Body Parts On A Piano?

It's Technical Tuesday & we're back after a short hiatus!  Today we'll be talking about 'Knuckles' and 'Butts'.  Body parts, you say?!?  Let's explore this a bit.

The same component in both a grand piano action and a vertical piano action has two different names.  On a grand piano it's the 'Knuckle'; on a vertical piano it's the 'Butt'.  

This small component is located at the lower (larger) end of the hammer shank, and rests atop the jack which controls the velocity of the  movement of the hammer from its resting point to the point where it strikes the string.  The velocity of this movement is determined by the speed and pressure applied to the piano keys by the player.

The Knuckle

On a grand piano the knuckle is attached to the underside of the hammer shank near the hammer flange.  The knuckle is small and round in shape, traditionally covered in buckskin.

The Butt

On a vertical piano, the butt is located directly on the end of the hammer shank.  A modified square/rectangular shape, the butt is also configured to rest on top of the jack.  Just like the comparable knuckle on the grand piano, this is also traditionally covered in buckskin.

Note: Pictures in this posting were taken of piano action models to allow for close-up, detailed views; and were taken of both traditional wood actions, as well as composite actions.

Next time, we'll take a look a the hammer shanks.  

"The Disclaimer" - Technical Tuesdays are intended to give folks who are curious about pianos a bit more understanding of all those technical terms thrown about by piano technicians.  This is not intended for super in-depth technical analysis, nor micro measurements; just general knowledge for those who are interested in how a piano works.