Earlier Jeff wrote,

> Doug Dawson wrote:

> ~  It's been a slow day on the oldtools list, so I had to fill out
> ~  my dinner break with _something_... :-)
> ~
> ~  So far we have a concrete estimate by the ISO of acceptable standards
> ~  for plane sole flatness.  As far as I know, the derivation of that
> ~  standard did not take into account sole flexure, i.e. bending of the
> ~  sole of the plane under downward pressure applied to the plane,
> ~  through the tote, while planing.

> Now this is something new! Standards as estimates.

   It is one point of view, a way of looking at a plane sole, that
   someone might take whose mind wished to come flatly to rest after
   just a little ways. :-)

> ~  It's not hard to get a reasonable idea of what effect that would
> ~  have, for a cast iron bench plane, using standard structural
> ~  analysis foo.  The exact analysis allowing for precise shape and
> ~  so forth is tedious, but we can get a reasonable ballpark figure.
>
> What is a "Ballpark" please?

   A ballpark estimate is an estimate of something, the estimated
   value of which is "in the same ballpark" as the actual number.
   An allusion to Our National Pastime, hitting balls in a baseball
   park.  But as Ollie North said, Nicaraguans don't play baseball...
   Just say, not wildly off.

   And note again, I was estimating the _maximal_ deflection you'd
   likely ever see.

   [ tamp, and tamp of my original post on this... ]

> Messing about, plane in hand, with bathroom scales on the bench top
> (to examine another theory), I found that with my puny 11 stone (154
> pounds) I can register about 90 lbs on the scale. According to Doug's
> figures, this makes a deflection of about 180thou or 0.18 inches. Cor
> blimey! Cor luv a duck!

   I'd made a typo in that _original_ formula, which I corrected to
   the list later that day.  That figure should actually be a quarter
   of what I originally wrote, or 1/32" in your example, again as an
   estimate of what you'd see no more deflection than.  If you tried
   the experiment of doing this, i.e. the setup as I described, I
   expect you'd likely see a deflection which would be a significant
   fraction of that.

   [ tamp ]                                                             
 
> Of course we should pay tribute to this static analysis. What I wonder
> would be the outcome of an analysis of the dynamic situation, taking
> into account of the need progressively to adjust (no split infinitives
> here, no siree) for temperature rises. To what extent does suction on
> non-corrugated soles affect this deflection, one gently enquires?

   I was wondering if you could describe what you mean by static versus
   dynamic in your useage.  I know what they mean, but I want to make
   sure we're talking about the same thing.

   ...  Temperature rises: possibly a factor, to the extent that you
   had differential heating, i.e. one part of the plane body a
   significantly different temperature than the other, which might
   result in some warpage you might or might not need to take into
   account.  But cast iron is a _reasonably_ good conductor of heat,
   so a large component of the effect of heat would be uniform over
   the plane body, and so an unlikely culprit in any deformation.

   ...  Corrugated soles: not so much of an effect, on raw deflection,
   given that the resistance to deflection mainly comes from the sides
   of the plane.  Suction?  We could estimate it to get it out of
   the way...  I'm assuming a smooth-bottomed plane at the moment
   for the sake of concreteness.
 
> However, from where does the ISO's Chief Savant derive this concept of
> /natural/ concavity (undefined in extent) of a plane sole? Observation
> and testing of a statistically significant quantity? Workshop lore?
> Exchange of data at one of these swapmeets one reads about? Mind you,
> most of us from time to time can get preoccupied with certain
> concavities, and convexities for that matter, especially when
> well-dined on a Sunday evening.

   Assuming that a plane sole is not twisted, which in a properly
   constructed plane would be a secondary effect next to curvature
   along the length of the plane, you have three things that could
   happen:  1) The plane sole could be perfectly flat.  This case
   is moot.  2) The location of the mouth ( vertically ) could be
   _below_ the plane occupied by the heel and toe.  This is convexity,
   which we're not considering at the moment, but may later.
   3) The location of the mouth could be _above_ the plane occupied
   by the heel and toe.  This is the situation of concavity that
   we're currently discussing.  ...These three cases are all there is.

> Perhaps next time Doug is well-dined, he might favour us with his
> formula for natural concavity, no doubt including factors such as age,
> (the plane not the owner!) nature, location and area of patent marks,
> length, presence of a complete decal (whatever that is), whether it
> has a low or high knob, factors for rosewood and otherwise, japanning
> percentage, whether bedrock or not and so on. Minor factors such as
> mis-match of knob and tote patterns can perhaps indulgently be
> excused.

   I'm assuming that you have a plane that is concave.  I don't give
   a dog's breakfast how it got that way...  That's not presently an
   issue here.

   When are people think about this problem, it's possible for them
   to get sidetracked by misjudging the importance of some things
   compared to others, such as the location of a decal, etc..  You
   have to be smart about this, and try to look for the most
   significant elements.  You can quickly get a reasonable idea of
   the effects of various things, to within an order of magnitude,
   and either decide whether they matter, or move on to some other
   factor that matters more.  Don't let yourself get too intimidated.

   Doug Dawson
   dawson@p...

   Just say, Jeff, you're one of the people who originally suggested
   that all this would be a good thing to look into, etc.