John: If you find excessive flex in the key, how do you address it. David Love davidlovepianos@earthlink.net > [Original Message] [link redacted at request of site owner - Jul 25, 2015] > To: Pianotech <pianotech@ptg.org> > Date: 5/1/2003 2:26:34 PM > Subject: Re: Key Leads and Inertia > > Ron Nossaman wrote: > > > Del, > > You knew this was coming, so I won't make you wait any longer. Do you > > have any rough rule of thumb go - no go diagnostic criteria for deciding > > when keys are too flexible during teardown? > > > > Ron N > > > Ron, I hope you don't mind if I weigh in on this. I use a 1000g weight > applied to the end of the key (naturals). If the weight bends the key - > measured with a dial indicator - more than 1mm I consider it to be a > problem, ideally is should be under 0.75mm. The key is removed from the > key frame and placed on a work bench. The key is supported under the > balance rail hole and under the capstan. A clamp is place to hold the > key down near the capstan. The weight dangles from a cord off the > playing end with an indicator close by it. The weight is slowly lowered > and a reading is taken. Average several reading to find the key flex. > > I derived the 1mm using data in Pfeiffer's book "The Piano Hammer". > Using the force applied to the key during load play I came up with a > figure that would bend the key 10mm. This along with personal experience > led to my rule - no more flex than 1mm at 1000g. > > John Hartman RPT > > John Hartman Pianos [link redacted at request of site owner - Jul 25, 2015] > Rebuilding Steinway and Mason & Hamlin > Grand Pianos Since 1979 > > Piano Technicians Journal > Journal Illustrator/Contributing Editor [link redacted at request of site owner - Jul 25, 2015] > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives
This PTG archive page provided courtesy of Moy Piano Service, LLC