The Care and Feeding of Pin Blocks #1
On one wall in my shop, in plain sight of all who enter is my Wall of Shame. On it are examples of what not to do to a pinblock. After several recent conversations with other techs and clients as to what can and cannot be done to save their old blocks (PB), I thought it may be worth while to share these thoughts with the larger community. Some may disagree with my observations and hopefully a enlightening dialogue would ensue.
When the torque gets so low that it either becomes difficult to set the pin or the pin will not hold at all there are several remedies which can add a few years to the PB or speed its demise.
First determine possible causes for the loose pins. Mark all marginal to completely loose pins. Often you will find they will congregate along the flange in the bass and low tenor. Inspect the bottom of the PB. While for the vast majority of pianos the tuning pins never reach this far it can give some idea as to the condition of the PB on the top layers.
If a line of pins is loose along the plate flange this doesn’t necessarily mean you have a crack. It could be just an excessive amount of crushing of wood fibers between the tuning pin and plate flange. However caution should be exercised. A line of loose pins within the tuning pin field however is usually a terminal condition. It usually indicates a crack either in the grain of a fletch or a delamination somewhere in the block. Any repair with this condition is temporary at best and in all likelihood would simply spread the crack further through the block.
If the loose pins are random or involve nearly all of the pins in a given area and there is no evidence of contamination with of some witch’s brew of PB restorer there is hope yet.
The first effort would be to drive the pins a little deeper in the block. You don’t necessarily have to drive them very far, sometimes just tapping the pins so that the threads of the tuning pin cross the threads in the block will increase torque sufficient to make the piano tunable. However if you must drive the pins further be sure to keep the coils off of the plate. Contact with the plate can lead to broken strings or you may actually drive the pin up when the pitch is raised and additional string is pulled onto the pin.
If there is sufficient room in the plate hole, a larger pin can be used. Generally you will need to go up two sizes to get sufficient torque. As you drive larger pins be aware of pins loosing torque elsewhere in the piano. This would indicate either a spreading crack or you have more loose pins than you realized.
Now we come to my wall of shame. Residing in a place of prominence is an example of what will happen if you don’t support the PB when you are driving the pins. The entire bottom layer is delaminated in the tuning pin field. The doer of this deed knew what they had wrought for there are many small brads nailed into the perimeter of the field. The harp of this particular piano came out before the action as there was no way to get the action out from the PB.
Today we looked at mechanical repairs, next time we will examine various chemical repairs.