Relocating Knuckles

[Overs Pianos]

Phil and all,

>One more question before this thread dies.  What size slot do people 
>cut?  Or in other words, how much clearance do you allow for the 
>knuckle core?
>
>Phil Ford

We use a 2 mm slotting cutter to provide a slight interference fit 
with the knuckle tongue. The original slot is filled prior to cutting 
the new one. With only 20 + mm distance between hammer center and the 
jack/knuckle contact, it doesn't take much of an error to make a 
significant difference in the note-to-note hammer/key ratio.

We use a small milling machine for this work. The head can be rotated 
to any angle, so we set the chuck axis parallel to the table so that 
the jig can be mounted horizontally, and packed up to enable 
appropriate XYZ adjustment between the cutter and the work-piece.

When doing this work, its worth checking that your machine used 
doesn't have axial float. A 2 mm slotting cutter fitted to a machine 
with 0.25 mm axial float results in slots which vary from 2 to 2.25 
mm. Our mill has a cap screw style lock on the rack and pinion quill, 
so its a simple matter to lock it.

I second one of your earlier post Phil. There seem to be regular 
occurrences where technicians rebuild grand actions with off the 
shelf parts which are inappropriate to the job at hand. Often one 
part of a poor-action-geometry fix will involve relocating the 
knuckle slot to 17 mm from 15.5. We've reset quite a few of these 
where the parts were practically new.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:info@overspianos.com.au
_______________________