> On Sep 6, 2021, at 11:22 AM, Dan Beck  wrote:
> 
> I see what you’re saying - thanks for the clarification. I followed the
directions provided by Mike Seimsen in his video “Naked Woodworker”. In this
video (released by Lost Art Press) he very clearly instructs screwing the top
planks to the aprons and cross bearers and using carriage bolts to attach the
legs to the aprons.
> 
> I’m hoping that this won’t be an issue. I stored the lumber in my shop for a
couple of weeks before building and tested them with a moisture meter before
attaching them. The levels were in range, so fingers crossed that wood won’t
move much.
> 

I just happened to finish reading Shaker Inspiration by Christian Becksvoort,
and he goes into pretty good detail on wood movement, and includes a table for
Dimensional Change Coefficients for Shrinking or Swelling Within Moisture
Content Limits of 6 to 14 Percent.  Basically, he explains how to calculate how
much a piece of wood can grow or shrink based upon its current moisture content
and its possible extremes of moisture content. For an 11” wide board of Loblolly
Pine,  moisture change from 6% to 14% will bring a corresponding change in size
of  slightly    over 1/8” for quarter sawn wood and slightly under 1/4” for flat
sawn wood.  (Rift sawn will be somewhere in between.)  That is enough to do some
damage if the bench (or other object) actually sees that kind of moisture change
and isn’t built to allow for it.

Movement = board width x percentage change in moisture content as a whole number
x Dimensional Change Coefficient

Radial (quartersawn): 11” x 8 x 0.00165 = 0.1452” or slightly over 1/8”

Tangental (flat sawn)” 11” x 8 x 0.00259 = 0.228” or slightly under 1/4”

This of course is the most extreme case.  Also, using deck screws for the
attachment also provides for some allowance for wood movement.

Traditional wood screws have a shaft that is the same size as the major diameter
of the threads.  You drill a clearance hole to match in the top piece of wood,
and a pilot hole in the bottom piece of wood.  Deck screws have shafts that
match the minor diameter of the threads.  The threads are actually 1/16” or so
wider than the smooth shank.  If you drill clearance holes in the top piece of
wood that are wide enough for the threads to pass, they will be oversized for
the shank, and will allow for some wood movement.  Some longer carriage bolts
also have smooth shanks that are smaller than the major diameter of the threads.

Bottom line is that it is probably OK if you do not expect huge swings in
humidity between summer and winter, but if you do get that type of humidity
change, you should make some adjustments to allow the wood to move more.

David Sobel
who built a workbench in an unconditioned Florida garage in the middle of
summer, and then put air conditioning in the garage.  When the bench top shrunk
by roughly 3/32”, I was glad I had allowed for wood movement in the aprons and
the attachment of the top.