I've purchased a very old piano, which is very sound musically, the the
outer shell, which is essentially a piece of furnatue) has a great
number of screws that have completely lost their threads. (The piano
lid has hinges, plus there are some other metal parts.)
I'm looking for the best way to fix this. By best, I mean most reliable
and most durable. This is the first time this problem arose for this
piano in over 100 years and I want the solution to last another 100
The opinions that I have heard are:
1. Put in a toothpick and put the screw back in.
2. Use wood putty.
3. Use plastic wood.
4. Glue the screw in with Gorilla glue
All of these sound iffy to me. So what is the best way?
>I've purchased a very old piano, which is very sound musically, the the
>outer shell, which is essentially a piece of furnatue) has a great
>number of screws that have completely lost their threads. (The piano
>lid has hinges, plus there are some other metal parts.)
>I'm looking for the best way to fix this. By best, I mean most reliable
>and most durable. This is the first time this problem arose for this
>piano in over 100 years and I want the solution to last another 100
>The opinions that I have heard are:
>1. Put in a toothpick and put the screw back in.
>2. Use wood putty.
>3. Use plastic wood.
>4. Glue the screw in with Gorilla glue
>All of these sound iffy to me. So what is the best way?
Piano restoration is a very different business than general furniture
IMHO, you need to ask these questions of someone in the piano
If you need to enlarge the hole, you do that with a drill.
The purpose of the countersink is to make a larger tapered area for the
screw to fit into. This would be what most brass has, a tapered part at the
top of the hole, so that way, the screw tops are flush with the hinge. If
you were to use a larger screw, it may stand proud of the hinge surfce.
Hence the countersink bit.
You may need to slightly enlarge the hole in the hinge as well. Use a
regular bit for than.
*Before* going larger with the screws, go *longer* with the same size.
Add about 1/2" to the existing screw length as long as you're sure the
point isn't going to come out the other side. If the screw may protrude
in a visible area, only then, go with a larger diameter screw.
I'd also try the glue and couple/three toothpicks before going to a
larger screw. Dip the toothpicks in yellow glue and insert them in the
hole - break off flush with the surface. Drive the old screw into the
hole about 1/3 to 1/2 way and leave it until the glue sets. After that,
drive the screw in the whole way and only tighten to snug down the
parts. You may have to back the screw out to break any glue bond with
the screw before driving it in completely.
in the wood and the screws don't hold tight. If
you really mean what you said (the screws lost
there treads), you just go buy new screws.
The best way is to purchase a book on furniture
and house repair and then pick 1,2,or 3 above and
As I have stated before on this forum, Toothpicks, matchsticks and wood
filler are a waste of time and effort to repair screw holes.
Drill out the old holes carefully without going clear through the wood.
Glue in a hardwood dowel with waterproof glue and trim it off flush,
then reinstall the screwsif they are in good shape, otherwise use new
I've done the dowel thing on replacing butt caps/pads on gunstocks. It
seems to me to be far the best approach. I use a small carving tool to
dress down the dowel and remove any excess glue. I've never had any
luck with the toothpick thing. I have used the wood putty approach
(fill hole, let dry, drill pilot hole) with door hinges.
That works if the screw doesn't carry any significant load. If
the screw has to support any degree of tension, the dowel will
just split lengthwise along the grain, and you'll be left with
toothpick sized splinters glued to the side of the hole.
If you have a plug cutter, cutting a long plug so that the
grain runs across the hole, instead of along it (as in a
dowel) is much stronger.
Stronger yet is filling the hole with a putty of epoxy and
sawdust (or one of the fillers made for use with epoxy).
All that said, Lew's right, musical instruments are special,
and and probably shouldn't be screwed with by the average
woodworker. At least, not if you want to preserve it's value.
I was the chief piano designer for a major American piano company for 27
years. Whenever our assembly people would strip out a screw by
overtightening it, we would require that the old pilot hole be drilled out
with a larger bit (same depth as original pilot hole) and then a hardwood
dowel (usually 3/8" dia. for screws in the #8 to #10 range) glued in place
with Franklin Titebond until completely cured (about 4 hours), trimmed flush
with a hand chisel, then a new pilot hole of the same original size (0.196"
for a #10 screw) be drilled into the center of the dowel, and then the screw
re-installed. Takes a little time, but it's the best and most long lasting
method. Occasionally we would catch them using wooden matchsticks or
toothpicks, but that's a very short term solution.
No question that your solution is the best of all
alternatives that keep the original screw. The
problem with tooth picks and matches is that the
wood is extremely soft compared to the base wood.
However, an oak or other hardwood splinter works
much better than a toothpick/match and should be
sufficient for most home repairs.
I'd strongly advise against using bigger or longer
screws for numerous reasons--splitting the wood,
changing the appearance are the two that immediately
come to mind
I'd suggest taking a block plane to a scrap of the same
wood to make come nice curly shavings. Coat them
with liquid hide glue, curl them up and and glue
those into the stripped holes with the same liquid
hide glue. Or start with veneer instead of making
your own shavings. That will fix the problem with
minimal change to the original piece.
Problems with drilling the holes larger, gluing
in dowels and then drilling those for the screws is
you'll be screwing into the endgrain of the
dowel and the dowel will be corss-grain with
respect to the part. Neither is desureable.
If the shaving method doesn't work you can
go on to try other methods. But there is no
going back from the dowel method.
Thank you for all the responses. I think that the first approach that
I'll try would be the dowel.
I that respect I have a few questions:
1. Do dowels come in all sorts of diameters - or should I drill for a
particular size? Also, if the diameter of the dowel is Xmm, should I
drill with an Xmm bit or next size down to allow for the glue?
2. Do they come in more than one type of wood? If yes, how do you
choose a best?
3. Can this be done w/o removing the hinge? Suppose I only want to
replace one screw.
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