seeking wood screws

[Terry]

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Hey, ya learn sumptin' new every day. Please tell me more. How does the =
bare nut act as a stress concentrator (and what exactly is a stress =
concentrator). How does a flat washer help distribute the load (if the =
nut was only touching the plate in one spot, it seems that even with a =
washer in there it would still do the same)?

I know sometimes I will pose a question facetiously, but as I do not =
have any background in mechanical engineering, I am genuinely curious to =
hear more on this. Thanks.

Terry Farrell
  ----- Original Message -----=20
  From: Dean May=20
  To: Pianotech=20
  Sent: Saturday, January 08, 2005 12:58 PM
  Subject: RE: seeking wood screws


  It's a throwback to my days as a design engineer. It is bad practice =
to place any kind of stress concentrator against cast iron. The washer =
is a little insurance to distribute the load, though ideally it should =
be hardened to maximize its effectiveness.

  Thanks for the tip on the hole.

  Dean
    -----Original Message-----
    From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On =
Behalf Of Terry
    Sent: Saturday, January 08, 2005 11:34 AM
    To: Pianotech
    Subject: Re: seeking wood screws


    Why do you put a washer on top of the up-side-down lock nut that =
goes on the backside of the plate - assuming of course that the nut has =
enough horizontal surface area to mate with the plate (and not want to =
fall through the hole)? I would just be afraid of a potential =
rattle/buzz if one of the assemblies got a little loose (I realize that =
none should be). I just haven't found that to be needed. I do put a =
washer on the top though - but mostly to protect the plate finish while =
tightening the acorn nut on top.

    5/16-inch hole gives me a nice very snug fit.

    Terry Farrell

      All this talk of screw sources has had me browsing some of these =
sites. Very cool. I've always tried to maintain an organized supply of =
various screw types and sizes which has been a huge asset. But it is not =
always easy to get big boxes of the sizes you want any more. Most places =
only sell the little 15 piece plastic packages (very expensive way to =
buy screws).

      Anyway, I have been wanting to do the plate suspension trick for =
adjusting downbearing. Del spoke of it at the recent Indy conference. =
This involves threading socket cap screws (headless bolts with recessed =
allen socket) into the inner rim, running down a lock nut upside down =
with a washer on top (a sufficient clearance well counterbored into the =
soundboard), the plate lowered onto the washer, a chrome washer and =
acorn nut on top. The height of the plate can then be easily raised or =
lowered by removing the acorn nut and turning the stud with and allen =
wrench.=20

      Attached is what I ordered. I got the hanger screws just for fun. =
If the machine thread doesn't work well, which Del said it would thread =
right into the wood, I can always fall back on the hanger screws with =
their lag thread.=20

      Does anyone have a recommended hole size to drill the rim for the =
3/8" machine thread to screw into?

      Blessings,

      Dean

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