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Failed nickel plated center pins in Asian pianos
#3007179 07/27/20 01:55 AM
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I’ve read from a couple of places that at one point Asian pianos were using center pins with nickel plating which eventually failed and that the only remedy is to rebush and repin at the flanges. Also it was mentioned that the more use the piano saw, the more its action became unresponsive. Now that I think about about a couple of dozen pianos that I have seen, rare handful of yamaha grands with good touch were either newer or less played while majority of aging grands had stiff/sluggish action. But that might have been due to other reasons. Is the center pin problem with yamaha and other Asian pianos a fairly known thing? Have the manufactures made a switch to better center pins at some point?
Thanks!

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Re: Failed nickel plated center pins in Asian pianos
K8KT #3007300 07/27/20 11:21 AM
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This is not a problem know to affect Yamahas. It is found in Korean pianos.
It should also be stated that although this particular problem happens only with plated pins, it cannot be said that in general, plated pins react this way or that plated pins are no good. For over a century before the widespread use of materials such as "Nickel Silver", nickel-plated brass center pins were used with great success.

So, it is not that the center pins are plated, it's how you plate them.


JG
Re: Failed nickel plated center pins in Asian pianos
Supply #3007408 07/27/20 04:21 PM
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Originally Posted by Supply
This is not a problem know to affect Yamahas. It is found in Korean pianos.
It should also be stated that although this particular problem happens only with plated pins, it cannot be said that in general, plated pins react this way or that plated pins are no good. For over a century before the widespread use of materials such as "Nickel Silver", nickel-plated brass center pins were used with great success.

So, it is not that the center pins are plated, it's how you plate them.

Very informative, Jurgen. Thanks for sharing your knowledge.


Keith Akins, RPT
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Re: Failed nickel plated center pins in Asian pianos
K8KT #3007596 07/28/20 02:27 AM
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Thank you for clarifying, Supply. I understand and agree that nickel plating in general is not an issue, rather some manufacturers were installing poorly plated pins. It was briefly mentioned in Pianos Inside Out as a specific problem among the Asian pianos but I haven’t come across many sources that discuss it so I wondered how common it is/was.

Re: Failed nickel plated center pins in Asian pianos
K8KT #3007714 07/28/20 11:07 AM
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I have never seen the plating cause problems in action centers, but I have heard many people blame action centers on the pin plating. It is conceivable for the plating to get cracks when it is cut, but as far as I can tell this is misinformation based on assumptions made by people who didn't really investigate what caused problems in the bushings. In all of the actions I have repinned over the years I have yet to see any pins with plating that has gone bad or is causing issues - none.

I have investigate and repinned many, many actions where the centers became tight, and there are issues with some manufacturers at times caused by 3 common manufacturing mistakes:
- Bushings are not stable in the hole. The bushings are not inserted then stabilized through both wet sizing AND burnishing. Both steps are needed in order to leave the wool fibers in a relaxed, stable state. In these action centers the bushing cloth creeps and moves around during use, especially heavy use, and in so doing starts to bind on the center pin. This has nothing to do with the plating.
- Excess glue has soaked through the cloth and is sticking to the center pin. This can be seen when the pin is removed, as there is a ring of glue on the pin than can usually be scraped off with your fingernail.
- Burrs on the pin are snagged in the cloth, causing the cloth fibers to bind. This is caused by incorrect cutting of the pin, and has affected almost every action maker at one time or another!

All of these problems, even the glue in the cloth, can be fixed by removing the pin, burnishing the cloth to fit it to the correct pin (please don't ream the cloth with a 5-sided reamer or rat tail file!), and reassembling with that proper sized pin. It's a time consuming process, taking maybe 4 to 6 hours in total, but once the pins are fitted properly the action will be reliable as it should be. I have worked on actions of 100+ year old pianos that have had multiple sets of hammers installed on the shanks, but the bushings still are functioning perfectly! It's an amazingly reliable system.

Very high humidity does also mess with the fit of the cloth, and sometimes I have had to repin a well made action simply because it had to be fitted to work in a particular environment. Very low humidity also affects the fit, and I have repinned actions for correct friction in dry places also - not so much for reliability, but for good tone!

Solid bushing materials don't have the same humidity related issue, which is good. But humidity alone is rarely the issue for a sticky, heavy action - there are usually other factors involved that contribute.

Also, I disagree that any one country's or any one brand's actions have any of these problems - it can happen in even the finest pianos. Action center problems do tend to show up with the less experienced, lower cost piano makers - but I have seen factory screwups in literally every major brand at one time or another.


Don Mannino, MPA
Kawai America
Re: Failed nickel plated center pins in Asian pianos
K8KT #3007949 07/29/20 01:27 AM
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Young Chang did have a problem at some point with the plating on their center pins. It was flaking off, and the flakes would get lodged in the bushing cloth and cause the parts to seize up. This problem was independently observed and close-up photographs of the pins and the bushings showed this quite clearly. I am not sure what vintages were affected, I think it was in the 1990s.


