Keytop Replacement

A few posts ago, I wrote about a Milton player piano that I had acquired.  The keys were not in the best shape; the front and balance rail bushings were falling out, the key buttons were coming unglued, and most of the keytops had come off or were just barely hanging on.

I ordered a full set of Gloss White Vagias Plastic Keytops with short heads from Schaff Piano Supply, as well as a set of 3 1/2" Gloss Plastic Sharp Keytops for the black keys. It is important to get the right length of keytop to minimize the amount of sanding and filing of the keytops later on.

You can see the original ivory keytops above.  They look terrible and need to be removed.  The black ebony keytops have already fallen off.  To remove the remaining ivories, loosen the glue by covering them with a damp cloth and steaming them with a hot clothing iron.  Keep the iron moving and steam each area for 5 seconds or so. 

When the glue is adequately  loosened, the keytops should pry off the keys with very little effort.  If the glue is still holding, re-steam the keys to reduce the risk of prying any wood chunks off with the keytops.  For the black keys, repeat the same process, except steam the sides of the keytops instead of the top.

After all of the old keytops have been removed, the keytops need to be prepped for the new keytops.  This means making the top surface of the keys flat, as well as reducing the thickness of the keys if the new keytops are thicker than the old.

I use a table saw to accomplish both of these tasks at once.  Because the old ivories are significantly thinner than the new plastic keytops, I set the fence to remove about a millimeter from the tops of the white keys.  I clamped a block to the back of the fence to act as a depth stop, as well as a block to the table to mark the fence adjustment, which allows me to move the fence away after the key has been trimmed, and precisely move the fence back after the key has been pulled away from the blade.

Raw key after removing the keytop

Key after facing on the table saw

After trimming all of the white keys, I make sure all of the keys are flat by gluing some sandpaper to a precision ground surface (I use a slab of marble countertop) and sanding down any irregularities.

The keys are now all prepped and ready for the new keytops.  I use contact cement to attach the keytops.  Contact cement works by brushing some cement onto both surfaces, and then waiting some time for it to partially cure before clamping the two surfaces together.

The front ends of the white keytops are rounded and are meant to overhang the end of the keys by a few millimeters.  In order to get a consistent amount of overhang, I use a simple jig made of a couple coins and a bit of cardboard.  One of these days I will make a nicer jig out of wood, but this works for now.

Cement applied to key and keytop

Place the white keytop on the key with the end butted up against the gauge.  Press down firmly and then clamp the key firmly in a woodworking vise to set the ketyop.  Repeat this process with the black keys, but just align them visually, no need for any kind of jig.

After the cement has dried the keytop may need a bit of sanding or filing to make the edges flush with the key body.  Do this carefully, as it is easy to quickly ruin the appearance of your new keytops.

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Hammer Spring Replacement ("Sticky Key")

A neighbor was getting rid of this wonderful little Kohler Campbell console piano a few weeks ago.  Overall, it was in really good shape and just too good of a deal to pass up.  We picked it up, brought it home, and I proceeded to tinker with it for a little while to find any problems.

The only information that the former owner was able to give me was that there were some "sticky keys".  This means that a key will produce a sound the first time it is struck, but will not sound with any following strikes.  This is probably the single most common issue that people come across in their pianos, not only because people lump several different symptoms under the label "sticky key", but also because there are probably over a dozen different issues that can cause a sticky key.  

It turned out that the only major problem with this piano was that nearly all of the hammer return springs had corroded and broken.  These springs only exist in upright pianos (their role is fulfilled by gravity in grand pianos).  Their function is to assist the hammer in falling back to its rest position after striking the string.  If they are broken or disengaged, the hammers will not consistently return after striking.  This will cause missed strikes during which a key will be pressed, but no sound will be produced.  

Hammer return spring circled

Above is the piano action as it should look, with all hammer return springs intact.  This photo was taken after I had finished repairing the springs.   Below to the right, you can see how the spring rail looked originally with all of the broken springs still on it.  Below to the left, you can see the piano action with the spring rail and hammer rest rail removed.

Piano action with hammer return spring rail and hammer rest rail removed

Hammer spring rail

For this repair, I needed to remove the spring rail from the rest of the piano action, but in order to access the screws that hold it on, I first needed to remove the hammer rest rail.  This rail is held in place by four steel pins with 90 degree bends in them.  Three of the bends point one direction and one points the other direction.  Once the oddball pin is removed from the action, the remaining three pins will all slide out in the same direction and the hammer rest rail can be removed.

