Alan, you are close enough. 2.5mm converts to .098" Agraffes are generally close to this too. A #40 twist drill has a diameter of .097, which will give a good visual idea of the radius. One thousanth of an inch or so is certainly a permissible tolerence Ted Sambell ----- Original Message ----- From: "Alan McCoy" <amccoy at mail.ewu.edu> To: <caut at ptg.org> Sent: Monday, April 23, 2007 12:41 PM Subject: Re: [CAUT] Hardness of termination vs string breakage (was Re: restrung D) > Ric, > > Would you mind quantifying "thin" and "sharp" for me? Ted Sambell talked > about a 2.5mm radius, which works out to 0.1" or between a sixteenth and > an > eighth inch radius (for metric-phobes). > > Thanks. > > Alan > > > -- Alan McCoy, RPT > Eastern Washington University > amccoy at mail.ewu.edu > 509-359-4627 > > >> From: RicB <ricb at pianostemmer.no> >> Reply-To: "College and University Technicians <caut at ptg.org>" >> <caut at ptg.org> >> Date: Fri, 20 Apr 2007 23:46:46 +0100 >> To: <caut at ptg.org> >> Subject: [CAUT] Hardness of termination vs string breakage (was Re: >> restrung >> D) >> >> String breakage at the capo is more complicated then just one bit. I >> have a 9 foot Petrof under my care with the same feature (actually a >> pretty good one in my book as well...) The <<soft>> capo sharpened will >> indeed groove over time... but if other issues such as speaking length >> of the string and counterbearing angle are compatible with the soft, >> sharp capo... then whatever trouble you have with string breakage must >> find its roots elsewhere. I havent seen a broken string on this Petrof >> (strangely enough) for over 18 months except in the bass and agraffe >> sections... and its played hard 6 days a week 10 months of the year. >> Three quarter medium strike weights for what thats worth. >> >> Each instrument is different to be sure, but by and large most whose >> experiences I have listened to through the years have reported fairly >> consisitently that thin, sharp, and soft works much better over time >> then wide round and soft. >> >> Again... I suggest reading McMorrow for some interesting perspectives on >> exactly this subject matter. I agree tho... the proof is in the >> pudding. I've been handling capos as mentioned in earlier posts for >> well 25 years now... and have had ample opportunity and more to watch >> the results over time. Petrofs and Bosies are not, definitely not >> proverbial high treble string breakers. God knows Petrofs have problems >> they need working out... but this is not one of them. Not in my >> experience anyways. >> >> Cheers >> RicB >> >> >> With all due respect. I had an experience several years ago with a >> Bosendorfer grand which seems to contradict this. It continually >> broke >> strings in the top section. Bosendorfer, and I believe Petrof have >> retained >> a feature found in early 19th. century pianos such as Streicher and >> Erard, >> namely, a removable treble capo bar. I removed this and found it to >> have a >> very sharp edge, and to be badly grooved, the edges of the grooves >> still as >> sharp as the unworn arears. The metal was quite soft , so I was able >> to >> easily reshape it to the radius resembling that of a 2.5mm rod, and >> polish >> it. I then re-strung the section (actually the two top sections) >> and there >> has never been a broken string since over many years. The piano is >> used >> quite heavily by good pianists. Moreover, if anything, the tone was >> better >> than before. A vibrating string is quite evidently being stretched at >> amplitude . and the consequent lengthening is offset by the >> alternating >> termination point caused by the deflection of the wire around the >> radius of >> the bar. As is said, the proof of the pudding is in the eating. >> >> Ted Sambell---- Original Message ----- >> From: "RicB" <ricb at pianostemmer.no> >> To: <caut at ptg.org> >> Sent: Thursday, April 19, 2007 3:00 AM >> Subject: [CAUT] Hardness of termination vs string breakage (was Re: >> restrung >> D) >> >> >>> >>> It is a matter of all these things, including hardness. Really, >> this kind >>> of goes without saying. A soft sharp profile will wear and >> groove, and it >>> will do so in a way that works out nicely over time. A rounded soft >>> profile on the other hand will buzz like crazy with wear. Dig out >>> McMorrows book for some good perspectives on it. >>> >>> Fred, there is friction at the bridge pin from something... this is >>> obvious because of the pins getting damaged over time. If the >> metal of the >>> pin was significantly harder then the string... these same >> moments would >>> still be at work and the wear and tear would be transfered to the >> string >>> material. >>> I mean... why would we have any use for super hard abrasives like >> diamond >>> files or any such thing unless the basic idea that harder vs softer >>> results in softer loosing ? >>> >>> Cheers >>> RicB >> -- >>
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