Bridge attachment

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: BobDavis88@aol.com=20
  To: pianotech@ptg.org=20
  Sent: July 25, 2003 1:40 PM
  Subject: Bridge attachment


  There are obviously several ways to clamp a bridge to a new soundboard =
while gluing - pneumatic press, go-bars, screws with their holes later =
filled with dowels.=20

  Suppose one is using screws. I have heard several people say they =
don't like to drill through ribs. The old Steinways had a combination of =
screws through every rib which were then dowelled, large dowels  up into =
the areas between the feet of a footed bridge, and screws through =
soundboard buttons in the high treble which were just left in place. Is =
there a better way, if one is using screws? It seems like drilling =
through ribs weaken the ribs, a hardwood dowel through a thin softwood =
soundboard between the ribs could break free later and buzz, and a screw =
left in place through a soundboard button could loosen and buzz, =
especially since many are inaccessible.
Drilling through the rib does weaken it. This is not a problem if the =
soundboard is compression-crowned. In this case the rib is not =
supporting crown, but resisting it. It needs to be some flexible.=20

In the case of a rib-crowned soundboard system the rib is a structural =
member. It is not a good idea to do anything that would weaken the rib =
right at the point where you are putting the most stress on it--directly =
under the bridge.=20

Most of those who use screws and buttons to attach bridges put them in =
between the ribs, not through them.=20

It is true that a screw left in a soundboard could cause a buzz sometime =
down the road. But then so will a loose rib. Perhaps we should leave the =
ribs off as well. Seriously, enough screws have been left in enough =
soundboards over the past 150 plus years that if this were going to =
develop into a severe problem it probably would have done so by now.

Del
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