Apparently in some pianos the oddball pin is spring-loaded or has some other method of easy removal.  This piano, however, has no such device, and so the action bracket that the pin is inserted into must be pulled away from the pin. There are two screws on the lower end of the action bracket that, if removed, allow the bracket to be pivoted enough for the hammer rest rail pin to be removed.

Hammer rest rail showing the four pins that hold it in place

Opposite facing pins

After removing the hammer rest rail, the four screws that hold the spring rail in place can be removed, and the rail can be slid sideways out of the action.

First, I need to remove all of the old springs from the rail.  There is a hole through the rail that the tail of each spring is fed through.  The tail is then bent sharply downward by a machine (which leaves the two parallel indentations) into a slot which holds the end of the spring tightly.  I don't own one of these machines, so when I install new springs, I will be making a modification to this rail so that I can install them tight enough.

First, I remove the strip of felt that is covering the ends of the spring tails.  The glue holding the felt down can be loosened by applying some diluted wallpaper remover to the felt and allowing it to sit for a half hour or so.  After removing the felt,  pry the tails of the springs out of their slots by using a sewing needle and a small screwdriver.  Then, grasp the coil of a spring with a small needlenose pliers and use the pliers as a lever to pull the spring out of the rail.

An intact spring, one with a broken end, and one with a broken tail

Hammer spring carnage

New spinet springs

There are several different lengths of these springs, so make sure you buy the correct length for your piano.  My piano is a console, so I bought the "spinet" length springs.  The measurement you need is from the coil to the end of the curvy part.

The modification that I mentioned earlier involves drilling an extra hole for each spring through the spring rail.  Some piano manufacturers make spring rails that already have two holes per spring like this.  The advantage is that the second hole will allow me to pull the tails really tightly into the wood with a pair of pliers, and eliminates the need for the specialized "parallel indents" machine.

To make the holes, I clamped a drill bit just slightly thicker than my spring tails into a pin vise.  I then inserted the pin vise into my drill press.  The reason for the pin vise is that the chuck on my drill press can't clamp onto something as small as this drill bit.  The slots in the rail give me a nice little guide for the drill bit.  I'm aiming to go through the rail right at the top of where the strip of felt was glued down.

After I've drilled all 88 holes, I can start installing my new springs.  I insert the tail through the rail, and use a wire-bending pliers to create a 180 degree bend in the tail.  The tail can then be pushed through the hole I just made until it pokes out of the same side of the rail as the body of the spring.   I then grab the tail with a set of linesman pliers and, using a lever motion, pull any slack out of the spring until the coil is nice and snug up against its felt.

The springs will tend to need a bit of manual aligning and straightening after they are all installed.  After they are all aligned, go through and snip the tails as close to the rail as possible.

The finished installation

When all of the springs are on the rail, remember to glue your strip of felt back onto the rail (which I forgot in the picture above), and carefully slide the rail back into the action without catching the springs on any other action parts.  Reinstall the screws that hold it in and reinstall the hammer rest rail.

The springs will probably need to be bent toward or away from the hammers a bit to make the action feel normal again.  I try to make them so that they are just barely putting any pressure on the hammers when at rest.  If they are applying too much pressure, the hammers will return very quickly, but the action will feel very heavy and cumbersome.  Too little pressure and hammer return will be inconsistent and the springs may "click" against the hammers when the note is played.

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Loose Tuning Pins CA Glue Repair

The Kimball upright that lives on the covered back porch at my house has had plenty of issues that I've been knocking out one at a time over the past year or two.  Probably the most annoying problem is that many of the tuning pins are not as tight in the pinblock as they should be.  The pinblock is a laminated block of hardwood mounted in the piano with holes drilled in it that the tuning pins fit tightly into.  In this piano, as with many others, the pinblock is hidden behind parts of the piano cabinet as well as the cast iron plate.  Some of the tuning pins here turn with only a pinky finger's worth of force on my tuning wrench.  That's not good, and it means that this piano only holds a tune for a very short amount of time before the tension of the strings and the pounding of the hammers causes them to go flat.

In Pianos Inside Out by Mario Igrec, he describes several labor-intensive processes to remedy this problem including replacing the original tuning pins with oversize ones or even replacing the entire pinblock.  However, he also details a much simpler process that can be used if the pinblock still has integrity but just needs a bit of extra friction on the tuning pin.

To tighten up the tuning pins, he recommends treating the pinblock with CA glue (a.k.a. "super glue").  The piano needs to be laying on its back so that gravity will pull the glue through the holes in the cast iron plate and into the pinblock.  In the picture above, I've strapped the piano to an appliance hand truck which will give me more control when tipping the piano.

