Sizing Key Mortises (was inconsistent rail pins)

[John M. Formsma]

I haven't noticed any problems the several times I've used the sizing cauls.
The keys usually are left to dry overnight. The cauls are generally tight
after the wood has dried. 

I think the goal is, as you said, a consistent size on all mortises.
Typically, after mortise sizing, I will use either the first or second
thinnest Renner or Pianotek felt.

JF

>-----Original Message-----
>From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On
>Behalf Of William R. Monroe
>Sent: Monday, September 11, 2006 8:37 PM
>To: Pianotech List
>Subject: Sizing Key Mortises (was inconsistent rail pins)
>
>Hi Terry, List,
>
>I use the Spurlock mortise sizing cauls every time.  I'm happy with the
>results, but I have always questioned how they function.  To my
>(oversimplified - at times) brain, I've always felt that pushing these
>cauls
>into nice moist keys and then letting them dry was missing something.
>Specifically, I would think that this would work well to size a moist key,
>but that the caul would size the key mortise while wet, form fitting the
>moist fibers.  Then, as the key dries, shrinkage would happen.  I would
>further speculate that the more moist the keys, the looser the end result
>would be.
>
>Perhaps I'm missing the boat, here, and the end result is less for the
>"exact" size of the caul, but for a consistent size on all the mortises,
>very close to the caul size, which is then made up for with different
>bushing cloth thicknesses.
>
>Thoughts?
>
>Regards,
>William R. Monroe
>
>
>> Assuming the keys are spruce or basswood or some other similar wood,
>you'd
>> be surprised at how much the key mortises can swell. Get things good and
>> wet > in there and with the Spurlock mortise sizing cauls I think you
>will
>> have very consistent results. I'm just guessing, but I would keep the old
>> bushings wet at least overnight to make sure the surrounding wood will
>> swell a little bit. Maybe you need to do a few hours on a wide mortise
>and
>> see how long it takes to loose the couple thou extra width - that's
>> assuming the mortises are irregular - perhaps they are not.
>>
>> Terry Farrell
>