How to make a piano keyboard

Step 16 Bench regulating: action

I fitted the action brackets to the keyframe so they were square and located the holes for the mounting screws for using transfer punches and drilled them by hand. I had to file a little at the front of the ledges on the brackets so that the underhammers and hammers were in the proper mechanical arrangement with the hoppers and keys. The hammer rail is also supported in the middle by a stud that passes between two keys and is fixed to the middle stretcher, I used transfer punches to locate the necessary holes as well.

Then I rough regulated the action. Piano tuning teacher Oliver Faust gave instructions for regulating the "old English square" action and illustrated one made in Boston in the 1830s, but I didn't end up following them very closely. I set it with about 1mm lost motion between the hoppers and underhammers, enough that the keys could return to rest even moving slowly, by moving the underhammer rest rail, which is the unmarked narrow piece screwed to the underhammer rail in Faust's picture. I adjusted the heights of the hammers above the underhammer rail by a little more than the thickness of the cloth strip that would be glued between them by either filing or gluing shims on the bottom of the wedges depending if they were too high or too low. I adjusted the hoppers so they flipped out from the underhammers when the hammers were a little short of the height of the strings above the key bed. When the hammers reach this height my keys go down a little over 8mm.

I removed the rails, and relieved and clothed the ends of the keys for the damper levers which meet them at angles. I pressed in the backcheck wires and glued on their coverings, and then set the key dip to 8.5mm, both by adding paper punchings on the front rail and by gluing a cloth strip the right thickness to the bottom of the underhammer rail. A gauge block made as thick as the required key dip and with a lip kind of like the cauls for gluing ivory is helpful selecting the right punchings.

At this stage in a factory the keyboard and action might be reassembled and delivered to another department for trimming and finishing. I haven't reached that step yet.