Korean Dip

[Roger Jolly]

Korean DipInteresting topic.  Key dip, after touch , and what I call the sponge zone. Is very interactice collection.

Now 10mm dip is a very common parameter for grand dip. After touch, can vary greatly depending what is going on in the sponge zone.
Many Korean grand's have a balance rail hole that is in the 5-7mm range of height.

My research has shown that a spruce, or basswood key needs to be 4mm max for height.  Maple shoed keys need only be 3mm.
These heights give an adequate safety factor, with regards to wear, and eventual pulley keys.


With a tall balance rail hole, the key starts to bind before escapement occurs, after touch will appear to vary from a very soft to a firm touch. A little under 4mm BR hole ht. .015" after touch is usually attainable. A 7mm hole you will need .050 to .060" of after touch to get the piano to feel right.

Some of the older Samick key boards reaming the mortise from 7mm down to 4mm will result in dip going from 11mm to 10mm.

Moral of the story. Measure and correct the balance rail holes before refining dip and after touch.

Now I'll crawl back under my rock.

Regards Roger.

PS  37 steps should be 1 37 steps in some cases.
  



  ----- Original Message ----- 
  From: Alan Barnard 
  To: pianotech at ptg.org 
  Sent: Wednesday, January 30, 2008 4:30 PM
  Subject: Korean Dip


  The subject line does NOT refer to any recipe made with kimchi and sour cream; nor does it refer, at least not directly, to any geeky little man from South Uijeongbu.

  Rather it is this: I'm working on a Hyundai grand. Anyone have a key dip measurement for these? It seems to be about 10 mm which is a littler deeper than 3/8"

  Who actually makes these pianos? I assume it's from China.

  Alan Barnard
  Salem, MO
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