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The Crownulator
Accurately measures crown and soundboard deflection to within .001”
Measures crown easily all along the bridge even up in the high treble.
Great tool for selling the importance of new soundboards to potential rebuild clients.
Instructions for using the crownulator:
1.Measure the crown under the bridge beside each rib wherever possible.

2.Record data before and after stringing piano.

  • The rest position (fully extended, which reads o.ooo”) of the dial gauge extends from the aluminum bar by 1” (1.000”)
  • The Crownulator will therefore read a flat surface as 1.000”
  • Any deflection will be the difference of 1.000” and the gage reading. A reading of .966” for example represents a deflection of .034” (1.000-.9.66=.034)

3.The radius in feet can be determined from the following formula:

R= {(H²+1/4C²)/2H}/12

Where: H = arc deflection and C = span of Crownulator

Where the span of the Crownulator = 12”, 1/4C = 36

Thus, a reading of .034 represents a radius in feet of:


= 44.1191’


Each span is slightly different as a result of milling the stock square at the edges. You should therefore measure the span of your Crownulator and recalculate for the constant (1/4C²). You can then make a chart of readily available values or email with your exact span length and we will provide you with a chart.

Rebuilder Supplies & Services | Crownulator

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