[CAUT] Key bottoms (was Re: key-easing pliers?)

[Fred Sturm]

On Jul 25, 2007, at 11:03 AM, Mark Cramer wrote:

> BTW, Bill's system is absolutely beautiful! I think we started with  
> the
> cauls in 95 (?) then added the heated-broach system (thank-you Master
> Wolfenden!) from Pianotek, and finally the mortise-sizing cauls,  
> whenever
> they became available.
>
> With the control over key-pin, mortice and cloth sizing, so little  
> variable
> remains. We record the cloth and heating broach size (as many of  
> you do)
> right on the key-board and in our records.

I couldn't agree with Mark more on how much better work is possible  
with current techniques, tools and materials. The fly in the ointment  
for me has been bottom holes. I have wished for years I could finish  
the bushing job, take the keys from the clamps, put them on the pins  
and be done (essentially, with very, very minor tweaking). But I find  
bottom holes slow this considerably, needing custom work on most keys  
after steaming out bushings. I've tried a lot of ideas, and none were  
quite satisfactory. But I have finally come up with a system I like,  
which takes me under 20 minutes, keys in clamps.

1) Check for holes that are too large, for sizing. Keys laid balance  
holes up, take a loose balance pin and insert in each hole. If a hole  
is loose enough the pin wants to fall in, wiggle the pin in the hole.  
If there is any chatter, chalk it and move on. Size the chalked holes  
with your favorite method.
2) Remove excess wood where present. I know, lots of "experts" have  
told us for years we should "never remove wood" here. They are wrong.  
We should never remove _too much_ wood here. Eric Shandall is now  
teaching use of parallel reamers for the purpose of easing too tight  
balance holes, in Steinway factory seminars. He uses .1470, .1475,  
and .1480 I believe, usually finding .1475 best. These are available  
on the web for maybe $10 each.
	I decided there was too much danger of taking too much wood using a  
reamer, and anyway I don't need yet more tools to keep track of, so I  
decided to try a drill bit instead. #26, from a #1 - #60 set, is . 
147. (If you feel paranoid about humidity swings and whatnot, use  
#27, .144". And, obviously, if the keypins are a different size,  
change accordingly). My technique is to push the bit into the hole by  
hand (no twisting) and pull back out. If the hole is particularly  
small, I repeat once or twice. To make it easier, I attach a stop  
collar to the bit (a pin vise would work). With a new, sharp bit, the  
flutes will cut pretty well. I find I mostly remove some splinters  
and some black sticky residue.
3) Heat size, using a home made caul in the keybushing iron setup  
(heat controlled soldering iron). Short piece of 1/4" brass, drill a  
hole with #27 bit (.144"), pound in a balance pin cut in half. Use it  
like ironing keybushings: about the same temperature and same time.  
No more than 1.5 seconds per hole. (The idea comes from Brian DeTar,  
who used something similar for sizing damper guide bushings. I have  
three similar things for that purpose, with #6, #7, and #8 bridge  
pins as the "irons. Works great!)
4) Even up key bottom thickness, using a balance hole reamer (idea of  
doing the whole set, as a common procedure, courtesy of Roger Jolly).  
Keys are held vertical, so that you can get at both sides at once.  
Insert through the top of the key, gauge how much should protrude  
through the bottom hole by eye and by feel (I guess you could make a  
stop gauge of some sort if you wanted to). Go through the whole set  
doing the same to each key. Sometimes this is a formality, sometimes  
it was really needed. I guess this step might go earlier in the  
process, before you even glue in key bushings, so chips can be easily  
knocked out.
5) Ease with balance hole easer, to make holes tapered. First feel  
holes with a loose balance pin. THey should be pretty consistent,  
with a little friction resistance. Find one with fairly high  
resistance. Insert the easer from the other side and ease. Feel with  
the pin. When you have it so that there is next to no friction, and  
no chatter at all, remember the feel and distance the easer is  
protruding through the bottom. Match that for every key. At first,  
you might check every key or so with a pin, until you feel confident.  
But this can be done quite precisely and easily, now that all holes  
are so consistent. If you like, make a stop gauge for more control  
and consistency, if you don't trust the feel of your hands and your  
eyesight.
	Now take the keys out of the clamps and install. Eureka! It works!  
Perfection at last!
	Next time for this set of keys, steps 2 and 4 can be omitted.

Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu





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