Earlier Steve Turadek wrote,

> but then you point out that user-pressure won't deflect a smoother quite so
> much.  true.  and also we're pretty much disregarding the fact the sole may
> be *twisted* instead of simply concave, front-to-back.

   I'm assuming no twist.  Thinking in terms of the symmetry of the
   plane body, the left and right sides are gonna deform after 
   manufacture in a similar manner, unless there's something unusual
   about the metal, or the plane body was cast assymetrically.  So,
   while twist may be there, it's gonna be just a small fraction of
   cancavity along the plane's length, methinks typically for a plane
   of any quality.

   ( Anybody seen otherwise?  It could happen... )

   Wooden planes are a different story, though.

> I think the way the
> plane is constructed, you've got a heavy frog tending to resist any user
> pressure in the short axis of the plane (but also trying to flatten it in
> that axis as well.)  this is all getting complicated.

   You have to break the problem down into small pieces, then it's 
   not so hard.  ... For the #8 I'm ignoring the frog, because it's
   only a tenth the length of the plane.
 
> back to the original example.  okay, you've got an gross concave surface
> and user pressure holds the center flat to the work.  but how much pressure
> is exerted against the work *at the mouth* after this deflection is
> flattened out?  in the example given: 0.  in effect, the mouth has *no*
> effect.

   Any pressure _above_ the straightening pressure will apply to
   the mouth.

   BTW, in case you haven't yet guessed what's next... :  Wood deforms
   as well.  As you apply pressure to the ( assumed concave ) plane,
   the areas at the toe and heel in contact with the wood will compress
   the wood downwards, thus lowering the overall height of the mouth
   above the wood, and reducing any amount of flexure required to
   maintain mouth contact.

> anyway, personally, I don't have any planes this far out of tune, so I
> can't speak to how well they do or don't perform.  I have had planes with
> unflat bottoms and I've tuned (flattened) them and they seem to work
> better.  I haven't done this with a #8, but I've done if with a couple of
> modern blocks and have found them vastly improved.

   Ah, the block plane!  Now that's a situation where flexure will
   approach being negligable, and things like compression of the wood
   at either end of the plane ( to approach mouth contact ) will start
   to take over.

   Doug Dawson
   dawson@p...

   Just say, I'm not a flat-soler, really I'm not! etc.