hammer-shank glue joint

[John Delacour]

At 4:17 pm -0400 24/7/07, Jon Page wrote:

>  >...what glue was used to install the hammers? I somehow suspect it 
>wasn't hot hide...
>
>I just reset about 75 notes on a grand which had new hammers
>installed with hot hide glue about 7 years ago.  I reglued them
>with Bolduc's Wood Glue which I use exclusively now for hammers
>since I have experienced hot hide failure when using distilled or tap
>water and premium glue crystals.

It's worked well enough for well-made pianos for 150 years and I 
would never use anything else.  Provided the hammer bore is correct 
and the shanks are properly knurled (and I don't mean the factory 
knurling) it is impossible for the hammer to work loose whatever glue 
is used. If it is still easy to adjust the angle of the hammer half a 
minute or so after the glue has been applied, then things are wrong. 
As the knurled shank re-expands with the moisture from the glue a 
point is quickly reached where the shank is a compression fit in the 
hammer-head and so it will remain when everything has set and dried 
out.  The only way to do hammers is fast.  If you rely on gap-filling 
properties of glue so that you have an eternity to move the hammer 
about until the glue sets, then that hammer is at risk of working 
loose.

JD