The Dowel Joint
Why round tenons fall out of round holes, and the elastomer compromise
Synopsis: If good dowel joints aren’t the oldest joints ever made, loose ones must be, writes R. Bruce Hoadley. He studied dowel joints to find out why they fail and to discover the recipe for a joint that wood not fail. He found that conflicting dimensional behavior of the mortise and the tenon in response to humidity change can cause self-induced loosening. In this detailed article, he explains the self-destructive effect of moisture variation on the traditional dowel joint and suggests remedies and lines for further exploration. He establishes five checkpoints for making joints with the best chance of survival: proportions, original moisture content, mortise surface quality, grain/growth-ring orientation, and finishes. He covers adhesives and plenty of drawings illustrate various points. Side information talks about another solution from John D. Alexander, Jr., using green wood.
From Fine Woodworking #21
Dowel joints must surely be among the oldest methods of…