Pinblock plugs are a viable long-term repair. You can get them in
either 3/8" or 1/2" diameter.
Don't drill all the holes out at once. Alternate them. Some holes
you may want to place the smaller plug where the pins are really close.
Cover the plugs with a cloth as you drive them in to avoid splatter.
Use a high grade epoxy, not the 5-minute variety. West Systems is
a good line: their fillers and fairing compound allow you to mix an
adhesive to any desired consistency. However, I prefer to use these
additives with epoxy from Epoxy Technology, Billerica, Mass., tel.
978-667-3805, fax 781-272-1530
Their 301 is a water thin (really) material which is approved by NASA
for space flight programs. It is use mostly for fiber optics but has
many other uses. A 1-pound can is $36.75 ppd. (as of 2/99).
It is great for sound board cracks. I wet the surfaces first with
it thin, then mix in filler, and wood flour or fairing compound for
coloring. I tape the surface of the board and invert the piano to
inject the epoxy from the back/bottom. Otherwise you would tape
between ribs and alongside the crack on the surface.
One problem with cracks is that the wood cells have suffered compres-
sion damage or dry rot. Wood glue does not soak in like the water thin
epoxy does.
Last summer I repaired an old Bechstein grand where 15 years ago a
'tech' had plugged the block. Unfortunately he did not attend to the
cracks in the block itself and the tension eventually cracked the block
further, aside from a sloppy job; the plugs were not holding. Wrong
glue.
The block was mortised into the case. The case and veneer were fragile
so I opted to make an inlay of pin block stock. I drew out an outline
and made a pattern to rough cut the inlay. A bench top drill press and
a Forstner bit removed the old pinblock material down to the bottom few
laminations leaving the sides to be cleaned up with a chisel. The
inlay was dry fit nice and snug.
Being an exposed block I applied the face veneer and finished. Then
mapped the holes, removed the inlay and drilled the pin holes on a
drill press. 301 was applied to wet the surfaces and then filler
added. The next day, after it set up, I poured more epoxy into the
margins where it pulled in. The plate flange to block mating was
reinforced with Marine-Tex.
I was quite pleased with the results. This piano also necessitated
me to design a new tool for gluing the sound board back to the ribs
without the use of screws. I have use them for gluing bridge caps
as well. I have an image file if any one wishes to view the pressure
applicators.
I need to get a coffee...
Jon Page, piano technician
Harwich Port, Cape Cod, Mass.
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