T
he life of a table is not easy. Legs get kicked; the table
gets pushed and pulled across uneven floors, leaned
against, and sometimes even sat upon. To make matters
worse, the very nature of wood adds to the stress. As the tabletop
shrinks and swells with seasonal changes in humidity, the move-
ment works against the integrity of the table’s structure. All that
stress is felt in the leg-to-apron joint (above), which holds a table
together and gives it rigidity. When the leg-to-apron joint fails,
the table falls apart.
Build sturdier tables by beefing up
the basic mortise and tenon
B Y G A R R E T T H A C KStrong Joints
Photo, this page: Michael PekovichBUILDING TABLES ]
Leg-to-apron joints must withstand three different kinds of
stresses: shear, bending, and twisting. Shear stress is caused by
a vertical load directly above a joint, such as when someone sits
on the corner of a table. Leaning heavily on the top of a table
midpoint above the apron causes the joints to undergo a bending
stress that tries to lever them apart. Shoving the table sideways
or bumping against a leg gives the joints a mixture of twisting
forces. Also, as a tabletop that is fastened too tightly to the apron
expands or shrinks, it can try to twist the joints.34 F I N E W O O D W O R K I N G