Frequently Asked Questions by Technicians
1. Have you ever tapped on bridge pins to get the string to take a sharper S turn, and stop the buzz? I have done this successfully many times, but am trying to find out if other tuner/technicians follow this practice.?
I assume from your description that what you are talking about is tapping or bending the pin sideways so that it exerts more pressure (sidebearing) against the string. I have seen other technicians do this, and indeed have tried it myself on occasion. From what I have observed, sometimes it works, sometimes it works for a little while and then the buzz returns, and sometimes it does not work at all. The real question is, of course, what is really causing the string buzz, and what are you really doing when you tap on or bend the bridge pin toward the string?
Based on my own experience, I tend to believe that this technique does work, but not for the reasons one might initially think. I think there are a number of things, besides increasing the sidebearing, that are happening when you tap or bend the pin sideways; some of which may help the situation for the short term, and some which may actually make things worse in the long run.
Many technicians do something called "seating the strings to the bridges" -basically tapping all the strings down to the bridge using a small hammer and a maple hammer shank or brass rod (something softer than the strings), before attempting any voicing or tone regulating. (Some technicians even do this every time they tune. (This is mostly done in grands, of course, the problem being that the hammers in a grand, over time, tend to knock the strings up off the bridge cap. In vertical pianos the hammers actually tend to drive the strings back down onto the bridge cap.) If overdone, this "seating the strings to the bridge" can leave deep grooves in the bridge top, but if done carefully, can often eliminate a number of buzzes, because it tends to push the strings back down both into contact with the bridge cap, and also tends to anchor the string back into the "V" formed by the the bridge pin on one side, and the bridge cap on the other.
Other technicians prefer to drive or seat the bridge pin further into the cap, if there is sufficient length to do so. Again, the initial or apparent rationale behind this, is that the pin is loose, and driving it in further makes it tighter. This explanation does not hold up well under closer scrutiny however, for this reason: Usually the situation is that the bridgepin is loose at the top of it's hole, because the hole has become enlarged there, generally because of the constant string side pressure on a soft spot in the wood, but also, frequently, because of sloppy pin installation technique at the factory, among other factors. If bridgepins were tapered (like some of the tuning pins of yesteryear) it might make a difference: driving the pin in further would tend to make it tighter at the top of the hole. However, driving a parallel sided pin deeper into a hole of this type will not make it tighter at the top, only at the bottom. But there is another, perhaps far more important thing that happens when you drive a bridge pin in further.
What I have noticed is that over time, strings tend to make grooves in bridge pins, just like they do in capo bars. If you have ever pulled a bridge pin out of the bridge you may have noticed a little silver furrow where the string rubbed against the pin. These grooves in the pin can cause buzzes (depending on their depth and length), and they don't have to be long. Having a bridgepin hole that is enlarged at the top aggravates this further, of course, as the bridge pin is free to vibrate independent of, and away from, the string. Also, the steel from which bridge pins are made is a harder material than the cast iron of the capo bar, and tends to be even more unforgiving of grooves, even ones that are quite short and not very deep. Usually bridge pins today are copper coated, and copper is a softer material than steel, but the copper coating is not very thick, and tends to rub through quite quickly, especially when it's a steel piano string doing the rubbing. Driving a bridgepin further into the bridge puts this groove further down and often exposes the string to fresh pin that has not been grooved, eliminating the buzz. When you tap a pin sideways, you are also putting the groove in a different position with respect to the string. But driving the pin in further may be more effective in this case, because it doesn't tend to enlarge the bridgepin hole the way tapping or bending the pin sideways does; and it also has the potential of moving the groove farther away form the string, depending on how far you drive the pin in.
However, tapping a bridgepin sideways may actually cause it to bend in the hole and make better (if not complete) contact with both sides of an enlarged hole.
Equally important to the pin is the notch and it's condition. The bridgepin and notch must work together, and the string must contact them both at the same point along its length. Notches, just like bridge pins, develop grooves and impressions, get damaged, and change their string contact point, especially when technicians get careless or too aggressive about tapping strings down to the bridge, or bending bridgepins too agressively. Bending a bridgepin sideways may actually tend to move the string sideways and out of the groove in the notch, but it also may tend to make the groove wider or worse, depending on how it's done.
Some technicians will tap the string down next to the pin (with a brass rod or screwdriver tip) so that it seats firmly between the bridgecap and the bridge pin. This often solves the buzz, at least for a time. Again, the real issue is how it's done. Too much of a tap and you put a string groove in the bridge cap, too little and you don't anchor the string .
Of course, if the buzz is caused by a rubbing damper wire, or a groove in the capo d'astro bar, or insufficient bearing against the agraffe holes (as in the topmost agraffes of some Steinway grands), or a sizzle from a duplex that is too live, no amount of bridge pin manipulation is going to fix it. It is of utmost importance to rule out these other sources of string buzzes before trying to adjust the fine contact points at the bridge. For a list of many other sources of string buzzes, please see the article in Tech Talk on "Piano Noise Troubleshooting."
Generally when we restring pianos we do something called reconditioning the bridge. We pull all the old bridge pins and swab the pinholes with epoxy. When the epoxy is dry, we redrill the holes with the appropriate size bridge drills (a few thousandths under the pin size), sand or plane the bridge cap smooth again (to clear the excess epoxy), regraphite it, renotch it and install new bridge pins. Of course, this can be done on a local basis as well.
The major concern I have about things like tapping the pin to the side to increase the side bearing is: are you actually just bending the pin, or are you enlarging the bridge pin hole at the same time, contributing to pin looseness and additional buzzing down the line? A well-designed and well-built piano should not need the side bearing (S-curve as you call it) increased. If there is insufficient side bearing to hold the string in contact with the bridge pins, I can see perhaps increasing it by the method you describe, but a better fix might be to plug and redrill the bridge pin hole in a better location, especially if sloppy drilling at the factory caused the problem in the first place. If you indeed achieve success by the former method, and the repair truly lasts, then more power to you. On the other hand, if it is only a temporary fix, and the problem returns a short time later, or returns worse than it was, then perhaps this is not the best technique to use, and some of the other methods enumerated above might work better.
One additional thing I have found causes string buzzes: Sometimes technicians over-lift the string when they are leveling the strings, or inadvertently bend the string against the top of the agraffe hole when restringing, replacing a string, or raising pitch. This can create a string bend inside the agraffe, which causes a buzz because the string then has insufficient bearing against the top of the agraffe hole. The only way to fix this is to either replace the string, or sometimes you can jockey the tuning pins (let out string on one pin and take it up on the other) so that the bend is pulled out of the agraffe.
by Kendall Ross Bean
2. How do you locate buzzes, squeaks and rattles?
See Piano Noise Troubleshooting.
3. I'm a technician in Boston, I particularly like your detailed appraisal process, and the elaborate standards you've put together. Your sample form mentions a "P. F. C. A." certification for technicians, but I couldn't find any info elsewhere about that. How can I work with you?
I am glad that you like the appraisal form. It took 23 years of evoloution for that one. Any technician can use our Piano Inspection Form for their own appraisals. Just don't represent yourself as an employee or certified by Piano Finders, unless you are.
At this current time, the only people certified by Piano Finders are those who train with Kendall Ross Bean here in California.
You can list yourself as a technician on our website if you want our clients to know about your services. There is no charge for a technician's listing.
by Karen E. Lile
