On Wed, 09 Feb 2005 19:05:42 -0500, Tom Watson vaguely proposed a theory ......and in reply I say!:
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Yes. The endgrain is far weaker for screw holding, both for pullout and for movement sideways. That holds even more so if the screw is pulling along the wood end, rather than across it. This gets difficult, as I reckon the screw will start _loosening_ more easily along the end, but will tear the wood to pieces across ways more easily.
If the end is clamped between other wood (in a dado for instance) this can change a lot.