Pianotech

Hi Tom,

For Yamaha pianos, it's worth setting aside the American Wire Gauge designations altogether, for two reasons. First of all, the wire they were manufactured with conforms to a metric sizing specification, and second, I understand most of not all piano wire currently available for purchase in AWG sizes to actually be wire manufactured in metric sizes, then relabeled with AWG for use in the USA.  When I purchase wire, I label the spools with both the AWG and metric gauges, and also the diameters in both inches and millimeters.

Stephen Paulello has a handy chart that I have printed out and refer to often.  Its gauge numbers are the metric ones.  

https://spaulello.com/wp-content/uploads/2025/03/Inches-mm-conversion-table.pdf

The C3 handiest to me is from 1977, and has notes 27 and 28 at 18 1/2,  then the next ten notes at 18, as indicated by the ink stamps on the bridge.  Again these are the metric gauge numbers.

I would understand the markings on your bridge to indicated the intent of the manufacturer.  Sometimes work that does not match spec escapes from the factory.  Sometimes we run into a previous restringing job where different decisions were made.

If you have a strong enough desire to investigate further, I recommend becoming familiar with Tremaine Parson's PScale program.  Stephen Paulello's hybrid stringing approach adds yet another fascinating layer.

I trust this is helpful.

Hi Tom,

For Yamaha pianos, it's worth setting aside the American Wire Gauge designations altogether, for two reasons. First of all, the wire they were manufactured with conforms to a metric sizing specification, and second, I understand most of not all piano wire currently available for purchase in AWG sizes to actually be wire manufactured in metric sizes, then relabeled with AWG for use in the USA.  When I purchase wire, I label the spools with both the AWG and metric gauges, and also the diameters in both inches and millimeters.

Stephen Paulello has a handy chart that I have printed out and refer to often.  Its gauge numbers are the metric ones.  

https://spaulello.com/wp-content/uploads/2025/03/Inches-mm-conversion-table.pdf

The C3 handiest to me is from 1977, and has notes 27 and 28 at 18 1/2,  then the next ten notes at 18, as indicated by the ink stamps on the bridge.  Again these are the metric gauge numbers.

I would understand the markings on your bridge to indicated the intent of the manufacturer.  Sometimes work that does not match spec escapes from the factory.  Sometimes we run into a previous restringing job where different decisions were made.

If you have a strong enough desire to investigate further, I recommend becoming familiar with Tremaine Parson's PScale program.  Stephen Paulello's hybrid stringing approach adds yet another fascinating layer.

I trust this is helpful.

I'm inclined to think it was a "boo boo". 

Peter Grey Piano Doctor 

Hi Tom,

For Yamaha pianos, it's worth setting aside the American Wire Gauge designations altogether, for two reasons. First of all, the wire they were manufactured with conforms to a metric sizing specification, and second, I understand most of not all piano wire currently available for purchase in AWG sizes to actually be wire manufactured in metric sizes, then relabeled with AWG for use in the USA.  When I purchase wire, I label the spools with both the AWG and metric gauges, and also the diameters in both inches and millimeters.

Stephen Paulello has a handy chart that I have printed out and refer to often.  Its gauge numbers are the metric ones.  

https://spaulello.com/wp-content/uploads/2025/03/Inches-mm-conversion-table.pdf

The C3 handiest to me is from 1977, and has notes 27 and 28 at 18 1/2,  then the next ten notes at 18, as indicated by the ink stamps on the bridge.  Again these are the metric gauge numbers.

I would understand the markings on your bridge to indicated the intent of the manufacturer.  Sometimes work that does not match spec escapes from the factory.  Sometimes we run into a previous restringing job where different decisions were made.

If you have a strong enough desire to investigate further, I recommend becoming familiar with Tremaine Parson's PScale program.  Stephen Paulello's hybrid stringing approach adds yet another fascinating layer.

I trust this is helpful.

I think I would be inclined to follow what is stamped on the bridge. The below data came from North Bennet Street School and was represented as original but I am not sure that the plain wire sizes have not been tweaked. The DIAM numbers are in thousands but the actual calculations are based on the smaller metric diameters. So 13.5 = .032 is calculated using .0315 as a diameter. Metric wire of the same gauge as American are .0005 smaller gauges 12 through 14.5 , .0006 smaller gauges 15 through 18 ,  .0007 smaller gauges 18.5 through 21 , .0008 smaller gauges 21.5 through 22.5
Gauges 23 and up are nearly the same (23 = +.0002, 23.5 and up +- .0001) Graph included below data.

