Backcheck repair

[Dave Nereson]

----- Original Message ----- 
From: <trc3j@juno.com>
To: <pianotech@ptg.org>
Sent: Saturday, March 27, 2004 1:41 PM
Subject: Backcheck repair


> I need to replace a couple of broken backchecks in an upright. Haven't
> done this before and my course doesn't really cover it adequately. Would
> appreciate a little procedure help before I dive in. I think I know what
> I am doing but it would be nice to get any appropriate 'heads up' ahead
> of time.
>
> Tim
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives
>

    Are the backcheck wires breaking off right where they enter the wippen?
(I assume so, since the only other "broken backchecks" I've seen are the
plastic ones from the early 50's that crack and crumble).  If so, it might
be a bad sign; usually if a few break, more will in the future.
    You can drill a hole next to the old stub and press a new backcheck in.
I grab the wire with a Vise-grips, then tap on the vise-grips to drive it
in.  (Wippen out of the action, in a vise.)  Really the head is supposed to
screw onto the wire, then the fluted end of the wire is supposed to be a
press-fit into the wippen, but I suppose you could tap the backcheck head
onto the wire, then screw the wire into the wippen also.  Either hold the
wippen with parallel pliers or put it in a vise or it will probably split.
    I've never found a decent method of removing the old stub, since it's
too small for an easy-out.  Sometimes you can drill up from the bottom, then
drive it out with a punch.  I've usually ended up digging and digging with
sharp objects 'til I can finally grab it and twist it out.  Then there's a
big ugly hole, but it can be filled with small dowels.  One suggestion I
heard of years ago is to drill a 7/32" hole sideways thru the wippen, right
where the backcheck wire will insert.  Then plug the hole with a short piece
of hammer shank.  Then drill the hole for the b.c. wire.  The hammer shank
dowel gives it new wood to grab.  The remaining vertical hole can be filled
with putty or glue, or just leave it if you're not concerned with looks.
    Procedures for replacing backchecks en masse have been covered in
Journal articles -- mainly on grand pianos -- but processes can be adapted
to uprights.  One is to use a drill press with a homemade plunger to push
the new backchecks into their holes.  A drill press vise can be used to hold
the wippens.
    And, of course, if the rest of the wippen, especially butt leathers and
butt felts, doesn't look so hot, you could just replace all the wippens.
        --David Nereson, RPT