Here you can see the holes in the plate that I will be feeding the glue into.  In some pianos there are wooden bushings that support the pin as it passes through the plate.  This piano does not have these bushings.  This makes applying the glue much easier, since it doesn't need to pass through a bushing before getting to the pinblock.

I ran a couple of two-by-fours down through the handtruck in order to get more leverage while tipping the piano.  These things are heavy, so make it as easy as you can and get a friend or two to help.

I've also laid down an even larger board that I will rest the piano on.  This board will make it easier to get the piano back upright after the repair is finished.  Make sure you remove the action from the piano before you tip it over!

Here is the glue that I will be using.  I bought this from the wonderful folks at Pianotek Supply Company.   Basically, this stuff is just really thin super glue.  Normal super glue is too thick to really penetrate into the pinblock.  Don't glue your fingers together and try not too breathe in the fumes.

The little straw helps me to get the glue right into the tuning pin hole.  I just keep adding glue until it seems saturated and the hole stays full for a few seconds.  All of the tuning pin holes need to be glued in one pass because after the glue has dried the pinblock will be sealed and any glue applied after that won't penetrate the wood.

Tuning pins before applying CA glue.

Tuning pins after applying CA glue.

I ended up using a little under 2 oz. of CA glue for this, which is less than half of the bottle that I bought, but would have been about 20 of the standard size tubes of super glue.  I let the pins dry a few hours before tipping the piano back upright.  I then let it dry another couple of days before attempting to tune it and I can say that there is definitely an improvement in the torque required to turn the tuning pins.  Apparently there is debate about the longevity of this repair which I can't comment on yet, but I'll revisit this post later to comment on it.

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Replacing a Broken String

Broken strings can be a common occurrence on certain pianos, especially if it is an older instrument, has been exposed to high humidity, or is played with a heavy hand.  Most of the time, the strings that break will be the thinner ones in the highest section of the piano.  Unlike other string instruments in which each string only has one speaking segment, these strings actually have two.  The string starts at a tuning pin at the top of the piano, runs down through several guides, does a 180 degree bend around a hitch pin at the bottom, and then runs back up through more guides and into another tuning pin.  Except in the bass section, each note of the piano is produced by three different speaking lengths of strings.  I have already replaced several strings in this piano (the new ones are much shinier), but still have a few to replace.

The first step is to cut the broken string just below the v-bar in order to make removal easier.  The string must be measured with a micrometer or caliper to ensure that it is replaced with a string of the same thickness.  Treble piano strings range from size 12 (.029" diameter) to size 22 (.049" diameter) and come in 1/2 size increments.  This means that there is only a .001" difference between any two sizes.  Piano wire sizes can be confusing if you are familiar with wire gauge sizes which get larger in diameter when the size number gets smaller.  Often times, the string to be replaced will measure as in between two sizes (e.g. .0335").  In this case, choose the larger size as the string will tend to get slightly thinner as it is stretched while tuning.

The left tuning pin can then be loosened (turned counterclockwise) one half a turn, and the remaining coil can be pried off with a needle-nose pliers and screwdriver.  The same can be done with the right tuning pin except with a full turn counterclockwise.  The picture above shows the two tuning pins after the old coils have been removed.

Piano wire can be purchased in short lengths for the replacement of a single string or in various sorts of coils like the one shown above.  Long lengths of wire are very springy and can quickly get out of hand if not held tightly in such a coil.

Replacement string

Dummy pin and stringing crank

The oils that are produced by most peoples' skin can cause piano wire to rust, so I wear these thin cotton gloves whenever I need to replace strings.  I've cut a piece of wire that is long enough to span the distance from the tuning pin to the hitch pin and back plus about 6-8 inches.  This is to allow enough room to make the coils on each end, plus a little extra breathing room.

Start by feeding one end of the wire under the v-bar toward the left tuning pin. The next step is to make the first coil.  To do this, I use a dummy pin (a normal tuning pin removed from a scrap piano) and a stringing crank. Take the end of the wire that has passed under the v-bar and insert it through the hole in the tuning pin so that the end is flush with the surface of the pin.  Make a tight counterclockwise bend (called a "becket") in the wire and use the stringing crank to make two and a half tight coils on the pin.

Making coils on the dummy pin

Pry the becket out of the dummy pin, push the coil onto the left pin, and insert the becket into the tuning pin hole.  Pull the other end of the wire down and make a  bend around the hitch pin of a bit more than 180 degrees. The wire will spring back a bit and the bend should stick at about 180 degrees.  Feed the end of the wire up, under the v-bar again, and past the right tuning pin.

