paul womack wrote:
> 
> r = 2.5"
> 
> So that's the radius Stanley ground a #40 1/2 scrub blade to.
> Wether it's the best radius is another question

Good question.  What are the factors that would determine the optimal radius for
a scrub blade?  Off the top of my head I get:

How strong is the person using the plane?
What type of wood is it being used on?
How wide is the blade (a given for each plane but which plane will you use?)

It seems that the tradeoff (assuming that you are trying to remove as much
material as possible for the least expenditure of energy) is between shortening
the "shear" line of the shaving (where the fibers need to be seperated from one
another) and the ability of the chip to bend as it passes through the mouth of
the plane.  Reducing the radius toward the minimum (1/2 of the width of the
blade) allows you to remove a greater volume of material for a given shear line
(right?) but leaves you with a thicker/stiffer chip.

Of course reducing the radius may also limit the utility of the blade as it
reduces the amount of material that you can remove per pass if you are not using
the maximum depth that you can handle.

-Ken