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- Key Balance Hole Repair
- March 1997, Piano Technicians Journal
By Newton Hunt, RPT
- Key chucking, the fore-and-aft movement of a key, causes noise and changes the key's contact point with the wippen and, therefore, changes the action geometry. This movement can be felt by pianists and is most disconcerting. There are a number of repairs for this condition:
- Steaming to swell the wood,
- Glue-sizing the hole,
- Using a thin blade to cut a kerf and insert a piece of veneer,
- Using fiber inserts,
- Enlarging the hole and replacing with new wood.
The first three are very useful, effective and quite simple and fast. Next to last is an old procedure fraught with many problems, which leaves us with the last item. When the holes have become so enlarged or damaged that the first three will not realize a proper fit, then more radical surgery is a necessity.
Ralph Onesti, RPT, sells a set of tools which makes this repair sure, accurate, reasonably quick and of a high quality. There is a set of 25 graduated round feeler gauge/guide ins, a cutter for the keys, a set of keypin-sized drill bits and a large plug cutter. The procedure is quite simple.
Using the graduated gauge pins, sort the keys into sets where a given guide pin will fit into the balance pin hole just a tiny bit snug. The corresponding gauge pin will become the guide pin for the respective key group.
You may wish to write the gauge pin letter on the key to prevent confusion later.
If there are keys with massive damage so that a gauge pin will not center in the hole, the key can be placed in the keyframe with neighbors to align properly while sitting on a snug fitting paper punching of .015" or greater glued onto the bottom of that key. This will provide an adequate guide for the pin and cutter. Selecting the proper drill bit for the size of the balance pins, insert it into the plug cutter, centering properly.
Select some nice wood with a close grain such as poplar, soft maple, lemon (naturally lubricious), walnut or a hard pine like old yellow pine, cut thin slats about 3/16" thick by 2" wide. Using the plug cutter, cut ninety or so wooden washers.
Select a piece of wood slightly wider than the keys and clamp this into a drill press vise at the same angle as the balance rail pin is to the key when half depressed. Set it into the vise as deep as possible so the jaws of the vise provide a cradle for the key.
Select the first group of keys with its attendant gauge pin. Insert the pin into the key cutter, tighten the screws and chuck it into the drill press and check that the keys will fit under it and the cutter will not hit the vise jaws. Set the depth of cut so that the cutter cuts a nice notch in the shallow part of the cut. The guide/gauge pin will center the key (having some free movement) and the cutter will cut out a circular recess in the bottom of the key perfectly centered and sized to receive one of the washers previously cut.
With some hide glue or Titebond TM, put some glue around the edges and flat areas of the cut in the key and snap a washer into the key with the grain running parallel with the sides of the key.
Use a sharp knife or chisel to remove most of the excess material, and a router with a trim bit to finish the sides of the keys to a perfect trim. With a minor setup on a router table, the excess material can be removed to form a perfect bottom for the key.
Ease the new wood until the key slowly returns to rest from a lift of the front with enough weight at the capstan to lift the front of the key to its rest position. A perfect fit, capstans, key fronts and key ends in a nice straight line. If one does happen to be out of line, enlarge the hole and glue on a punching and re-cut the key. No problem.
NOTE: The tool is made so efficiently that its use does not necessitate heavy power equipment or a shop facility in order to effect repairs. All that is needed is a small, tabletop model drill press. In an effort to demonstrate this we offer an event that took place at the Kansas City Convention in 1994.
A hands-on technical class was in operation and keys from action models were used so much that they had become worn passed their usefulness. Ralph was called upon to use his system to restore the balance hole configuration. An available drill press was used and some chisels and sandpaper from Kevin Leary's class. Although this is not the equipment one would want to use on an entire set of keys, it was easily demonstrated that even the most sparse equipment could be utilized to effect repairs with this system.
The May 2003 issue of the Piano Technicians Journal again references this system in the Q & A Rountable. Newton once again noted its superior quality and accuracy, derived from his repeated successful experience with the tool. The following is quoted from that Roundtable discussion:
The advantage of Onesti's system is that you use the pin that fits snugly in the hole and use that pin to guide the cutter. I use the back of the hole as a place to pick up the pin size. I felt, with my limited vision, that Onesti's system would be more foolproof.
Newton Hunt's untimely passing in November of 2002 has left a void in our profession. His dedication and contributions to our industry will long be remembered.
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