Slightly curved grain is OK (by curved I mean curved in the cross section). Lengthwise the grain should be running straight.
What is most important, that the grain should not run diagonally out of the side of the handle.
Vertical or near vertical grain is more important in long handles than in short ones.
While there are several “rules” regarding the optimal type of handle wood, they are not absolute ones.
As with many things in real life, the criteria regarding acceptable axe handle wood are more complex than to squeeze into a couple of rules.
Still, there are some traits which are statistically associated with higher frequency of failure, so they are
best to avoid - if possible.
Several years ago I have posted the following quotes in two similar threads on another forum:
http://www.fpl.fs.fed.us/documnts/us...d/241hicko.pdf
"Over the years a prejudice has developed against the heartwood of hickory. Red hickory (heartwood) is often placed in a lower grade than white hickory (sapwood) simply because of its color. Tests by the Forest Products Laboratory have shown conclusively that red, white, and mixed red-and-white hickory have the same strength characteristics, regardless of color. The negative attitude toward red hickory developed during the days of virgin hickory stands. Under virgin-stand conditions the heartwood was often less dense and not as strong as the sapwood. In the second-growth stands of today this density difference does not exist, and specifications and utilization practices should be adjusted to take this fact into account.”
http://abcworld.net/Wood
"Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in the forest, and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and spokes. Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that:
"The work or shock-resisting ability is greatest in wide-ringed wood that has from 5 to 14 rings per inch (rings 1.8-5 mm thick), is fairly constant from 14 to 38 rings per inch (rings 0.7-1.8 mm thick), and decreases rapidly from 38 to 47 rings per inch (rings 0.5-0.7 mm thick). The strength at maximum load is not so great with the most rapid-growing wood; it is maximum with from 14 to 20 rings per inch (rings 1.3-1.8 mm thick), and again becomes less as the wood becomes more closely ringed. The natural deduction is that wood of first-class mechanical value shows from 5 to 20 rings per inch (rings 1.3-5 mm thick) and that slower growth yields poorer stock. Thus the inspector or buyer of hickory should discriminate against timber that has more than 20 rings per inch (rings less than 1.3 mm thick). Exceptions exist, however, in the case of normal growth upon dry situations, in which the slow-growing material may be strong and tough." "
According to
http://www.fpl.fs.fed.us/documnts/usda/tb342.pdf
"Too much reliance should not be put on ring width in judging the
quality of wood, since for any ring width large variations in strength
may occur, because different growth conditions may produce similar
rates of growth but different proportions of the various types of
tissues found in wood."
and:
"No generalization on the relative toughness of sapwood and of
heartwood or on the occurrence of brash wood in either can be made.
In old, slowly growing trees the sapwood is frequently low in toughness
and may even be brash, on account of the large percentage of
spring wood or other porous tissue that it contains.”
Best,
littleknife
