Make a soundboard--Measurements

[David Love]

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The bridge I just did I ended up laying out from scratch rather than trying to follow a pattern, an idea I got from Del Fandrich.   I found this to be easier and more accurate since I was rescaling and making slight alterations to the speaking lengths.  It also allows you to avoid duplicating mistakes on the previous layout.  The method I used was to first mark on the plate the center string locations on each hitch pin.  I used a dummy tuning pin with a string attached (Mazzaglia) which I put into the center tuning pin hole on the plate and wrapped the string around the corresponding hitch pin.   Eyeball the string in a straight line through the capo (or from the agraffe) and over the bridge and make a pencil mark right under the string on the front and back of the bridge.  Take a small straightedge and draw a line, move to the next one.  When you are done look at the overall spacing and make any corrections to get it looking even.  From there measure your speaking lengths and mark on the line the front center pin location.  Using one of several three hole punches I also got from Mazzaglia (depending on spacing), mark you pin locations.  Measure from the front row to the back row at whatever pin spacing you are using and mark the back row center pin.  Using the three hole punch, mark the back row.  At that point, if you are going to paint graphite on the bridge to, do it then, it makes it much easier to see where you are notching if your eyes aren't as sharp as they once were, like mine.  Drill your bridge pin holes.  Then mark the side of the notch at 90+ degrees (whatever you use, I use 93) off the front pin line.  I use a small piece of mylar cut at the proper angles which a lay along the pin line.  Look over your markings to see that they are evenly spaced.  Cut along the line with a small saw to uniform depth (don't overshoot the hole, use a chisel for that last bit).  Then cut your notches.  

I've gone beyond my point a bit, but I found that laying out the bridge from scratch eliminated worrying about how precise the pattern was and trying to copy it.  I still make the pattern because it gives me the location for screws in the top of the bridge when I am gluing down the new cap (on an old board), and lets me know generally where I should cut my bearing points, and out of habit.  But laying out new gave me better results and it may even have been faster.  

David Love
davidlovepianos@earthlink.net


----- Original Message ----- 
From: 
To: pianotech@ptg.org
Sent: 10/24/2003 8:37:18 AM 
Subject: Make a soundboard--Measurements


In a message dated 10/23/2003 11:19:33 AM Pacific Daylight Time, michael@gambles.fsnet.co.uk writes:
Hello RicB
It would be very important to set down the criteria for measurement of
soundboards. That must be the starting point. If everyone who wants to
partake in this research takes all the stipulated points for measurements
then there might be some realistic steps taken. Be sure to make the names of
these points international!..;-)
Regards
Michael G (UK)
----- 
     Michael, Ric Glenn
   Well, Michael, I don't know if you'd call it research. List you proposed on measuring things & observations are really probably already outlined in the journal & are just some of the measurements all soundboard installers use. 
  I.E. Measuring string heights, Plate height, bass & treble 88, mark the front corner of the plate & measure the distance fore & aft in mm to the case side. These locate the plate. Note any odd things about the bridges. I.E. inadequate side bearings, strings not going straight to the hitch pins, funky notching angels you don't wish to duplicate. Measure down to the top of the plate at the bosses. This allows you to set the height of you dowels later if you use them.
  Measure the string scale. If funky after unstringing measure string lengths & crunch the no.s. Often note 88 is too short for decent tensions in the last section. You may want to move the bridge as on many older 1800s S&S grands.
   Note the angle of the bridge top to the board. I don't often do this but every piece of info can be helpful.
   (Observation)Look at the thickness of the board thru the action cavity at the belly rail & see how it tapers. (Mental note)
  Observation) Any crown left any bearing left. Does the bearing string still touch the bridge now the strings are removed. is the bridge below the string plane?
  Pull the plate. Pull the bridge pins. make a GOOD pattern noting hole side notch cut. Use a bridge pin bit drilled straight down thru the bridge to locate the mylar pattern. Place mylar (I use 10 mil) over bridge and tap no. 6 pin thru mylar. It make a cleaner hole than drilling thru it.
  I always measure at least first and last string lengths on the long bridge & bass bridge. 
   Very important: Bridge location markers.
   I do this 2 ways. I drill straight down. straight is very important thru the top of the bridge at not 88 with a 3/16 bit and thru the board & into the belly rail. This will help locate the top of the bridge very precisely. I also do the same in the tenor end, drilling into a beam if possible. I also take direct measurements with a metric ruler to the side of the case at each end of each bridge. 
  I also measure the distance from the no. 88  bridge pin hole to the side of the case & stretcher. This eliminates the possibility of getting pattern located  wrong. There are other ways. Rebuilders please chime in.
   Drill out dowels remove treble cap screws. Now the fun part. It's time to knock the board out
   Any body tired yet? More later. going to work
  Later--Dale
  
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