Having discussed section I, The Keys & Keyframe, last week, we will continue with section II, The Top Action. Note that those procedures covered recently elsewhere such as rebushing, steaming warped keys, repairing the balance pin hole, etc., will be skipped over in this guide to regulation.
15) Check action centres, repin or shrink as needed. There are many tests which can be used to determine if the action centres are too tight or loose. Lets discuss the hammershank / flange centre first, since it’s by far the most important and the most troublesome. I will list the six checks I regularly use for this centre:
A) Wiggle each hammer gently side to side and feel by hand if the centre feels loose. B) Similarly, insert a long screwdriver blade under the shanks and wiggle the blade from side to side. Watch the hammer for any sign of lateral movement. Any movement indicates a loose centre. C) While the screwdriver blade is still under the shanks, lift all of the hammers in a section up and quickly release the blade downwards. Any sluggish centres will be late in following the blade down. D) With the screwdriver still under the shanks, block the blade up at both ends so the shanks rest on the blade, preferably right on top of the rest felts/rest rail area. Individually raise the hammer and let it fall on the screwdriver blade. Listen closely to the sound upon impact, and watch how much bounce the hammer takes. Too little bounce indicates a tight centre. A noisy impact of the shank upon the blade indicates a too loose centre. This noise is much like striking a baseball bat upon the concrete and listening for a crack in the wood. E) With the action firmly in hand (preferably screwed down to the keyframe) put the action on one end and swing the hammers out away from their rest position and back. Any sluggish centres will be noticeable by the lack of movement. F) And, of course, the best method is to unscrew the flange and check the swing of the hammer by hand. Take the flange in one hand and hold it vertical, the hammer being taken by the other hand and raised to a horizontal position, 90” from the flange. Holding the flange very still, release the hammer and watch how many times it swings under the flange. This will look much like a pendulum. Count the number of passes the hammer makes under the flange. For this centre, seven or eight passes is considered excellent. If the piano is a Steinway with teflon bushings, then the best results are at five or six passes. Fewer passes indicate a sluggish centre or a bent centre pin. Greater than eight passes indicates a loose centre or some other problem such as a crack in the shank at the bushing area.
This is not as much work as it sounds. Just make sure the hammers are all properly spaced to the strings before you begin, and the whippens and backchecks are aligned to the hammershanks and tails. Take off all of the odd numbered hammers and work on them. Replace them and realign them using the neighbouring hammers and the previously aligned whippens and backchecks. Go on to the even numbered hammers and complete the job in the same manner. Recheck the hammer to string alignment and you are done.
I highly recommend using a pin vise which is capable of extracting and installing centre pins. If you work on Steinway teflon bushings very much you will notice the extractor pin is a little large and often ruins the teflon bushing while .removing the old pin. Just remove the extractor pin and turn it down, using a drill and wet/dry sandpaper.
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