Gang Filing 1-88

[Jim Coleman, Sr.]

Hi Ed:

There are negatives and positives regarding gang filing.

The negatives:
1. It looks cheap
2. It looks unprofessional
3. As the hammer wears, the grooves will offer more uneven strike points
     for the three strings of a unison.
4. Uneven stresses are left in the hammers.

The positives:
1. The hammer fitting to strings can be more even when done properly.
2. Hammer shaping goes much faster and is more consistent.

Gang filing can be done so that all the negatives are erased. This is quite
simple. In gang filing, two opposite shoulders are left high after the first
pass. A second pass can be made to even out the shoulders. The secret to
doing this is to carefully watch the thin shoulders to make sure that you
produce the shape you want. ie. during gang filing, on the first past on
a Grand pianos action, the back shoulder of the Bass side of the Bass 
hammers and the front shoulder of the treble side of the Bass hammers will
be shaved off more than their opposite sides of each hammer. During a second
pass, the resultant high shoulders can be gradually evenned up with the
other sides of their respective hammers. To do this operation efficiently,
the hammers tails should be resting on a flat thin board so that the
hammers are elevated to the strike point position during all filing. Care
should be exercised to not file too deeply in the treble or to allow a 
change in surface angle at the ends of each section.  When this is
done properly, one cannot tell whether the hammers were filed individually
or in groups. Any ironing of the treble hammers can more easily be done 
from this position.  This erases all of the negatives above.

It is important that before gang filing is done, the hammers must be inline
front to back. Otherwise, for a hammer which leans toward the back, more
material will be removed from the back side during the gang filing. So, a
little hammer burning needs to be done as a preliminary step. I'm sure that
someone will write back and say, what is hammer burning? Actually we don't
burn the hammers, we don't even burn the shanks (hopefully), but we must
apply heat to the shanks between the middle of the shanks and the hammer
to unwarp any hammers which may have warped out of their original factory
alignment. Care should be given to maintaining a smoothly graduated hammer
angle as well as maintaining front to back alignment. If a hammer is left
leaning toward the Bass, then more material will be removed from the
treble side of the hammer (if one then straightens up the hammer after gang
filing, the strikepoints will be wrong, so, straighten up the hammers 
first).

The disadvantage of individual hammer shaping is that until one develops
an advanced skill, one hammer may end up thinner than its neighbor. This
makes voicing more difficult.

In another life (when I worked for the Baldwin Piano Co.) I used to
demonstrate this at conventions all over the country.

The only danger I see in this approach is that it is too easy for a person
to get lazy and not do the second pass. He may feel that if he can't hear
the difference between a good job and a poor one, how can his customer hear
it? People with this attitude will get caught once in awhile because 
their customers (especially women) can often hear better than they can.
Improperly balanced hammers can cause jingles, buzzes etc.

Jim Coleman, Sr.


On Fri, 2 Oct 1998 musutton@alpha.nlu.edu wrote:

> Dear List,
>      Many of the pianos here have had their hammers gang filed straight across
> from #1 to #88. I've always shaped the angled hammers individually to keep
> the original shape. I would appreciate any comments on this.
>      Thank you.
> 
>     -Ed Sutton-
>      NLU
>