoulders, not square to the straight edge - although the
original tails will have been squared off.

I shape the tails after installing, using a 5-inch disc sander, 36-grit, in
my portable drill.
They end up perfectly even and parallel, nicely shaped, and with a very nice
checking surface.

I think that's about it.  Questions?

  -     Tom McNeil, RPT     -
Vermont Piano Restorations