in humid weather. Our emphasis on
high yield can also discourage end
trimming from being a bit excessive,
just in case. In fact, sometimes computer scanners will automatically take
and inch off the end of the lumber, but
sometimes the check is indeed longer.
Now, what happens in the dry oven,
is that there is a small amount of drying and shrinkage, but the strength of
the wood right at the end where there
is a closed end check is zero, so the
stress opens this preexisting check. In
my experience when analyzing rough
mills, this is reason for end checks in
wood 99 percent of the time.
Note that this is the same scenario
that happens with a face check. During
drying, some small, barely detectable
checks developed on the face. When
planing these small checks, sometimes
they are not fully removed. So we have
a tightly closed opening on the face.
The dry oven dries the wood, the wood
Weak glue joint
shrinks and with zero strength in the
vicinity of the check, we see an open
Another reason for an end check opening, especially in the wintertime, is that
the glue line is weak. A properly made
joint will be 1-1/2 times stronger than
wood, but if the ends are not properly
glued, then the strength of the joint is
much lower. A little drying in the oven
means the ends dry and shrink a little
bit, creating stress that exceeds the
strength of the weak end joint.
The #1 reason for poor end joints
is that after the individual staves for a
glued panel were prepared, the ends
shrank a small amount so when we
made the joint, there was a small gap
(maybe only 1/100 inch) at the ends;
most adhesives do not bridge this size
gap and maintain their strength.
QAs we look at improve- ments in our cabinet opera- tion, we seem to believe
that improvements in yield
are much more valuable than improve-
ments in the cost of labor or machin-
ery. Does this make sense to you?
AYes, I do agree with you. Improvements in yield are often three times more important (financially)
than savings in labor or machine cost.
Stated another way, the wood cost of
manufacturing the final product is
often around 75 percent of the total
production cost. So, this means improvements in yield will have a bigger
impact than labor savings. (Of course,
safety is always the #1 item, so yield is
However, before becoming too
concerned about yield, we must also
consider the cost of the raw material.
As an example, when we buy No. 1
common oak, we might get 60 percent
yield. If we looked at No. 2 Common
grade, the yield might drop to 50
percent, but because No. 2 costs half
Improvements in yield are often three times more
important (financially) than savings in labor or