[TheForge] engineering question

[Justin Fellenz]

Maybe the whole point here is to use a square tenon, not to find the
strongest joint. But I gotta go with Rick. The problem with a square
tenon as I see it is that regardless of its orientation it introduces
sharp angles where stresses can concentrate. In m&t joints where the
stress is rotational like in the right-angle joints in a parallellogram
table or compression-tension like in a diagonal  brace--which is most
of them--the breaking force attempts to tear the mortised piece apart
transverse to its axis. A square tenon gives sharp angles on this axis
that need to hold up against the entire moment arm of the tenon piece
(rotational) or one or both of the moment arms on either side of the
joint in compression/tension (there's a vector problem there....)
Either way, they're a nice place for the metal to tear.

But like I say, maybe the whole point is to use a square tenon.

For what it's worth then. Physics geeks?

JRF

ps. who's got a press? 

--- RICK KORINEK <rickkorinek at rcn.com> wrote:

> How about using a round tennon to put the piece on the 
> diamond?
> 
> 
> ---- Original message ----
> >Date: Sun, 3 Oct 2004 10:33:05 -0400
> >From: "Walter L. Mullett" <wmullett at bright.net>  
> >Subject: Re: [TheForge] engineering question  
> >To: "Sponsored by ABANA" <theforge at mailman.qth.net>
> >
> >I think the diamond puts the corner closer to the edge since 
> the diagional
> >is longer than a side.  I think the diamond also introduces 
> a stress point
> >at the wrong place.  When you look at the forces as they 
> flow trough the
> >object, the square would show less stress.
> >  |         |               |         |
> > / _____ \             /     /\    \
> >/  |       |  \           /    /    \    \
> >|  |       |   |         |  <        >  |
> >\  |____|  /           \   \     /    /
> > \           /             \     \/    /
> >  |         |               |         |
> >
> >-----Original Message-----
> >From: Mike Linn <bamablacksmith at comcast.net>
> >To: Sponsored by ABANA <theforge at mailman.qth.net>
> >Date: Friday, October 01, 2004 7:43 PM
> >Subject: Re: [TheForge] engineering question
> >
> >
> >>
> >>I would say on the diamond would be stronger because on the 
> square would
> >>put the corner closer to the edge. and thus thinner, though 
> I think the
> >>difference would be minor depending on the direction of the 
> forces.
> >>
> >>
> >>mike
> >>
> >>
> >>
> >>At 01:51 PM 10/1/2004, you wrote:
> >>>In slitting and drifting a square hole,
> >>>since no metal is lost,
> >>>will it make a difference in strength if the hole is 
> square to the side
> >>>or on the diamond?
> >>>
> >>>
> >>>dan tull
> >>>georgia
> >>>abba, afc, S.C. psba, obg,sofa
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> Rick Korinek
> Emerald City Forge
> Framingham, MA
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