JG
Re: Failed nickel plated center pins in Asian pianos
K8KT #3008318 07/30/20 03:22 AM
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Don, I really appreciate your detailed explanation on various reasons for the center action problems. Since I posted a question I’ve found more discussions online that helped me visualize each cause and the remedy for it. But 4 hours to whip up a set of bushing and pins is quite a fast pace! I do have a proper reamer/ burnisher so no making-do-with-hardware store-tools but the graduated set seems like a really good idea if one is rebushing frequently enough for different size birds eyes. I’ve realized that that was your design.

Last edited by K8KT; 07/30/20 03:22 AM.
Re: Failed nickel plated center pins in Asian pianos
Supply #3008722 07/31/20 10:29 AM
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Originally Posted by Supply
Young Chang did have a problem at some point with the plating on their center pins. It was flaking off, and the flakes would get lodged in the bushing cloth and cause the parts to seize up. This problem was independently observed and close-up photographs of the pins and the bushings showed this quite clearly. I am not sure what vintages were affected, I think it was in the 1990s.

Jurgen,
I was working for Young Chang from 1990-1995. The company had serious issues with the centers seizing up, and in 1994 I went to the factory and researched it very thoroughly with the factory staff. The problem had nothing to do with the plating - the tightening centers problem was caused by their method of installing the cloth, and the wool fibers were bunching up as I described earlier. We had an excellent stereo microscope and I did inspect the pins, no cracks or flaking of the plating.

Interestingly, before I went to Korea to work on that, I was told by multiple technicians that I should check the plating. They said that Yamaha had a bad problem with the plating cracking and flaking in the early 1980s. But I have never seen it personally - and I always figured it was just assumptions.

If you can track down who had those photos you mentioned, I'd love to see them. At one time Samick also had issues with tight centers, so maybe it was them?


Don Mannino, MPA
Kawai America
Re: Failed nickel plated center pins in Asian pianos
K8KT #3008732 07/31/20 11:46 AM
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I have never seen any evidence of plating problems when I have run into centerpin issues with Asian pianos. Most of the time I have seen signs of excess glue on the pins. A while ago someone else mentioned the plating issue and I asked if they had a picture and they posted the one I just uploaded in the gallery (sorry, I couldn't figure out how to insert it in this post). It does show the plating worn away.

I have always been skeptical of the plating idea so I was glad to see some kind of evidence. I'll leave it up to others to decide if it is proof or not.


Professional Piano Technician serving the Tampa bay area. website: mckaigpianoservice.com
Re: Failed nickel plated center pins in Asian pianos
K8KT #3008821 07/31/20 04:09 PM
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Bill, I don't know what you mean by "the gallery." If you can provide a link to that, please do.


Don Mannino, MPA
Kawai America
Re: Failed nickel plated center pins in Asian pianos
KawaiDon #3008822 07/31/20 04:15 PM
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He means the Piano Photo Gallery, lower down on this board. This is the picture:

[Linked Image]


Semipro Tech
Re: Failed nickel plated center pins in Asian pianos
K8KT #3008825 07/31/20 04:18 PM
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Don,
If you go to the opening page with all the the different forums, scroll down until you see the gallery forum.


Professional Piano Technician serving the Tampa bay area. website: mckaigpianoservice.com
Re: Failed nickel plated center pins in Asian pianos
K8KT #3008828 07/31/20 04:27 PM
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Bill, I found the picture in the photo gallery. This does not look like the plating has failed to me, it looks like a pin that has been partially worn!

When we were researching this in Korea in 1994 I could literally see scalloped grooves in the pins from individual wool fibers in the parts that were going tight in testing. When the bushings seized up the individual wool fibers literally wore away metal from the pin, and as the metal stayed in the wool fibers it accelerated the wear. This type of grooved wear was visible on both plated pins and unplated pins in the microscope we were using.

When I think of plating which has failed, I would look for cracking of the plating, peeled away areas, or other indication that the plating itself was the source of the problem. Using a microscope one would see the edges of the plating where it had come off. Discoloration all the way around the pin as this photo showed seems to be wear from the crazy tight bushing continuing to be moved.

In our testing setup we had about 6 actions mounted in machines that worked the hammer shanks up and down. We were testing different pin types, bushing cloth type, glue type, fitting procedures, sizing additives - everything we could come up with that could be a variable in the outcome. We loaded up each action with a couple of octaves of each variable, and at the end of the day turned on the machines to work the shanks all night. In the morning when we came into the room we could hear the squeaking noises from all of the shanks with tight bushings! It was amazing.

Once the fitting process was sorted out and made reliable, it didn't matter which pins were in use, none of the actions went tight. The plating which had been worn through earlier no longer did so because the bushings weren't binding on them.

The plated pins tended to be very slightly lower in friction, and the factories prefer them because they feed more reliably through the automated machinery that assembles the parts.


Don Mannino, MPA
Kawai America
Re: Failed nickel plated center pins in Asian pianos
K8KT #3008849 07/31/20 05:18 PM
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Thanks Don, you've confirmed my thoughts. It always amazed me that a piano could be used for years before problems would appear. Once they are repined though I never had anymore problems.


Professional Piano Technician serving the Tampa bay area. website: mckaigpianoservice.com

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