Thanks for that link. I like this notice from the USFS about the document:
This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
Below is the text of it (might be a previous version, with transcription errors). First, a highlighted paragraph about what to look for if you're buying an axe handle:
The man who is buying only one handle will usually
find a visual method of judging hickory more convenient
and practical than weighing. A fairly reliable visual
guide to strength is found in the proportion of summer-
wood appearing on the end of the piece. The summerwood
is the solid-looking or less porous portion of each
yearly growth ring. It is quite easy to distinguish
from the springwood portion of the ring, which is full
of pores or small holes. The summerwood has much greater
strength than the springwood, because it contains more
wood substance per unit volume. Wide bands of summer-
wood and relatively narrow bands of springwood, there-
fore, indicate a stronger piece of hickory than bands
of summerwood and springwood of nearly the same width.
The greater the proportion of summerwood in a tool
handle or other piece of hickory, the greater will be
its strength.
FOREST PRODUCTS LABORATORY - U. 5. FOREST SERVICE - MADISON, WISCONSIN
RED HICKORY AS STRONG AS WHITE HICKORY
Usually only a small outer portion of a mature
hickory tree contains white wood; the inner part, or
heartwood, is red. Many people think that this red wood
is not so strong or tough as the white wood. This belief,
however, is discredited by actual strength tests made
at the Forest Products Laboratory upon many specimens
of red and white hickory. The tests show conclusively
that, weight for weight, sound hickory has the same
strength, toughness, and resistance to shock, regardless
of whether it is red, white, or mixed red and white.
The belief that white hickory is superior to red
probably arose from the observation that young, rapid-
growing hickory trees, which are nearly all sapwood,
or white wood, generally have excellent strength properties.
As the tree matures, however, this same sapwood
is transformed into reddish heartwood; and a half-
million tests made at the Forest Products Laboratory
have failed to show any change in the strength of wood
of any species, due to this natural change from sapwood
into heartwood.
A reliable indication of the strength of hickory
is its density. That is to say, of two pieces of the
same size and dryness, the heavier will be found to
have the better strength properties. This fact makes
it possible for large manufacturers or purchasers of
hickory handles or wheel spokes to inspect the pieces
by weight very rapidly and at small expense with auto-
matic machinery.
The man who is buying only one handle will usually
find a visual method of judging hickory more convenient
and practical than weighing. A fairly reliable visual
guide to strength is found in the proportion of summer-
wood appearing on the end of the piece. The summerwood
is the solid-looking or less porous portion of each
yearly growth ring. It is quite easy to distinguish
from the springwood portion of the ring, which is full
of pores or small holes. The summerwood has much greater
strength than the springwood, because it contains more
wood substance per unit volume. Wide bands of summer-
wood and relatively narrow bands of springwood, there-
fore, indicate a stronger piece of hickory than bands
of summerwood and springwood of nearly the same width.
The greater the proportion of summerwood in a tool
handle or other piece of hickory, the greater will be
its strength.
The number of growth rings per inch also affords
some means of grading hickory. Few growth rings per
inch, as shown on the end of a handle, indicate a stronger
and tougher piece than many rings, provided, of course,
that it is straight-grained and free from defects at
important points. Acceptable handles commonly show not
more than 20 rings per inch, although much good hickory
will be found with as many as 40 rings per inch. More
careful inspection, however, by weight, is recommended
for this very slow growth material.
As a further guide in choosing a good tool handle,
it is worthy of note that the best hickory shows an oily
or glossy side-grain surface when smoothly finished;
also, when it is dropped on end on a hard surface, such
as a concrete floor, it emits a clear, ringing tone,
in comparison with the dull sound produced by hickory
of inferior quality.
The adoption by the general public of these methods
of grading hickory, in place of the worthless prejudice
with respect to color, would put an end to the waste-
ful practice of culling red hickory stock. When hickory
was plentiful , this was a matter of seemingly little
importance; but now every means should be taken to
conserve the waning supply of an important wood, for
which no satisfactory substitute has been found.
