Front Rail Bushings

[Israel Stein]

At 11:55 AM 4/15/2007, David Skolnik wrote:

>Subject: Re: Front Rail Bushings
>Message: 1
>
>I'm confused or curious about a few of the responses to this question.
> From John Delacour come the information about the greater efficacy 
> of cold water in softening hide glue.  Can John explain why this 
> would be so?  If we are already using Dif and or alcohol as wetting 
> agents, there should be no reason to use hot water, if its only 
> purpose is to overcome surface tension.  Also, regarding Bill 
> Spurlock's sizing cauls, which I use, I wonder...I can see how they 
> would work if you want to reduce the mortise size to a uniform 
> width by wetting and glue sizing.  The fibres are expanded and then 
> fixed in their new dimension by the glue sizing.  However, if the 
> minimum amount of water is applied to wet the cloth and glue, 
> without over-saturating the wood, there would be minimal 
> dimensional change in the wood to begin with, thus making the cauls 
> superfluous?  If the wood IS saturated, the expansion would seem to 
> have already taken place by the time the bushings are removed, 
> especially if they are left for a number of hours, as some of the 
> posts suggest.  In that case, what is happening to the fibers as 
> the key drys?  Do they return to their original dimension or do 
> they remain expanded?  If you insert the sizing caul into the 
> wetted mortise after removing the bushing, what happens? Fibre 
> crushing?  If the caul is tight when wood is wet, and loose when 
> dry, how much control is there over the amount of shrinkage?  Is 
> there a glue sizing effect from residual glue?   Wouldn't it be 
> more consistent to allow the wood to expand (stabilize) and then go 
> through with a sized file when dry?
>
>If I dug up Spurlock's instructions, I'd probably want to unsend the 
>above.  Oh well.

David,

No need to regret your post. Here is the text about the mortise 
sizing cauls from Bill Spurlock's website. It covers all the 
questions raised above by you rather nicely, I think - from 
Spurlock's perspective, of course...

"These special cauls further improve the consistency of your bushing 
jobs by uniformly sizing the key mortises after removal of the old 
bushings. Just steam or soak out the bushings, insert a Sizing Caul 
into each mortise while the wood is still damp, and allow to dry. The 
mortises will then be very evenly sized with smooth, flat sides as 
shown below. Bushing stability will also be improved because the 
moisture-swollen wood will be compacted back to its original 
dimension, not left in a soft, expanded state."

If you want to see the picture, go to http://www.spurlocktools.com/id19.htm

Israel Stein


-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/pianotech.php/attachments/20070415/a396a6f0/attachment.html