Piano Mfg/Info/Filename: yamc3o.txt / YAMC3NBO |
Default Unified Gauge Method.
Use Metric Core Wire is checked. TEN, Brk%, and INH are correct. Calculated with actual smaller metric plain/core wire conversion sizes.

I'm inclined to think it was a "boo boo". 

Peter Grey Piano Doctor 

Hi Tom,

For Yamaha pianos, it's worth setting aside the American Wire Gauge designations altogether, for two reasons. First of all, the wire they were manufactured with conforms to a metric sizing specification, and second, I understand most of not all piano wire currently available for purchase in AWG sizes to actually be wire manufactured in metric sizes, then relabeled with AWG for use in the USA.  When I purchase wire, I label the spools with both the AWG and metric gauges, and also the diameters in both inches and millimeters.

Stephen Paulello has a handy chart that I have printed out and refer to often.  Its gauge numbers are the metric ones.  

https://spaulello.com/wp-content/uploads/2025/03/Inches-mm-conversion-table.pdf

The C3 handiest to me is from 1977, and has notes 27 and 28 at 18 1/2,  then the next ten notes at 18, as indicated by the ink stamps on the bridge.  Again these are the metric gauge numbers.

I would understand the markings on your bridge to indicated the intent of the manufacturer.  Sometimes work that does not match spec escapes from the factory.  Sometimes we run into a previous restringing job where different decisions were made.

If you have a strong enough desire to investigate further, I recommend becoming familiar with Tremaine Parson's PScale program.  Stephen Paulello's hybrid stringing approach adds yet another fascinating layer.

I trust this is helpful.

Actually, I'm not 100% sure the above data is from a Yamaha C3 but that is what the file name indicates. Speaking lengths in mm would need to be compared.

I think I would be inclined to follow what is stamped on the bridge. The below data came from North Bennet Street School and was represented as original but I am not sure that the plain wire sizes have not been tweaked. The DIAM numbers are in thousands but the actual calculations are based on the smaller metric diameters. So 13.5 = .032 is calculated using .0315 as a diameter. Metric wire of the same gauge as American are .0005 smaller gauges 12 through 14.5 , .0006 smaller gauges 15 through 18 ,  .0007 smaller gauges 18.5 through 21 , .0008 smaller gauges 21.5 through 22.5
Gauges 23 and up are nearly the same (23 = +.0002, 23.5 and up +- .0001) Graph included below data.

Piano Mfg/Info/Filename: yamc3o.txt / YAMC3NBO |
Default Unified Gauge Method.
Use Metric Core Wire is checked. TEN, Brk%, and INH are correct. Calculated with actual smaller metric plain/core wire conversion sizes.

I'm inclined to think it was a "boo boo". 

Peter Grey Piano Doctor 

Hi Tom,

For Yamaha pianos, it's worth setting aside the American Wire Gauge designations altogether, for two reasons. First of all, the wire they were manufactured with conforms to a metric sizing specification, and second, I understand most of not all piano wire currently available for purchase in AWG sizes to actually be wire manufactured in metric sizes, then relabeled with AWG for use in the USA.  When I purchase wire, I label the spools with both the AWG and metric gauges, and also the diameters in both inches and millimeters.

Stephen Paulello has a handy chart that I have printed out and refer to often.  Its gauge numbers are the metric ones.  

https://spaulello.com/wp-content/uploads/2025/03/Inches-mm-conversion-table.pdf

The C3 handiest to me is from 1977, and has notes 27 and 28 at 18 1/2,  then the next ten notes at 18, as indicated by the ink stamps on the bridge.  Again these are the metric gauge numbers.

I would understand the markings on your bridge to indicated the intent of the manufacturer.  Sometimes work that does not match spec escapes from the factory.  Sometimes we run into a previous restringing job where different decisions were made.

If you have a strong enough desire to investigate further, I recommend becoming familiar with Tremaine Parson's PScale program.  Stephen Paulello's hybrid stringing approach adds yet another fascinating layer.

I trust this is helpful.

I thought I replied to this and now I can't fid it...pardon the potential duplicate. 

From memory C#4 (key #41) is 17, which I know from a C3X warranty issue with a distinct and loud high tension sizzle. One of the tricks we use to test this theory is to change the wire size. I put a 16.5 on and that didn't do it. Yamaha asked me to return and install  17.5. 

This has to do with longitudinal waves. 

So it may have left the factory like that, or may have been corrected as some point. 

Just a guess based on recent experience. 

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Vincent Chambers

Apollo Piano | Stanford University
San Francisco, Chico CA
(530) 924-4469 Mobile; 732-642-1100
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