Measuring soundboard thickness

[Ben Bradley]

V T wrote:
> Hello List,

    Hi, VT and list, I'm new here and have been lurking for a few weeks, 
I've got piano-related questions I'll eventually ask, but thought I'd 
respond to this:

> I am sure this is old stuff for those of you who
> design soundboards, but I will post it anyway.  I
> often wondered about methods of measuring soundboard
> thickness, once the board is installed.

    While I think about it, what's the typical thickness of a piano 
soundboard? From the description in the link below, "The gauge is 
calibrated for thicknesses up to 8mm" which comes out to .315 inch.

> I was in a violin shop today and saw how violin makers
> do it.  The tool is so elegant and simple!  It
> consists of a small magnet and a spring loaded tool
> that visually resembles a long syringe.  I have no
> idea what this tool is called, so I will just call it
> "syringe".  

    I recognize this tool from the description. I saw it years ago in 
the Stewart Macdonald's Guitar Shop Supply catalog. Here it is online:

http://www.stewmac.com/shop/Tools/Calipers/Hacklinger_Thickness_Gauge.html

    I haven't seen one "in person" but it looks like quite a high price 
($385) for what it is. No doubt they charge that because (AFAIK) it's 
the only one of its kind on the market. Being an electrical engineer, 
I've thought of designing something similar that would use a Hall Effect 
sensor to measure the magnetic field strength and give continuous 
readout of thickness, and thus be both more useful and less expensive 
than this device.
    Their website shows this and two other measurement tools here:

http://www.stewmac.com/shop/Tools/Calipers.html

    Dial calipers and dial indicators as used in the "thickness caliper" 
are available from Harbor Freight:

http://www.harborfreight.com

Just type in dial at keyword, and several indicators and 6" calipers 
come up. I have one each of those as well as a 12" dial caliper from 
them I bought several years ago, though they're apparently out of stock 
on 12" ones. These are all "cheap imports" (I conveniently forget the, 
uh, Country of Origin) and are surely nowhere near the equivalent of the 
Starret brand, but with the occasional use I give them, they appear 
durable and accurate enough for me (to 1/1000th inch, I have an old 
Starrett micrometer to which I've compared measurements).

 > ...

> Vladan