[pianotech] Yamaha C7 scale

Nick Gravagne gravagnegang at att.net
Sat Mar 7 13:43:50 PST 2009



Attached find a Word File chart that compares Standard piano wire gage
values to Metric. I used standard metric-to-inches conversions.

I put this together rather quickly, so please study and let us all know if
there is a problem with it, if I misssed something. I think it looks
correct, though.

A bit of perspective (for example note# 21):

1800mm long, standard gage 21 (0.047"): Ten = 195; BRK% = 35; INH = .059

Same note using metric gage 21 (0.0463"): Ten = 189; BRK% = 35; INH = .057

Not a big difference, and over the span of an entire scale a change from
standard to metric might reduce the overall tension by, say, 1100 to 1500
pounds of pull (a quick calculated guesstimate). Still, should be kept in
mind. 

Changes in whole sizes with either gage protocol, however, are more
significant;

1800mm long, standard gage 20 (0.045"): Ten down to 179 (From 195); BRK% =
35; INH = 0.054

1800mm long, metric gage 20 (0.0443"): Ten down to 173 (from 189); BRK% =
35; INH = 0.053

Regards,

Nick Gravagne, RPT
Piano Technicians Guild
Member Society Manufacturing Engineers
Voice Mail 928-476-4143
 
 

>   Don't forget these are metric wire sizes. The size listed will be a 
> 1/2 size larger or smaller than standard sizes. I forget right off the 
> cuff. I think adding a 1/2 size to the stated number makes them the 
> correct diameter.
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