Fw: Fw: Bridge caps: box wood vs maple

[Erwinpiano]

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  Hey Rodger

 Are you currently using boxwood and do you have or know of a source?

Dale Erwin


----- Original Message -----=20
From: jolly roger=20
To: pianotech@ptg.org=20
Sent: Saturday, April 21, 2001 2:52 PM
Subject: Re: Fw: Bridge caps: box wood vs maple


Hi Ron,
             Thank's for the added imformation.

This taken from a Schimmel hand book.

Boxwood,
SG  Dependent on growing region,  0.99- 1.02
Growing regions,  large areas of Europe, Asia, Japan and NW Himalan =
regions.

Asia minor and the Caucasus is the main areas of supply.
The sapwood is pale yellow, distinguishable only by it's high moisture =
content, and is very narrow.
Depending on the growing region, the heartwood is dull to a bright =
yellow.  The pores are fine and widely seperated.=20
The wood is extremely hard.
Regards Roger




At 05:55 PM 4/21/01 +1000, you wrote:=20

  Roger, Dale and list,

  The boxwood you are referring to is Buxus sempervirens, which is a =
Roger says much harder wood than Maple Acer saccharum.

  Species         Air Dry Density (ADD)

  Maple           0.73 gr/cc

  Boxwood 0.9 gr/cc

  I prefer to rate timber density in grams per cubic centimeter, since =
water has a density of 1.0 grams/cc. This makes understanding the =
relative densities straightforward. Wood substance has a basic density =
of 1.5 gr/cc. The wood substance in the lightest hardwood Balsa ADD =
0.2gr/cc to the heaviest hardwood Yarran ADD 1.3 gr/cc is the same at =
1.5 gr/cc.

  As Ron N and Roger mentioned, Boxwood is now used for the top treble =
sections of Yamaha C series grands. Fazioli uses Boxwood for the top =
section, then Hornbeam for the next, and then maple for all of the lower =
string sections.

  Steinway Hamburg used Boxwood for the two upper treble sections until =
sometime in the 1980s. They now use maple for all Hamburg Steinway =
bridge caps. Several earlier Hamburg pianos through the 60s and 70s with =
Boxwood caps had problems. I noticed that the Boxwood they used was =
often inappropriately cut on the cross, or even slab cut in some cases.

  Boxwood is so fine its difficult to determine the grain direction by =
just physically looking at a bridge cap. But its pretty easy to see when =
an old cap is sawn through.

  I've often wondered why Boxwood bridge caps are prone to failure, but =
there are two factors on my short list of suspects.

  Firstly, with a density of 0.9 gr/cc, these caps would require a much =
larger drill than a maple cap to avoid excessive internal pressure. We =
use a drill 94% of the pin size for new maple bridges. This percentage =
would almost certainly split a boxwood cap.

  Secondly, for some years now I have suspected that the black slip =
coating which is applied to most bridges may lead to bridge damage in =
commercial usage, when subjected to high intensity lighting. The higher =
density Boxwood would be more prone to thermal damage than the lighter =
rock maple.

  Regards,

  Ron O







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