Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Is it bad to tap-in a pin?

My own 29 year old upright has a couple of treble pins that move with only the slightest hint of lever pressure. Is it an acceptable practice to increase pin stiction by slackening the string then giving the pin a light tap with a pin punch before retuning?

Ian

It is a better idea to call a professional technician
to do the fix. Since you have several treble pins that are loose the piano pinblock should be evaluated. Perhaps it is an environmental issue at the root of the problem with low humidity causing the wood to shrink and loose grip. Tapping the pin can be done but shimming it or using a larger pin may be better options. I would recommend having a tech come and take torque wrench readings of the entire piano and then develop a repair plan. TaPPING THE PIN CHANGES THE PLANE OF THE STRING AS WELL AS DISTANCE THE STRING COIL HEIGHT TO THE PLATE. YOU COULD OVERLOAD THE STRING AND BREAK IT

If the pin coils are not too close to the frame, you could tap them in as long as you're careful in leaving clearance. There is no need to slacken the strings off before tapping them in they'll drop automatically. It's very much a quick fix that may help the odd loose pin,but worth trying before contemplating other established options. Normally treble strings aren't so much subjected to the dangers associated with breakage doing this as are the bass, where a cute angles occur.

I don't like to tap in oins. I prefer applying CA.

Greetings,
It doesn't hurt to tap a pin in, but there is a tool specifically for this. Without it,the string will drop flat enough to destabilize, and/or, you will hit the adjoining pins and damage them. The concern with tapping in a pin is going too far and sinking the bottom of the coil below the surface of the pinblock or plate, which will increase the chance of it breaking. Not knowing what kind of piano this is, it is unknown if the hole is drilled deep enough to allow this. If the hole wasn't originally deep enough, the bottoming out of the pin when it was originally strung could be responsible for the looseness, now, as the pin stopped turning in originally, and began stripping the wood threads that formed around it.

It is also possible that the hole was drilled too close to the plate, leaving metal on metal contact. This usually ruins the hole, and when the metal finally grinds itself some clearance, the pin is loose. I found that to have happened on a Steinway D at Vanderbilt about two years after it was bought, (new!). Nothing to do but plug the hole and redrill.

I think I would favor wicking in some thin CA glue, first. Then all the other stuff can be tried.
Regards,

I'm with Ed and Gadzar. I'd try careful wicking in of water-thin CA glue first. It's less 'invasive'. Times and techniques have moved on.

But as Jimbob points out, there are issues that need to be competently explored here. It seems strange for a 29 year old piano to have loose pins in Scotland, where humidity is never all that low - unless the piano is in a very dehumidified room?

Basic reality check: This is how the pins were installed in the first place at the factory. So, there's nothing really wrong in principle with tapping in a pin. No, you don't want to bang the pin down so that the coils are touching the plate or tuning pin bushing. And no, you don't want to tap in a lot of them in a grand without supporting the pinblock. (Especially an older grand). And yes, it is best to use some sort of tool as a punch so that you aren't hitting directly on the pin -- although it is not essential for a few taps. And yes, if there is a pinblock failure, it might not do any good. But fundamentally it is OK and there is no essential need for professional involvement.

CA is good. It is another perfectly legitimate approach. The two approaches are not mutually exclusive. I have used CA and then tapped in order to achieve adequate torque resistance. CA has functionally replaced all the other brews and potions as a material to help strengthen the pinblock and increase torque. It will also be perfectly useless in the event of pinblock structural failure.

In fact that's actually the diagnosis of PB failure: if these mild, non-invasive approaches don't work, more extensive approaches will have to be explored.

My thanks to all for your replies. I asked the question after reading here about applying CA and thought it strange that pin tapping had not been mentioned as a first line approach. Now I see the negative issues.

I am competent working with mechanical devices and tools from micro drills to cutting metal threads, and thanks to many folk here to working on my technique of maintaining my upright piano.

To understand a little better about pin tapping. When tapped is the pin more likely to jump a thread or more likely that an intermediate thread will be started?

