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MMD > Archives > January 2001 > 2001.01.16 > 12Prev  Next

Loose Jack Flange Center Pin
By David A. Vanderhoofven

At 11:10 PM 1/15/01, Karl Ellison wrote:

> Howdy -- I've got pesky jack flange pins on a few notes, which like
> to sneak out sideways over a year's time and cause adjacent notes
> to either grace or parallel-play.  The action is only six years old.

A six-year-old piano should not have loose action centers unless the
piano was cheaply built, is heavily used and abused, or is in a poor
climate environment.

What type of piano do you have?  What brand name and model of piano do
you have?  A six-year-old piano would still be under warranty for
manufacturing defects.  But generally speaking, regulation issues are
not covered under warranty and repairs are the owner's responsibility.

> Is it acceptable to put a _tiny_ drop of glue (hot or white)
> on the pins side to prevent it from working it's way out again?

The action centers in a piano action act like hinges, allowing the
different parts to rotate.  There are action centers in the wippen
flanges, repetitions levers, jack flanges, hammer flanges, and damper

The center pins come in about 15 different sizes.  The center pin needs
to fit tightly in the wood so that the pin won't move from side to
side.  The other action part has a cloth bushing on each side that
allows the pin to turn smoothly and freely.  If there is too much
friction in the action center, the offending part will move sluggishly.
If there is too little friction in the action center, the offending
part will be loose and sloppy, causing action problems including
excessive hammer wear and loss of control in playing.

If the center pin is working its way out of the jack flange, the
acceptable repair is to repin the action center.  If several are loose,
it may be time to repin the whole set of jack flanges.

Please do not use glue to hold the end of the pin in place.  If you do,
the next piano technician who works on your piano will curse you.  Ask
me sometime about how I had to repin an entire studio sized piano
action and ended up scraping glue off of every single flange in the

Call a Registered Piano Technician to do the work for you, or at least
someone competent.

Below is a quick overview of repinning action centers.

Tools needed:

1.  A set of precision reamers.  (Get the set of reamers that is
sold from Schaff Piano Supply that was invented by Don Mannino.  Don't
waste time with the tapered reamers, rattail files or burnishers.)

2.  Sharp flush cut end nippers

3.  A tool for inserting and removing the center pins (This is
a plier-type tool with parallel action)

4.  An assortment of different sizes of center pins.

5.  A gram gauge for measuring the friction in the action center.
(This can be as cheap as the $8.00 gram gauge sold by the piano supply
houses, or as expensive as the $150.00 German made gram gauge I bought
from Pianotek supply.

6.  A digital micrometer that measures in .001"


1.  Remove the action from the piano

2.  Remove the wippen

3.  Use the action center tool to remove the center pin from the jack.
It is important that the center pin be pushed straight out of the part,
or the bushing can be damaged

4.  Choose a center pin that is large enough that it will fit tightly
in the jack.  If you can push the center pin through the hole using
your finger, the pin is not large enough.

5.  Measure this center pin with the micrometer.  Choose the
appropriate straight reamer and size the bushing in the jack flange
until the friction is correct.

6.  Use the sharp flush cut nippers and cut the center pin flush with
the flange.

7.  Reassemble the action, and reinstall the action.  8.  Play and

These are rudimentary instructions on repinning actions.  If you are
seriously interested in more detail, read Art Reblitz' book, or contact
the Piano Technicians Guild for more information.

But... PLEASE don't use glue.


David A. Vanderhoofven, Registered Piano Technician
Joplin, Missouri, USA

(Message sent Wed 17 Jan 2001, 00:58:44 GMT, from time zone GMT-0600.)

Key Words in Subject:  Center, Flange, Jack, Loose, Pin

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