Kawai heavy action (long)

[Jim Harvey]

Hello Fred,

Friday, March 26, 2004, 12:25:37 PM, you wrote:

FS> Yo Jim,
FS> 	I would love to read your two cents worth on the subject of "repairing
FS> existing knuckles."
FS> Thanks,

Sure Fred! Glad to read that you have more details and are homing in
on this job.

First, to those in support of bolstering. I don't use bolstering in
this particular case, because essentially there is nothing wrong with
either the size or the geometry of the knuckles. There's just too much
leather wrapping the core material, and by the time one bolsters
enough to take up the gap, other conditions could be created as a
result -- out-of-round; lumpy; bolster material slipping/walking, etc.
Besides, either method requires about the same amount of time and
energy.

Ditto shrinking, mentioned as untried by myself, then mentioned again
by Isaac. To be politically incorrect, this is the equivalent of the
"Indian torture treatment". It may work for finite adjustments, but
I'm not sure about gross tightening of the buckskin. I've just never
tried it to verify results.

METHOD:

Two cents worth is all I have on this, because, while I've done this
routine several times (across brand names), the last time was quite a
while ago. Since it's done so infrequently, I never generated a
detailed procedure for it. The following is from memory, but should be
in the ballpark.

TOOLS/MATERIALS:

Hot hide glue
(same consistency as for hammer-hanging; i.e., same as a "good head
cold")

Glue applicator
(wooden coffee stirrer/equivalent - not popsicle stick)

Single-edge razor blade
(preferred to razor knife for LACK of flexibility)

Clamps (I have some cheap metal clamps that LOOK exactly like
spring-type key clamps. They are smaller and lighter in weight, and
have less squeeze, but provide the broad flat clamp faces and enough
pressure at the moment of gluing, while featuring an open area that
does not compress/distort the knuckle itself. It would be great if the
original size/shape of clothespins were different - a little shaping
would make them ideal.

PROCEDURE:

1. For speed and efficiency, this is done with shanks/flanges still on
the rail. Note: thinking that there is less shearing tendencies on
jack return than during escape, I prefer to make incisions on the
flange side of the knuckle. This coincidentally makes the repair all
but invisible. If clearances do not permit, this is not a critical
thing, so working from the hammer side also works and yields a clean
job. Removing the entire hammer rail (where possible) often helps in
either case, otherwise the stack is rolled over with hammers either
hanging off the edge of the bench, otherwise supported. There is
little trauma to action centers in this procedure.

Do a couple samples one-off to get a feel of things, before committing
to cutting all the leathers en masse. (below)

AFTER SAMPLES
Obviously, leaving shanks/flanges in place means you'll be getting in
your own work path; also known as painting yourself into a corner.
With the work time of hot glue, and since the knuckles are not being
'worked' or stressed during the job, working on every third or fourth
knuckle is okay (depending on clamp size). This means that just a
half dozen or so clamps used in rotation will suffice.

2. Make incision into leather with the razor blade parallel to the
knuckle face, but with the back of the blade on a diagonal (angled
towards you instead of toward the flange (easier than straight cut).
The ideal spot is slightly above where existing leather is glued,
leaving a trace amount of original leather along with factory glue.
Note: too close to the core and the leather won't separate -- try to
determine the top EDGE of the original glue line. The glue most always
has wicked somewhat into the knuckle bolster cloth. Running a needle
between bolster cloth and knuckle leather helps arrive the appropriate
average cut line. A straight-edge and/or elevation guide may be
appropriate for speed and accuracy.

3. Cut ALL remaining knuckle leathers to establish rhythm, speed, and
consistency. Also since we're doing every 'x' knuckle, the loose flaps
provide excellent indicators of which knuckles still need to be glued.

4. Place a smear of hot glue on the previously cut stub of buckskin
and core. The dipped end of the coffee stirrer should provide exactly
the right amount of glue.

5. Holding the spring-clamp open, place one foot of the clamp on the
opposite (uncut) end of leather. 'Roll' the opposite clamp foot across
the surface of the leather, ending in the freshly glued area. Watch
for side to side symmetry on the leather, but disregard any exposed
leather showing outside the clamp. Note: this rolling action
practically assures consistency. Therefore no additional pre-guessing
or stretching is required.

6. Once all knuckles are done and glue has cured, remove excess
leather with razor blade. (the objective is to slice the excess
leather into the old stub of leather, again on a diagonal. This helps
provide more surface area for glue, along with feathering the newly
glued portion to the original stub for a seamless look. You'll be able
to 'feel' the layering effect through the razor blade when the
appropriate cut depth has been reached.

7. Any residual leather 'fluff' can be clipped with flush-cutting c.p.
nippers, including any accidents (any that the edges went beyond the
core material.

Hope this at least hits the high spots! If on reading this it is felt
I left out something or was unclear, please advise.

BTW, Fred, your estimated time is in the ballpark for this portion of
the work.


-- 
Regards,
 Jim                            mailto:harvey@greenwood.net