[CAUT] Grinding plate counter-bearing

[Overs Pianos]

Hi Don and all,

Its pretty hard, but not impossible, to get a really good job with 
the plate in the piano. Brent's suggestion of some sort of dust 
extraction system is a must, if you're doing it in the home. A useful 
tool which may work for the dust issue is a small powered dust 
collector (the type you might hook up to a 1 or 2 hp drum sander) if 
you have one. Grinding cast iron is a dirty job because the free 
carbon in the cast goes everywhere. When I have to do a job in a 
clients home which requires extraction, I use a single phase dust 
extractor (5" inlet diameter) with the collection bag removed. My 
single phase dust extractor is one of those cheap and nasty Chinese 
made things which originally had a 4" inlet diameter, and will flow 
practically nothing as a stock item. I fitted a revised inlet plate 
with a 5" diameter inlet, with a generous radius as the 5" inlet 
opens up to meet the impeller blades. The inlet and outlet safety 
mesh was also removed, since this also kills air flow. These measures 
have significantly increased the air flow. I take along enough 5" 
duct so that I can place the dust extractor outside of the house 
while running the duct to the immediate vicinity of the work. I use a 
microphone stand with masking tape to hold the end of the suction 
hose right at the dust creation source. With a few sheets spread on 
the floor it is possible to contain almost everything.

If you want to avoid damaging the plate bars, a few layers of masking 
tape on all adjacent plate surfaces will give you good protection 
against "oops" moments. Very often the surface of the plate on which 
the cast-in bars are mounted will have depressions in the cast which 
may need to be filled to provide continual support along the length 
of the new bar. I have found the tone quality will be effected if the 
bar has to span any depressions. However, car body filler is quite 
satisfactory for filling the depressions, should this be necessary in 
your particular case. You can also do spray repairs in the home 
provided that the fume extraction set up is used as described above. 
This may be necessary if depressions have been filled.

We just removed the front duplex bars and fitted continuous 
counterbearings to a Yamaha CF we rebuilt. I made a new set of 
counterbearing bars from ground stock, profiled and hardened them, 
with an EN plated surface to prevent corrosion. I'll be photographing 
this piano over the next few days, since the piano will be for sale, 
should any of you like to see some images of the finished product. We 
are asking A$120K for the circa 2000 Yamaha CFIII. It was a total 
make-over with a custom balanced set of Abel premium hammers, revised 
counterbearing bars with re-profiled capos, new agraffes, a 
rib-extended soundboard and my 1990 designed Steinway model D bass 
scale. The CF has the same bass scale speaking lengths as a model D, 
so the custom D scale fits perfectly. I am quite happy with the 
result.

Ron O.

>I have a little project I need to work on, and thought I would ask 
>for some advice.  I need to grind the treble counter-bearings off of 
>the plate of a piano in a customer's home.  I am hoping someone here 
>has a good suggestion for which tool works best to give a clean 
>removal that stays relatively flat.  I would like to avoid screwing 
>up the plate finish nearby, and leave a flat surface that I can put 
>a half-round on.
>
>With the tuning pins staying in place, I'm thinking a flat grinding 
>wheel might not fit in there.  I can use a Dremel, but am worried it 
>will be very hard to get it smooth and level.
>
>Keeping in mind the need to do it in the home, any suggestions? 
>Dremel with a specific tip, maybe?
>
>Don Mannino RPT
>


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