Hand Tools Archive

Tree to tree differences

Bill Tindall, E.Tn.
K&K showed that dulling is proportional to wood density. Makes sense. More solid stuff in the way of the blade tip, and hence less air, more stuff to rub and dull.

I sawed a walnut a few years ago whose wood is as light and soft as pine. Growth rings are not unusual. It is just light. I have some white oak that is as mellow as poplar. As a demonstration I was able to easily drive a #4 finish nail into it. And I have white oak so dense that it bent hardened flooring nails. I'll bet there is a large difference in how these boards dull.

Details of growth will change the ratio of early wood to late wood. Given the cell structure is different the planing could be. And K&K saw a large difference in dulling affected by grain slope. Grain that promoted tear-out dulled less because the wood was splitting ahead of the blade tip and there was less rubbing. Grain the opposite direction would spring against the blade and cause more friction.

However, I remain skeptical about the difference in dulling of heartwood vs sapwood. I found nothing in the literature to suggest a difference in density for the same tree. The garbage the tree deposits is composed of organic chemicals that are not abrasive, unless corrosive abrasion is a factor, which seems unlikely for a stainless steel. But we are faced with a substantial difference between two boards that has some explanation. A curiosity, but not one that affects David's conclusions.

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