keyframe bedding

[John Hartman]

Bob Hull wrote:
> Dear List,
> I'm working on a Steinway M regulation and on bedding the keyframe. (Not 
> the same one I had a question on about a month ago.) I thought I had 
> accomplished this already- but the knocking on the bass end has returned 
> during the process of the other regulation steps.  I'm wondering if when 
> I regulated the balance rail studs it came back. I used the sliding 
> paper method and felt good about the results.  So, as I found this 
> knocking I returned to the keybedding and I did some more sanding on the 
> bottom of the front rail but no progress seems to be coming about - the 
> bass end still knocks when you tap on it.  Both ends of the frame knock 
> when tapped, but the treble stops when you put the cheek block on, but 
> the bass end still knocks.  I measured the thickness of the front rail 
> on both ends and the middle.  Bass end is .836; middle of front rail is 
> .881 and treble end is .850 or .860.  I know the keybed is crowne! d up 
> in the middle and the keyframe is reverse crowned.   Here's my question:
> What would you think of painting a layer of epoxy on the bottom of the 
> bass end of the rail to thicken it rather than sanding/thinning the 
> whole rest of the rail until that knocking went away? (The knocking 
> begins about 1 octave from the bass end.)
> Also, with this crowned/reverse crown between keyframe and keybed should 
> the testing of the bedding be always done with cheek blocks screwed in?
> One other question to drown you with - do you reflect the crowned keybed 
> in the key leveling?  I have heard yes and no on this.
> Thanks.
> Bob Hull


Bob,

The proper process is to first bed the back rail with the dags. Then the 
front rail and finally the balance rail. Looks like you're having 
problems with the front rail. Go back and and unscrew the balance rail 
glides (till they don't touch the keybed). Then re-set the front rail. 
Often, because the pins wear out, the keyblocks need to push the 
keyframe pins down harder. If there is a cardboard shim under the block 
see if removing this gets the end of the front rail to seat. If this is 
not enough try shimming the guide pin plates (from above with a slip of 
veneer) to get more pressure. Sometimes installing a new pin or turning 
the pin to a new face can help. Check to see if the pin is tight in the 
front rail. A loose pin can cause a lot of problems.

After you fix the front rail go back and readjust the balances rail.

Let me know if this help. There is a lot to doing this a short e-mail 
cant do it justice.

John Hartman RPT

John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
Rebuilding Steinway and Mason & Hamlin
Grand Pianos Since 1979

Piano Technicians Journal
Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]