Pianoshop :: Info :: Figures :: Key Dip
"Key dip" is the distance that the key travels downwards when played. It is usually 10mm on modern pianos. Some older pianos, particularly French models, have a smaller keydip. Over the 10mm of travel, the action has to raise the hammer to the strings, throw the hammer at the strings, release the jack from underneath the roller and catch the hammer on its way back down. The actual process of making the sound takes about 9mm of key travel and the other 1mm is the "After Touch" which is important for hammer "checking" and has a surprising influence on the feel of a piano.
The key dip is adjusted by adding or subtracting cardboard washers from underneath the felt "Front Rail" washers (baizes). The picture below shows a close up of a front rail with one of the baizes lifted to add cardboard washers.
Below is a picture of keydip being adjusted. The three jars contain cardboard washers of 1.5mm, 0.5mm and 0.3mm. The wooden block and washer on one of the white keys is a "Key Dip Block" 10mm deep used for measuring and adjusting keydip.
