An added complication is that piano wire often thins after being repeatedly stretched, or under tension. I frequently find even on U.S.- made pianos that when I am mic'ing the wires to measure the sizes for restringing, that the wire is frequently under by .005" or even .001" from the wire sizes marked or from what I expect to see. It seems sometimes as if this may be less pronounced on newer pianos that haven't been tuned or played much, and more pronounced on older ones that have been tuned many times and played hard, or that have never been restrung for many many years. (In addition, I don't think the wire they often used to string pianos at the factory (or subsequently) was always exact or of the highest tolerance to begin with.) German wire seems to be more consistent, but even there, there are exceptions. I think all these factors need to be taken into consideration. Another complication is that the factory or previous stringer may have lost track of string sizes, or missed a size change. This is most apparent when you encounter a size change within a unison, or when one size seems to go on far longer than it should (except apparently for size 17 wire!). It's often difficult pinpointing the exact reason for unexpected wire sizes. But yes, the German wire diameters do run somewhat smaller than the U.S. wire sizes, for any given wire number. For example, my Renner catalog lists #14 German (Roslau) wire as .825 millimeter, which corresponds to .032480" or roughly 32.5 thousandths on the micrometer, which is in-between a U.S. size 14 and a 13 1/2. Thinning of the wire, or poor wire tolerances, might make the wire look even smaller: -more like a size 13.5 U.S. (or even a size 13 in some cases). The difference becomes more pronounced at larger wire sizes. A number 20 Roslau wire is listed as 1.125 mm or .044291" (roughly 44.3 thousandths on the micrometer). For comparison, a U.S. size 20 wire is supposed to be 45 thousandths of an inch (.045"). Somewhere someone had posted a chart of the differences in German and U.S. wire sizes. If I remember where I saw it, I will post it, or a link to it. But if you have a Renner catalog you can look up the measurements of German wire. I think it was Ron Nossaman who hinted once that he felt the U.S. piano supply companies might be "translating" the sizes of German and Japanese metric tuning pins and wire to U.S. sizes, because of this very issue. But I think you are right David, to use the size 17.5 instead of the size 18 (unless the wire has really thinned under tension.) When restringing Japanese or German pianos, you really have to rely on the micrometer instead of the marked numbers. (P.S. One added headache is that there doesn't seem to be any uniform system for marking the wire numbers on the plate or the bridge. Some piano makers stamp the numbers so as to indicate a size change to the left, others to indicate a size change to the right, apparently depending on which direction the piano was being strung. And not all pianos start with size 13 wire in the high treble, or size 20 at the bottom of the plain wire sections.) Kendall Ross Bean PianoFinders -----Original Message----- From: David Ilvedson [mailto:ilvey at sbcglobal.net] Sent: Thursday, January 29, 2009 10:28 AM To: caut at ptg.org Subject: Re: [CAUT] Wire gauge question Metric...European pianos are the same...I posted an email, to no response, about changing a string in the tenor on a Hamburg D. Hamburgs use Roseau piano wire, so I bought 17.5 and 18 sizes from Schaff. The string in question shared 2 unisons. Piano said 18. My micrometer said 17.5 My Schaff Roseau wire said 18 and was 18(American). I used the American labeled Schaff 17.5 Roseau wire where the piano said 18, of course. Why wouldn't the Roseau wire be labeled as 18 metric? You have to always mic the wire... David Ilvedson, RPT Pacifica, CA 94044 ----- Original message ---------------------------------------- From: "Zeno Wood" <zeno.wood at gmail.com> To: "College and University Technicians" <caut at ptg.org> Received: 1/29/2009 7:14:02 AM Subject: [CAUT] Wire gauge question >Ok, what's going on here? Would a Yamaha CFIII be using a different >system of wire gauge? It says 14 or 14.5 on the bridge, but it >measures more like .032" which is 13.5 - is this metric? If so, whose >idea was it to make metric and "normal" so close to each other? >Thanks, >scratchin' my head...
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