Cracked Plates/"Can't be welded"!

[John Delacour]

At 7:33 PM -0800 12/13/01, Joseph Garrett wrote:
>John,
>You state that plates "Can't be welded". This is very false. I personally
>have 5 pianos out there where the process was done and they span 25 years,
>for the oldest one. There is a specific process that must be done, but it is
>doable. I personally would not make any guarantees, whatsoever, and I do
>inform each client of this, but the fact is, They Can Be Welded.
>Respectfully,
>Joe Garrett, RPT, (Oregon)
>
>P.S.
>I have seen several plates that were welded "in the factory" also and are
>just fine.

Yes, perhaps I should not have made such a general statement.  I 
accept cast iron can be welded and welding "in the factory" is one 
thing.  Another thing is repairing a crack where a bar joins the web 
on a grand piano.  I'm no welder, but I understand that in order to 
remove the stresses caused by welding, the whole plate needs to be 
heated to a very high temperature.  This would completely destroy all 
the priming,filling and bronzed finish on the casting and require all 
this very time-consuming work to be done from scratch.  I've been 
through that once and I don't fancy going through it again on an old 
casting.

Besides, there are different sorts of cast iron and cast steel and I 
understand each type requires special and different treatment when it 
comes to welding.  I think I'd have to travel a long way to find a 
welder who would even be certain which metal he was dealing with, let 
alone be able to guarantee that his work would leave the material 
without severe internal stresses and that the plate would not move 
under the heating treatment.

I'd be interested to hear your and others' experience with regard to 
welding but from what I've been told in the past by good welders, I 
would be very doubtful of the long term success of welding especially 
at the critical strain-bearing points that are often in question. 
The Metallock process involves no heating at all and leaves the 
gilding intact except in the immediate area of the repair.  Apart 
from the expense of the call-out, very little extra work is required 
to make the repair invisible.  Until I hear of some fail-safe method 
of welding all piano plates, I'll stick with stitching and trust not 
to have to use either method.

JD