Posted tagged ‘wood movement’

The Arrogance of Experience

February 27, 2021

    There is no substitute for experience.  Your skills become more practiced.  Your knowledge base broadens (and, hopefully, deepens).  You develop shortcuts that help you expedite the completion of routine tasks.  You learn that there are certain rules that can be “bent” without injuring the outcome of a project.  And, this is where the arrogance comes in.  If you bend the rules enough times, without injury or negative effect, you begin to forget their importance.  This phenomenon can be very bad indeed, as when not using a push stick while ripping stock on a table saw.  “Serial rule breaking” can call into question the abilities and wisdom of even the most seasoned craftsman. 

    All competent woodworkers know that they must plan for wood movement.  This is a rule, a really BIG RULE!  Good designs accommodate the material’s natural tendency to move with changes in humidity.  Of course, the first rule is to work with material that is at equilibrium.  That is to say that the moisture content of the material remains relatively constant.  (Best test for determining equilibrium is to weigh a sample over the course of a week or so to determine changes in moisture content.  Several days without significant decrease in weight indicate a state of equilibrium.)  In this part of the world, 9% is considered to be indicative of material at equilibrium.  Experience tells us that most domestic species can be worked in the shop without fear of significant movement of deformation at moisture levels between 8-10%.

    Construction grade material is typically worked at much higher moisture content.  Many of us have had the experience of hitting a piece of framing stock with a hammer and then witnessing the resultant “dimple” fill with water, as if “by magic”.  The probability here is that this is material at 20% (or higher) moisture content.  Probably okay for framing a garage, not so good for “bench work”.  So here is my story…

    I’ve been “re-doing the shop” (for about the tenth time in seventy-five years).  I built a large layout table to replace several work benches that now reside in my friend, Chad Stanton’s shop.  I used southern yellow pine for the table top.  It’s a great material for this type of use, tough and inexpensive.  As it’s winter, I concluded that several days of acclimation in the shop would be adequate.  Indeed, Chad and I put a 32″ x 120″ top together with just the slightest hint of a cup.  And, that was overcome with substantial lag bolts, sliding on fender washers.  Voila!  Layout table in place and working as planned.  Sixty-plus years of experience pays off again!

    So, I decide to build several little storage boxes for things like Stanley 45’s, et cetera.  I’ve got some cut-off stock from the table top.  Might as well use it.  It doesn’t have to be anything fancy.  After all, these are just going to be little sliding top boxes.  They’re just for keeping stuff out of the dust.  I split a couple of pieces of 2×12, plane them to about 5/8″ and proceed to build a little dovetailed, five sided box.  I glue it up and slip the top into place.  Turn off the heat in the shop.  Take the box into the kitchen to allow the glue to dry overnight….

    It should come as no great surprise, when in the morning it required a substantial amount of effort to remove the top from the box.  I had BENT THE RULES!  The arrogance of my experience had taken over my thought process.  I disregarded the rule of equilibrium, to my shame!  Mea culpa…

By the way, Semper Optimum translates to “Always your best”.  I stand humbled.  Mea maxima culpa.  There are reasons for rules (even for old guys).  It’s good to be reminded every now and again…                  (And, always use a push stick!)

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