The Bennett Scale - a partial archive
In the Boehm/Miller book is a picture of Boehm's own measuring tools. They all reflect a very high standard of engineering, though it is not clear which, if any, were made by Boehm himself. Possibly the sizing disks, which anyone with a simple metalworking lathe can make. I suspect the rest were commissioned by expert and specialist toolmakers, especially considering that measurements need to be accurate to at least one tenth of a millimetre.
For occasional "casual" length measurements (perhaps for checking the approximate pitch of an old flute in a shop), we need nothing more than a haberdasher's fabric tape measure. Commercial ones can be unnecessarily long. Mine came bundled with a very cheap mini sewing machine, and can measure up to 25 ins. or 640 mm.
(My most recent such use of it was to measure a B footjoint in a shop, to see if its scale and geometry was compatible with my flute. This is always an essential question to ask. The distance between the Eb and E hole centres – assuming standard modern tone hole sizes – needs to be ~30mm (for A=442) for an open-hole flute, with a latitude of ideally no more than 1mm.)
For precision scale measurements, an engineer's caliper is needed, either the classic analogue Vernier caliper, or a more modern digital one. Small ones extending to 6inches or 150mm can be found in high-street tool shops, and support precision down to 0.01mm. or 0.001 inch, and are inexpensive.
Longer calipers are available. A 300mm (12 inch) one would be enough to measure a whole instrument by summing partial measurements. The standard small caliper is such a useful tool – it can be used to measure the internal diameter of a key cup and the dimensions of an embouchure hole – that all interested flutists should have one in a drawer somewhere.
Digital calipers are available extending to as much as 100cm; a 600mm (24ins) range would be enough to cover a whole flute in a single stroke. These will represent more of an investment. Some models provide a digital connector so that readings can be directly input to a computer - the technology is much tha same as that for a Digital Readout system for a machine tool. Digital calipers of that size can be easily found via the usual internet sources.
However, the larger models use quite thick jaws, which have some disadvantages from our point of view. The smaller calipers usually have jaw tips ground down to a narrow knife-like profile, making internal tone hole and other measurements reliable, and in particular enabling measurement of the distance between the lower inner wall of the tonehole and the end of the flute, or the opposite wall of another tonehole.
For the purposes of determining the scale, we need to find and measure from the centre of a tone hole. We cannot do this directly (short of having Boehm's custom caliper); we need to use some simple arithmetic to add half the diameter of the tone hole to the length measured by the caliper, e.g. from the lower inner wall of a tone hole to the end of the foot joint.
So what of Wibb's methods? We must remember that he started on this path a long time ago, well before digital tools were widely available, or, for that matter, long Vernier calipers. Some of the papers give a few clues. In the archive folder "manyscales" is perhaps the clearest evidence for his methodology.. All these examples show use of a printed template plan of a flute, evidence if any was needed of the sometimes prolific nature of Wibb's measurement activity.
Most significantly, they show measurements made from the upper socket (which Wibb calls the "box"). The file "Arista384.jpg" (dated 1997) includes a key relative measurement "top of G to bottom of C#", with the calculation added "129.7 (253.3 - 116.65 - 6.9)".The last number is seen to be the measured diameter of the high C# tone hole. Click on the thumbnail image to see the full size document.
Compare this with the hand-drawn equivalent within the same group of files:
