CA gluing Grand Pinblocks....My take on it/ Richard Brekne

[Joe And Penny Goss]

Hi Ric, Any hair left<G>
Joe Goss
imatunr@srvinet.com
www.mothergoosetools.com
----- Original Message -----
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: <pianotech@ptg.org>
Sent: Wednesday, July 31, 2002 2:18 PM
Subject: Re: CA gluing Grand Pinblocks....My take on it/ Richard Brekne


> Keith Roberts wrote:
> >
> > Richard,  the shear force of scissors is two forces that are parallel
but
> > opposite and they shear the hair off which is at 90 degrees to the
forces.
> > Nail two blocks together and move them sideways and the nail will shear
off.
> > The shear strength of the nail is at 90 to the nail. Shear wind is at 90
to
> > the direction of travel of the airplane. The string pulling the pin
sideways
> > trying to cut the top off the pin could be called a shear force. Hard to
> > explain but did I make it clear enough?
> > Keith R
> >
>
>
> Ok... obviously either I have misunderstood the concept of
> shear force, or something else is wrong with this picture.
> Tho the scissors exert a shearing force on an object, does
> the object being sheared exert a shearing force in return ??
>
> "Definition: A force that acts parallel to a plane rather
> than perpendicularly, as with tensile or compressive force."
>
> I have never thought of shear force in this fashion, tho of
> course I have heard of "shearing" off a nail, and the
> likes.... but I wonder this is actually the same thing as we
> are talking about. In our example of the string exerting a
> shear force on the bridge pin, the bridge itself on the
> other side of the pin have to be the "other half of the
> scissors" so to speak. While this exacts a shearing force on
> the pin itself, I am confused about how the same can be said
> for the two arms of the "scissors". The bridge should suffer
> from the results of the pin being pressed against it. This
> speaks of a compressive force on the bridge to me... or what
> ?.
>
> Attempting to cut a rigidly held nail with the average pair
> of scissors, or a cheap pair of nippers will result in dents
> in the blades .... at 90 degrees to their cutting planes....
> isnt this the result of compressive force exerted on the
> blades ?
>
> Shear stress between two surfaces of the bridge pin and
> bridge would have to be a result of whatever force was
> either pulling up, pushing down, or twisting the pin against
> the ability of the tightness of the hole to resist the pin
> moveing. Right ???
>
> Thanks muchly for your thoughts... but I am still scratching
> my head... grin.. what else is new eh ?
>
> Cheers !
>
> RicB