MOLDED KEY TOPS

[Frank Cahill]

BSimon999@AOL.COM wrote:
> 
> 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



How long does it take to recover an entire set of keys?
-- 

Frank Cahill
Associate Member, Piano Technicians Guild
Northern Va