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I found this yesterday while tuning.

Plate problem

Those look more like scratches from some tool used on the strings rather than fractures. There is no reason fractures would follow the line of the strings.

grey iron plates are a difficult part. They need to be cooked while cooling ( a second time) to lessen inner stresses due to the different speed of cooling between small and large portions.
Then if some stress is left the material can be brittle and react to a small stress. I have seen pianos bowed by the tension of the strings. Not sure all plates can stand a too light bracing.

look like cracks, to me, but may be only in the undercoat of the gold paint .

Again probably a Steinway I suppose

I have seen a lot of cracks in plates, but non which were straight as a ruler. It doesn't makes sense that they would be, given the structure of the material. Judging from the photos, to me it does not look like a plate problem.

Dan, I'd bet my bottom Dollar (if I had one, that is) that those are simple pencil lines on the plate finish. Methinks some kid had some fun running a pencil between the unisons. I'd take a new, soft, clean eraser to those lines and see what happens.

$0.02

While I was there I took a pencil with an eraser on the end and could not remove the marks. I was able to fit the point of a compass into the line on the left.

This is not a Steinway instrument and the manufacturer is not important. The piano is from 1996.

I am going back for a second look next week. Indeed I thought this was unusual, straight lines and all of the rest that has been mentioned.

Weird, for sure. My hunch would be that the piano will live out a normal useful life and die from worn out parts, though. Even if the cracks are structural, it is the ideal direction to have a crack. A crack perpendicular to the direction of stress would be critical.

It will be interesting to see what you come up with on further investigation. X-ray would of course be the ideal diagnostic. Lacking that, I would contemplate actually drilling a small hole in the line and seeing if there was any continuity below the surface.

It is unusual to see cracks lined up and centered within the strings like that and also so straight. In the past as a machinist I have used low viscoscity dye penatrant and developer that is made for finding tiny cracks in metal parts , so there really is no need for x-ray/ magna fluxing ect for this stuff. Sometimes castings get cooling cracks that are only on the surface and don't go too deep, but these typically show up in the areas that cooled the quickest, out near the edges and corners.

In the bottom photo, there seem to be three lines running parallel to the strings.

Before you started tuning, did you notice an unusual pattern to the out-of-tuneness? Especially near these flaws?

Did the piano hold tune well during tuning? Or, was it drifting inexplicably while you were working on it? Did the tuning seem stable after you finished tuning?

Edit: If the piano seems stable, these lines could just be artifacts from the casting process. Or, they could be the beginning of something not so good.

I assume the piano is still under warranty. You could mark these lines as well as photograph them. Then closely monitor them at each tuning for spreading, making sure to contact the manufacturer before the warranty period expires.

You could also try contacting the manufacturer directly to see if there have been any known problems with this particular piano.

I doubt the plate would tear in straight lines that appear to follow the line angle of the strings.

A couple of things to clear up. I have positioned the camera at a particular angle to show as many of the lines as possible in one shot. When looking at the piano straight on some of the lines are obstructed from view by the wire. So the camera makes it look like the lines are exactly between each unison which is not the case.

Secondly I have been tuning( or checking) this instrument every six months since 1996; that is why I am a bit surprised that I did not notice this previously. I tuned this one and then went to another room to tune another one of the same model, then came back to check something,I thought I missed on( hammer set condition) and noticed the lines then.

You know when you are tuning you look at the mutes and where they go and that is almost the exact point at which I insert them. This is why the concern, as I have never noticed this before.

No pattern of instability in the tuning noticed Joe, nothing like that at all. This has not affected the performance, stability or tuning pin torque or any other noticeable effect a twisting plate may or may not have. It is an interesting one to observe and I will continue monitor and see what develops.

I am going to take another camera with a larger lens and better macro setting to capture a couple of real close-up shots from about 4mm (1.6inches). Maybe early next week if I can get back there

Dan, it sounds like you have the situation well under control.

Another thing just occurred to me...
I wonder if the splitting is just the plate coatings and/or finish splitting. If so, this might still be a warranty issue.

Even though it may not directly interfere with the functioning of the piano as a musical instrument, this problem could affect its potential resale or trade-in value some day.

There's also the argument that this isn't supposed to happen to a plate, regardless of the actual cause.

I think the owner may likely have a legitimate warranty claim, if he cares to pursue it.

