MOLDED KEY TOPS

[Brian Lawson]

I once had a set of keys that had been sanded several times before that a
definate V had formed in the shape of the key, end on. I just removed the
old keytops, sanded the keys square and built up the key with available wood
to what would have been its original width - which matched the new plastic
keytops, then pretty much as Bill describes proceeded to shape the plastic
to the key.


Brian Lawson
IC PTG, MPT
Johannesburg, South Africa

----- Original Message -----
From: <BSimon999@AOL.COM>
To: <pianotech@ptg.org>
Sent: Friday, December 17, 1999 8:00 AM
Subject: Re: MOLDED KEY TOPS


>
> In a message dated 12/16/99 7:08:40 PM, tomnjan@bellsouth.net writes:
>
> << On trimming one of the newly installed key tops by
> hand using a rasp made of a carefully squared plank and attached
> sandpaper, I discovered that the key wood was not square, thus the key
> and top now displays a noticeable taper.>>
>
> For best work, Jigs and sandpaper just don't do a good job because they
sand
> the side of the key as well as the top. If you were only to lightly touch
the
> side of the key with sandpaper and "just clean them up to fresh wood",
taking
> off only the thickness of a postage stamp, that would be .005" to .006"
off
> of each side, seemingly trivial.  But -  times two sides of the
key, -equals
> perhaps .012" per key  - times 52 keys - equals  five-eighths of an inch
of
> gap width added to the set of keys.
>
> This is the minimum! The operations I have seen doing keys badly  just run
> the side of the key against a moving belt or disk, and since they sand,
then
> look, then sand, then look, they cannot see as they sand and they
frequently
> take .015" or .020" inches off each side. ( times two sides equals .040",
> times 52 keys equals TWO INCHES of gap added to whatever the keys already
> had. The keys look like  stand alone teeth in the mouth of an old man with
> receding gums.
>
> Don't sand, EVER, - because you always sand off wood and increase gap.
>
> The keys I do look fantastic, and I take nothing off the wood sides of the
> keys. I  trim off only  the top material.  I use a very fine 10 inch
single
> mill file.
>
> Buy a new file of top quality, never use it on anything but plastic key
tops
> and it will stay very sharp and cut very fast  forever. Pad the jaws of a
> good 4" vise with thick leather and lightly clamp the key side to be
trimmed
> facing up. ( Generally more stable if you actually clamp on the key top
> itself, just leaving 1/4"  stick above the jaws of the vise. ) Using a
handle
> on the tang,  fore and aft grip on the file and light pressure, just file
> down the plastic. You can see the amount of material removed with every
> stroke. You can see, and feel, that you have only perhaps .001" to .002"
left
> before the side of the key top is dead flat with the wood of the key, and
one
> last light lick with the file placed flat on the wood takes the key top
dead
> even with the side, and only removes the dirty fingerprints from the side
of
> the key, - and no wood at all.  You can easily feel the file going from a
> cutting action to a sliding condition. It is a "skill" thing.
>
> Then put the key upright in the vise, clamped farther back  with the
entire
> key top sticking well out and lightly radius the edges and corners of the
top
> with the same file.  Polish. Done.
>
> This actually goes fairly fast, and the result is superb.
>
> This method DOES NOT WORK with a poor quality or dull file. You will stand
> there cursing because it is taking waaaaay too long.
>
> One possible variant to this method is to use a medium mill file to take
the
> excess key top material off to about .006" to .010" remaining, then switch
to
> a fine file to finish.
>
> Happy Holidays,
>
> Bill Simon
> Phoenix