James, I don't know about serial numbers and years for seizing Samick center pins. I haven't heard that they ever have gotten on top of this problem. I certainly would welcome the news that they have truly fixed this.
However, to diagnose the flaking center pin seizing I can tell you what I have observed:
1. Notes play better after the piano has been resting for awhile, and then start to seize worse and worse during playing. This is because the heat generated by the friction of flaking center pins makes the pins swell when the piano is played -- the harder and louder the faster they will seize up.
2, While a few notes may just be slow, because the plating has barely started to fail, mostly notes either are seized or they are not seized. Unaffected notes seem totally free most of the time.
3. More notes seize in the most used parts of the scale. That is, the plating failure is wear related.
4. Any parts can seize, but hammers tend to be the worst.
5. It seems like sometimes some batches of pins and bushing cloth are okay for some parts, but not for others -- as if certain batches are all right and others (on the same assembly line) are not. So, on some pianos, certain parts will never seize, while other parts will have lots of trouble. If you find that on a piano tons of hammers, some jacks, a few underlevers, but no wippens or rep levers are seized, the wippens and rep levers will probably continure to be fine. Or, substitute other parts -- if the jacks and underlevers are fine, but some wippen flanges are seized, expect more wippen flanges to seize later, but don't waste time repinning jacks and underlevers. On the other hand, I have had to repin every single center in a heavily used Samick grand.
6. Use a magnifying glass and a bright light to look at the seized center pin. You can usually see scoring around one or both ends, where the flakes tangled in the bushings dragged on the center pin.
7. Lubrication doesn't do the trick, though it can fool you temporarily into thinking you won't have to repin. Repin properly. I've never known a center which has been repinned with a non-plated center pin to seize up again.
8. For sluggish notes due to high humidity, using a hair dryer, hot and fast, will free up the notes. But with center pin failure, the hair dryer won't do any good.
Hope this helps ...
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Susan Kline
Philomath, Oregon
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Original Message:
Sent: 05-08-2018 23:11
From: James Kelly
Subject: samick center pin plating
I looked at a Samick model SG-185 grand serial number INIG01Z6 in a home based piano studio. the action needs some basic regulation to more life in the rep springs and get the shanks off the rebound rail however the complaint was the action was heavy to play and slow as well I did not have the tools with me because it was a visit to talk to the teachers. I tried teh tenor and bass and it seemed like lots of slow, heavy action response . perhaps it is just humidity related or the keys need a little easing but then I recalled the issues of flaking center pins on yc and samick as well as others. i can not find a list of models/serial numbers of pianos that may fall into problem center pin issues. I have had the seizure problem show up a number of times usually when tuning the piano , testing it or shortly and having to do a call back and find that new ones seized. this piano was owned by a church and i am not sure how it found its way to the studio. I recall working on a piano exactly like thi one and it was in a church. Until I check the serial numbers against one another I will not know but its possible that pianos resurface again with a new owner. so please if someone can tell me the possible year the piano was made and if it falls in the center pin plating era. i would be very thankful.
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James Kelly
Pawleys Island SC
843-325-4357
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