plate crack

[rsnelson]

---------- Original Message ----------------------------------
From: Ron Nossaman <nossaman@SOUTHWIND.NET>
Reply-To: pianotech@ptg.org
Date: Fri, 8 Oct 1999 11:08:58 -0500 (CDT)

>>If this new method you mention is Lock-N-Stitch pins it is not a sure fix
>for piano plates. I've had enough experience with it that I would not use it
>by it self to repair a crack in a plate. I would be happy to discuss this in
>more detail if the group wishes. 
>>
>>Richard O Snelson
>>Oliver Piano Services
>>
>
>
>
>By all means.
> Ron N
Ron and group, 


I found that the pins work well in the demo when they are fitted into  flat pieces of steel or cast held in a vice. With a piano plate nothing is flat! The crack faces are sloped! To install the L-S pins it's necessary to first drill a hole and then spot face a surface into/around the hole for the shoulder of the pin to sit in. This is very tricky with a piano plate because of the curve of the surfaces. The spot face will tend to shift to one side as you use it. This results in a L-S pin that will not hold anything. The pin depends upon the spot face being 90 degrees to the axis of the pin.  I have used the pins on several repairs. The first was a 5" crack on the back protrusion of the plate casting. I installed about 40 pins along the crack. I had it held together with a large sheet of alum riveted to both pieces.  The two pieces fell apart in about 2 seconds when the alum was removed.  I had several talks with L-N-S about this. They admitted the need to use extreme care when drill along a shoulder or when the surfaces are not level. 

My second repair came out a lot better. I made steel plates to fit on the sides of the plate struts.  I then attached them to the strut with L-N-S pins. The pins break off when the shoulders seat. You can then grind then flat so they don't show. I didn't stop there however I stitched the steel plates to the cast with high nickel rod. This made a repair as strong or stronger that the original cast. 

I will mention that to get set-up to use L-N-S pins is not cheap. You need special, spot facers, special drill bits, special taps and they buy the pins. All this is around $400!!!!!!!!!!!!! The taps, spot facer and drills don't hold up well..... I needed to replace several of them on the repairs I discussed. If the cast material around the plate crack has been previously welded "Give up trying to drill it" Cast becomes very very hard welded. That's part of the reason that cast welds don't hold well. 
I will be gone this weekend but would be glad to discuss specific repairs on Monday when I return. 


Richard Oliver Snelson
Oliver Piano Services
http://www.oliverpianos.com
(soon to be full time, 54 days can't wait)

retiring from 
Engineering Dept, 
Illinoi Power Company