One end of the string has been coiled onto the left pin. The right pin still needs a coil.

Bend the string around the hitch pin.

Measure four fingers' length past the right tuning pin and cut the wire.  Thread the end of the wire into the dummy pin until flush and make a coil until it is at the same height as the right tuning pin.  Remove the coil from the dummy pin, push it onto the tuning pin, and insert the becket into the hole.  At this point, make sure the string follows the same path that the strings around it have already established.  There are several staggered pins above the hitch pin (called "bridge pins") that the string needs to bend around in a specific way.

Measuring four fingers length above the tuning pin

Now the pins need to be turned clockwise while keeping the coils tight together on the pin.  Tighten the right pin first, alternating between making small turns with a tuning wrench and squeezing the becket into the hole with large pliers.  You will also need to pull the coil toward you with a screwdriver or coil lifting tool while tightening the pin, in order to keep gaps from forming between the wraps of the coil.  Keep alternating until the pin has almost three full wraps on it, then switch to the left pin where the same process can be repeated.  Using a screwdriver, adjust the spacing of the strings just below the v-bar to match the spacing of the strings around it.  When both sides of the string are taut, the string replacement is finished and the string can be tuned.  New strings need to be tuned several times before they are "stretched" and will hold a tune for any length of time.

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Kimball Damper Pedal Repair

The damper pedal on my Kimball upright snapped in half the other day.  This is not a particularly common problem to have, and the repair involved some metalworking (which is a field that I suspect most piano technicians don't have much experience in), so it seemed a great candidate for my first blog post.

The repair process involves removing the broken pedal from the piano, cleaning both pieces, brazing them back together, sanding the repair smooth, and reinstalling.  Normally to remove a pedal on this piano, the entire piano must be tipped onto its back to remove the screws that hold the toe board on.  The toe board is the horizontal piece of wood that has square holes for the pedals to extend through.  In this case, the front half of the pedal was broken off and so the back half could be slid back through the toe board and removed from inside of the cabinet.

There are four screws that had to be loosened before the pedal could be removed.  The pedal operates by pivoting on a steel pin that is held on either side by a block of wood.  Also, note the steel wire that acts as a spring to return the pedal to its resting position when downward pressure is released.  Once the four screws are loose, the wood blocks can be pulled away from the pedal, and the pedal can be pulled out toward the top of the picture.

Here you can see the pin that keeps the pedal from being pulled out of the front of the piano while the toe board is still in place. The pin can now be popped out with a hammer and punch.  Removing it will allow me to later reinstall the pedal through the front of the toe board, and then tap the pin into place through the wood blocks and back through the pedal itself.  While I have the pedal removed, I will also replace the felt bushings on the pin that reduce friction and provide quieter operation.

A clean joint is imperative for creating a strong bond while brazing.  I use multiple grits of emery cloth for cleaning up these joints.  Here you can see the clean joint that is ready to be fluxed and brazed.  

I've recently acquired a new brazing system.  I still have my old setup with standard oxygen and acetylene tanks and Smith torch and regulators which I will use for heavier duty brazing and cutting.  The new setup is much lighter duty and consists of a BBQ propane tank, a medical oxygen concentrator, and a lightweight Smith torch.  The main advantage to this system is convenience.  I only have to go 5 blocks to the nearest Walgreens to refill the propane, rather than 12 miles to refill my acetylene and oxygen.

My old brazing setup.

My new brazing setup for light-duty work.

With my joining surfaces cleaned up, I brushed on my "Stainless Light" Silver Brazing Flux from Cycle Design USA and proceeded to fire up my oxy-propane torch.  I brazed the pedal back together with 56% silver (also from Cycle Design USA) which worked fairly well.  

I did end up with a small spot that didn't fill in.  I think the pedal was just a little too thick for this torch to be really effective.  The oxygen concentrator can only put out about 8-9 psi, and I'm still figuring out the right pressure ratios.  It seems the propane needs to be at much higher psi than acetylene does for brazing.  On the bright side, the joint survived my testing, which consisted of holding the pedal on the square end and banging the round end against the table.

Flux applied to pedal.

Pedal after brazing and before cleanup.

With the brazing done, I filed down the excess filler and sanded it smooth with emery cloth.  I then reinserted the pedal through the toe board and tapped the steel pin back into place with the new felt bushings.  I could have applied some kind of clearcoat to the pedal to keep it from rusting, but with the amount of friction this pedal will see against peoples' feet, I think I will just give it a rubbing of mineral oil every once in a while.

Pedal post-cleanup.

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