If a piano is 16 years old, does it still carry any warranty though?

Oops! My fault. Bad math. Yep, I'm embarrassed.

The chances of these being actual cracks in the casting are about 1 in zip. That is not how gray iron cracks. Ever. Given the structure of gray iron it is simply not possible; there is always going to be a slightly jagged line. Unless, of course, the frame is made of something other than gray iron and that is highly unlikely.

You may be seeing cracks in the finish or—more likely—scratch lines put there either during manufacture or—also more likely—sometime subsequently by someone who has been in there is a tool (or toy) of some sort.

ddf

(PS 4 mm = 0.1575". 4 cm (or 40 mm) = 1.575". I hate converting!)

hello. are not Yamaha frames made of another type if iron than grey iron ?

I understand the mix is different when the plate is made like aluminium parts.

we call that "aluminium iron" : even if that does not have much sence , as I dont believe aluminium and iron can mix , the process used gave the name to the material.

greetings

They are still made of gray iron. It has long been claimed that the iron used for vacuum casting. And it is quite possible that some foundries do use a slightly different mix for vacuum casting than is used for “green-sand” casting. But it’s not going to be much different. Other foundries use the same iron—it’s poured from the same kettle—for both processes. Even if the alloys vary in subtle ways they are both still classified as gray iron.

There is an alloy known a aluminum iron but it is a highly specialized material used for some pretty high-tech products and processes. I doubt it has ever shown up in cast piano frames.

Iron and aluminum powders are mixed together to make some powdered-metal products but these are usually quite small; nothing at all like the size and complexity of a piano frame.

After WW II wound down the U.S. aluminum producer, Reynolds, tried very hard to interest piano makers in casting frames out of aluminum. Several piano makers did make pianos using aluminum frames for a time but stability problems and tone problems ultimately brought this to an end and they all reverted to gray iron.

ddf

What I have read is that the metal is differnent in the end, and is sounding more strong , which is easy to verify on a Yamaha grand vs a Steinway for instance.

so more signature of the plate tone in the final mix.

I did no knew that aluminium and iron could be mixed.

Just had an article on plate design and making, but not all details in mind at the moment. But the material difference is enlighted by the factories that still use grey iron with the sand casting process.

Actually iron is not one of the 7 different alloying materials deliberately used for aluminum in its different series. The existence of brittle platelet β-Fe-rich phases lowers the mechanical properties of aluminum alloys. Iron is regarded as a contaminant of aluminum for this reason and removed/reduced by a process of intermediate phase filtration.

The pianos with aluminum plates used 5XXX or 6XXX series aluminum which uses magnesium as the primary alloy element (6XXX also includes silicon and is heat treatable). These are the same series of aluminum used in some train, truck, ship building and structural elements because they have the highest strength of the aluminum alloy groups. Purer aluminum would crumple up under the strain of a piano. I think the lowest iron content for available "aluminum iron" alloy is 20% but as Del mentioned its used in specialized application in military/space industries. I believe that aluminum iron alloy has some peculiarities in regards to eletrical resistance and thermal expansion, neither which is suitable for the pianos structural needs.

Yes, I have read that as well. Usually written by someone who doesn’t’ really know all that much about iron casting.

Yamaha grands and Steinway grands have a number of differences in both design and materials. How do you pick out exactly which differences in tone performance are attributable to variations in the metallurgy of the cast frames? As well, we should remember that the larger Yamaha frames—from roughly 200 cm and up—are all sand-cast, not vacuum cast.

The only way to really determine what tone variations can be directly attributed to one type of frame or another—i.e., sand-cast vs. vacuum cast—is to compare the identical model piano fitted with both types of frames. I’ve now been involved in two of these trials. After extensively listening to and testing several samples each of pianos fitted with each type of frame casting the conclusions were that any differences attributable to the casting methods were so subtle that they could neither be heard nor measured.

Admittedly this may not hold true for all manufacturers and all foundries but it was enough to convince me that most of what is being written about subject is both ill-informed and inaccurate and is usually done to promote one piano brand over another. In other words, it is marketing hyperbole.

I’m quite willing to be proven wrong on this but I’ll want the results of direct side-by-side testing done in such a way that it reduces any personal bias on the part of the listeners/testers to a minimum.

ddf