Piano Repair: Fixing a Broken Hammer

I am not a piano repairman.  But when our piano tuner told us that it would be pretty expensive to fix our 1950s-era spinet piano (for which we paid $60), my wife urged me to try it myself.

A couple weeks earlier, one of the younger kids had been pounding on the keys, and the dowel rod holding one of the hammers snapped right off.  My wife found the broken piece inside the piano.  It was the B-flat above middle C–so not exactly a note that we could do without.

Piano Hammer Repair 2017

It’s easy to forget that a piano is both a stringed instrument and a percussion instrument.  Press a key, and a small hammer strikes a string held in tension over a soundboard.  There are 88 of these hammers, most of which strike three strings at once.  The dowel rod that held this hammer somehow snapped in two–perhaps there was a flaw in the wood, or perhaps the key was just struck too hard.  That happens sometimes when you have little kids.

Regardless, fixing this hammer was going to be tricky.  Open up the bottom of the piano, and this is what you see:

Piano Hammer Repair 2017

All those vertical, wooden pieces are part of the action–the mechanism that connects each key to each hammer.  The broken piece was deep inside this very complicated mechanism.  (Pardon the funny lighting, but the ambient lighting in my living room is abysmal, and I was working mostly by LED flashlight.)

Looking in from the top, this is what I see:

Piano Hammer Repair 2017

Somewhere down there is the other end of a broken dowel rod.  My first thought was that, if I could get the stubby end out, I could surgically insert a new dowel without having to disassemble anything.  Some older pianos, I knew, were assembled with hide glue, which will release when moistened.  I tried it out on the free end of the broken hammer, but no luck.  It’s PVA, i.e. yellow wood glue.  The whole thing was going to have to come out.

All the way out.

I had heard from pianists that it was possible to remove the entire action assembly from a piano.  I looked over the inside of the piano for quite some time, trying to see how the  action assembly was attached.  Fortunately, the internet had a helpful tutorial by a professional piano repairman.  I’m not sure I would have gotten any further without his help.

Piano Hammer Repair 2017

Once I located the points of attachment, I started carefully removing nuts and screws.

At one point, I ran across an odd little nut that looked like this:

Piano Hammer Repair 2017

I recognized it as a “split nut,” which is used on many old handsaws.  Getting one loose can be quite a trick, unless you have the right tool.

Piano Hammer Repair 2017

Which I did.

It’s an old spade bit ground down to a screwdriver shape and a notch filed into it.  I made this split-nut driver several years ago when I started working with old handsaws.

Piano Hammer Repair 2017

When I made it, I didn’t think I’d get to use it on a piano.

In order to remove the action assembly on a spinet piano, it is also necessary to remove ALL the keys.  And piano keys are NOT interchangeable.  The keys on our piano are numbered, but I still kept them all in order so as to make it easier to put them back in later.

Once the keys were all out, I was able to remove the last few bolts and screws holding the action in place.  I carefully lifted the whole thing out.

Piano Hammer Repair 2017

 

Here is the now-an empty piano with the keys lined up on the floor and the action assembly at the very bottom of the picture.  (Side note: you can probably imagine how much dust accumulates underneath the keys over sixty years.  It took us quite some time to vacuum it all out.)  The keys fit over those metal pins and rest on felt pads.  It really is an ingenious design, very complicated in some places and dirt-simple in others.

It was time to carry the whole action assembly out to the workbench.

Piano Hammer Repair 2017

If the soundboard and strings are the soul of the piano, this is its heart.  I sort of feel like I’m doing open-heart surgery here. One false move, and the patient may not survive.

Piano Hammer Repair 2017

With the action on the workbench, I carefully un-hooked and un-screwed the very-complicated mechanism that had the broken piece.

Each key is connected to a mechanism like this.  From this perspective, it looks a little like a Rube Goldberg machine.  Press the key, and a whole sequence of levers, straps, and pads moves to strike the strings.

Take a moment to appreciate how many individual pieces there are in even a small piano.  I count 14 wooden pieces all together here.  Some of the higher notes have fewer parts, but there are 88 keys total.  There over 1,000 little wooden pieces in the whole action assembly!

You can see here where the dowel supporting the hammer broke–right at the base where it was glued in.

Replacing the broken dowel was, I think, the easy part.  Once it got down to cutting and shaping wood, I felt that I actually knew what I was doing.   But order of operations was critical.

Piano Hammer Repair 2017

I first sawed the broken dowel off flush at the base.  Then I carefully re-drilled the hole.  The replacement dowel I’m using is a hair thinner than the original, but it’s dead-straight hardwood and should hold up to household use.

It took me three stops before I found a suitably tough hardwood dowel at a local hardware store.  The original one was, I think, maple or birch.  I’m not sure what species the replacement is, but it’s not poplar, which was too soft for this application.

Dealing with the other end was more tricky.  After close inspection, I noticed that the dowel went into the hammer’s head at an angle.  I would need to drill out the old dowel at the same precise angle.  So before cutting off the old dowel, I made this little jig:

Piano Hammer Repair 2017

In a squared-up piece of scrap, I cut a small dado to fit the hammer and wedged it in upside down.  I then inserted a long, pan-head screw into one end of the underside so I could raise the whole jig up at an angle by turning the screw. I sighted the dowel along an upright square and, by trial-and-error, found the precise angle at which the dowel was inserted.

I sawed off the old dowel and took my jig and workpiece down to the drill press.

Piano Hammer Repair 2017

It was easy to drill the hole at the correct angle.

I glued in the new dowel and went and had a cup of coffee while the glue dried.  (Sorry, no picture of the fixed mechanism.  I was so tired that I forgot to take one!)

It wasn’t easy getting the repaired mechanism back into the piano.  Having one or even two people to help guide it in was very helpful.  The more you bump things inside a piano, the more out of tune it will be.  And I sure didn’t want to break any more pieces on this action assembly!

My oldest daughter kindly helped me put the keys back on, too.

Piano Hammer Repair 2017

Keys, nuts, screws–all had to be reinserted exactly as they had come out.  It was especially annoying to reattach the damper and sustain pedals.

Piano Hammer Repair 2017

Finally everything was back in place.  It was a lot of work to fix a little piece.  It kind of reminded me of car repair–and not necessarily in a good way.  I had to remove so many components in order to replace one little piece without which the whole thing wouldn’t work.  At least it leaves my hands less greasy.

Now, of course, the piano needs to be tuned again.  But it plays.  And I fixed it all by myself.

 

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2 Responses to Piano Repair: Fixing a Broken Hammer

  1. floschulerhotmailcom says:

    Wow what a job! I guess it is understandable why this repair would have cost a lot money. Thank the Lord you started working with wood ten years ago and that instructions on almost anything can be found on You Tube. I am proud of you, son.

  2. Coisas EM'adeira says:

    Such a great story!
    Congratulations!!!!

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