Sizing Key Mortises (was inconsistent rail pins)

[Marcel Carey]

William,

>From my experience out here in Québec (cold & dry winters) the
keybushings will get tighter with humidity going down, not the opposite.
If you take measurements of the key width when humid and then when dry,
the dry key will be smaller than the wet one. So, the mortise will be
smaller as well. 

Marcel Carey, RPT
Sherbrooke, QC

> -----Message d'origine-----
> De : pianotech-bounces at ptg.org 
> [mailto:pianotech-bounces at ptg.org] De la part de William R. Monroe
> Envoyé : 11 septembre 2006 21:37
> À : Pianotech List
> Objet : 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
>