Ian

There is no mystery about driving wrest pins in using a hammer - every piano ever made has their pins hammered in. The threads are mainly there to enable removal, and the question you ask regarding 'jumping or cutting an intermediate thread' don't really have any cause for concern. Providing the pin has not bottomed, tapping in lightly will move it easily, if it doesn't then the likelihood is that the hole is blind and has no further room for the pin today's move... In which case stop, or you may end up seriously damaging the block.

The threads are very shallow. There is no groove jumping IMHO. You are just increasing the surface area in contact with the wood. Also the bottom of the hole will be narrower and grab better.

One interesting note: I once removed pins from a very old european piano. I turned and turned. The pin didn't come out. I'm thinking, what the heck is going on. I get some vice grips and wrench the thing out.

The threads were concentric. Not helical. No amount of turning would have ever gotten that pin out. Isn't that crazy?!

Yes!

Mark - did you check that these wrest pins on the old European piano weren't in fact tapered ? You don't come across many these days but tapered pins were used (and still used on some harpsichords ) whereby removal is done by extraction rather than unscrewing.

Mark,
I had been interested in your comments in another thread regarding "moving the foot" In the case of these problem pins I found it impossible to feel and control pin windup (as I call it) without the foot moving every time.

Ian

When you first apply force to the pin, the pin bends and twists before the foot moves. This is fact. In your case it may be small because of low friction, but it's there.

This bending and twisting can effect a minute pitch change if you have set up the proper situation.

Also, for any specific foot orientation there is a window of 20 cents where the pitch is stable!!! I know because I've measured it. That means the need to move the pin foot is not as critical as we may have thought.

Your job is to get the pinblock friction up. Tapping, ca glue, larger pins, whatever works.

This is the kind of statements that seem unacceptable coming from a piano tuning teacher.

20 cents!

It is much more than that in the low bass and much less than that in the high treble.

It changes from piano to piano. There are grands with lots of friction in the understring felt where you can even move the foot of the pin with no change in pitch. There are old uprights with tired pinblocks where pitch changes when you take the tuning hammer off the tuning pin. In this case the stable window is practically 0 cents wide.

There is no such a thing as a 20 cents window!

Mark, A little off my topic but with your measurements how can you tell whether it was the foot or the nsl that moved? (newbie here)

Ian

The foot didn't move. This is what I did. Anyone can repeat this experiment easily.

Set up an ETD to measure cents.
Mute so a single string is free.
Place lever on pin.
Gently bend the pin toward the string. No twist. Not much force is needed. Watch the cents drop. They will drop about 10 - 20 cents.
Remove lever. Cents will come back up a bit.
Play multiple hard blows. Watch the cents, they may come up a bit more.
Note the cents reading.
Bend the pin up gently until the cents begin to rise 10 - 20 cents. No twist.
Remove lever. Watch cents drop.
Play many fff blows. Watch cents come down. Keep playing hard blows until the cents don't fall anymore.
Note the cents reading.
The difference between the two measurements will be 15 - 20 cents. Isn't that crazy!?

Note: The actual bending force needed to effect a pitch change is very small for short NSL. So, if you are uncomfortable bending the pin too much, try the shortest NSL; pitch will be very sensitive.

But Mark,

The 20c window, according to your test procedure is not a stable window. We all can, and have, ineffectively changed the pitch by too much flex...resulting in a lovely unstable setting. In your experiment, the pitch returned back to or close to the original zero point. This means the stabile window is significantly less than 20c...would that it were so, but 20c it ain't.

Greetings,
I believe it was some years ago that either Jim Coleman, Ernie Juhn, or another of our esteemed legacy members, demonstrated the difference in the foot and top of the pin. It was done by drilling a hole in the bottom of a tuning pin so that a bent wire could be installed as a pointer, after the pin had been driven into a block. The pin could be felt to move in the block before that wire indicated that the bottom of the pin had also moved. I don't know how much of a window this would allow, but it certainly demonstrated that with a tight block, the foot remained stationary while the pin rotated enough to change the pitch.
Regards,