A question about hammer construction

[Frank Emerson]

Underfelt serves a purpose in the manufacture of the hammers.  The hammer moldings are first cut into individual hammer moldings, then taped and clamp back together as a set.  The tapered felt remains in full-set sheets.  In the hammer press. the moldings, as a set are pressed into the felt, and side cauls move in from each side to complete the pressure on the full perimeter of the felt.  After pressing, the individual hammers are separated by working an automated knife between the moldings to slice through the felt.  With softer wood moldings, like mahogany, there is a risk of cracking or even shattering the moldings in the pressing operation.  If the press is not set up properly, there is the risk of similar damage to walnut or maple moldings.  By applying the under felt in one pressing, and the outer felt in a second pressing, this risk is reduced.  In each pressing the felt is much thinner and more compliant.  Beside the risk of damaging the moldings, there is also risk of damage to the felt, when it is pressed at full thickness in one pressing, with no under felt.  The obvious advantage to a single pressing is that it is cheaper to make, as long as the damaged rejects can be kept to a minimum.  The smaller the hammer, and the harder the wood of the molding, the more practical single pressing becomes.  The end result has less to do with the quality of the hammer than the practicality for production.

Frank Emerson
piano guru at earthlink.net


----- Original Message ----- 
From: William R. Mon roe 
To: Piano tech List
Sent: 3/17/2007 2:15:10 AM 
Subject: Re: A question about hammer construction


: Is that colored section actually a second layer? (We could not tell by feeling it.)
: Is that colored section, or second layer, actually functionally different than the rest of the hammer? 
: In other words, does it actually do more than merely act as an identifier for the characteristics of that hammer?
-- Geoffrey Dykes
-- Cassock. Los Angeles
SNIP
Geoffrey,

In many (most) cases, the colored layer is indeed a separate layer, the Underfelt.  In some cases, it is simply dyed to make it look like it is.

When it is a separate layer, it is still, in most cases just a dyed felt, with no stiffening agent added.  In some cases (S&S) a stiffening agent is still added, thus making the hammer Underfelt much less resilient.  Of course, now the entire S&S hammer is soaked in lacquer as well, but that's another topic.

The presence of two colors does NOT indicate higher or lower quality.  Some very high quality hammers are solid white, some (most, if not all) crap hammers have a dyed "layer."

William R. Mon roe
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