Something new in hardwood log grades


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Something new in hardwood log grades
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Mixed Material
Benson, A. O
Forest Products Laboratory (U.S.)
University of Wisconsin
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory ( Madison, Wis )
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aleph - 29328385
oclc - 294861556
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Full Text


January 1941


Madison, Wisconsin
In Cooperation with the University of Wisconsin

Digitized by the Internet Archive
in 2013


13 A. 0. 3b:30 c, ood Fechnologist

','ith the reduction of large holdings of virgin stands of timber r ad in
turn the increasing necessity for lumber manufacturers to purchase. their Mos
from scattered small holdings and farm woodlots, the matter of log grain is.
assure a role of greater importance. Good logs are getting scarcer. I Is
have been faced with the necessity of using a continually increasing upropor-
tion of poor logs. ;vhen logs are bought by the thousand feet instead- of p -
ing cut from the company's own lands there is a greater endeavor to make
every dollar buy a dollar's worth of timber. How is the buyer to ascertain
whether he is gettin,7 his money's worth? On the other hand, there is r:he
seller's interest to consider. How is he to know that he is getting what his
logs are worth? Obviously, the answer is fhe same '- the one that would be
given for similar questions concerning tran sactions in lu:er, cotton, wheat,
and a host of other products, namely, through a grading system. T.-re is a
general recognition of this fact which is mianifested by the increasing' de-
mand for some system that cill enable group segregation of logs of like

Some lumbermen view lo-g grading as simply another chore to be added te
their already crowded routine. Still others view it as a necessity in a busi-
ness that is becoming increasingly competitive. Upward trends of costs an,
greater demands in refinement of product without commensurate trends in
prices of product are a combination that is resulting in survival only of the
fittest. And the fittest are those who know their business don to thie
minutest details from raw material in the form. of logs on through to the
finished product.

Log grading is not a new thought. Log quality classification of some
sort has figured in log transactions for many years, but in hardwoods it has
never made notable proc-ress. Log grade specifications arc little different.
now from those set up years ago. Although there has been some attempt on the
part of re,-ional organizations to secure adoption and general usae of stand-
ard grade specifications little has come of such efforts, for the practice
persists of each log buyer accepting logs based on his individual si ecfica-
tions. Such specifications are generally unwritten ones, and th'e buy-r is the
sole interpreter of the quality classification. Th practice is not without
its advantages, for th, user knows best the classes of lorgs that will meet his
needs, but on the other hand there is no common meeting -rTound for buyer and
seller so that lack cf understanding is general and the seller is often left
with a feeling that he might have done better if he had knovn more definitely
what was in the buyer's mind.

--Published in the Journal of Forestry, January 1941.

The Old Conception -- Log Grades Based on Defects

Attempts to grade logs have employed the principle of defects as a
basis for quality classes, for it would appear obvious that logs with visible
defects would be of poorer quality than those that were surface clear. The
problem, therefore, has resolved itself into a matter of establishing degrees
of p-.rmissible defect for certain quality classes; for instance, a Nc. 1
grade would admit few or no defects, a No. 2 grade would admit more defects,
and a J4o. 3 grade still more defects. Such a system would be certain to re-
sult in a rough quality stratification of lumber, but invariably the experi-
once has been that there has been too much overlapping imn grades; that
is, logs graded as No. 1 would often cut out a No. 2 grade and vice versa.

The fallacy in the defect system of grading logs is that it is incon-
sistent with the way hardwood lumber is graded. With limited exception, the
spec ifications for the hardwood lumber grades make no reference to defects.
Thy take their cue from hardwood lumber and the way it is used. About '
percent of hardwood lumber is cut up before it is put in place in the final
product -- chairs, tables, caskets, toys, and the like. For most uses the
cuttingts must be clear or at least clear on one side, on edges, and on ends.
Consequently, the hardwood lumber -rades are based on0 percentage of clear-
face cuttings of specified minimum sizes. Does it not follow, then, that log
grades should be based on some principle that recognizes the value of large
def.ct-fre, areas instead of placing emphasis on number and size of defects
and disregarding their location?

Extreme difficulty is encountered in endeavoring to apply defect
specifications. In order to simplify specifications to a reasonable degree it
is necessary to establishh a standard defect and translate the damaging- effect
of miscellaneous defects into terms of such standard. For instance, if a
standard defect is stated to be a J-inch knot, then cat face, bird pock aroas,
opcratine defects, and the many other common defects must b, considered from
th,' standpoint of their effect onr quality of lumber in comparison with the
lumber degrading effect of a 5-inch knot. Except for the man who has spent
a lifetime kenly obs-rving lo-s boil,- cut up and has formed definite ideas
with respect to the damage caused by various types and sizes of defects, the
comrarativc. or equivalentt principle is merely guesswork of the most hopeless
kind. Vry few men who are called upon to grade; logs havo had the opportunity
to make adequate study of the,. vay logs open up. It is necessary, therefore,
to make the log,- grading system just as simple as possible consistent with
reasonably accurate results.

In this ,onnection it is inter.,stirng to recall that in the process of
evolution of hardwood lumber grad s th gIrade of Firsts and Sconrids, once
determined on the' basis of' defects, was changed to a cutting grade. Students
f hardwood lunb r grades:; saw the need for gre after simplicity and accuracy.
.en ynar of xp r cnc with the changryd grade has proved the wisdom of con-
c:ntrat ni- attention on cu ttinrs inst ad -f on defects.

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Th; NIew Conception. -- Log 'rades Based on Dofect,-Free Ar ,a:.

Judging defect-free areas imposes no difficulties. Bar: surface ,-
focts ar-; subordinated and th, problem becomes on( of d t'rminin.- thi :":i f
the clear cutting area between defects. Thus, the main principal ; o, ;ralIn,-
hardwood lumber is used as the starting point for log grades. '.hen i cm, t
application of this idea it was found advantageous to visualize the surfc
of the logs as divided into quadrants with corresponding' division of the lar
surface into four sides or faces. Each faco, then, could obe 'urveed
independent of th.. others, and except for the curvature it would appear much
as a piece of lumber.

Going again to the lumber grades, it will be found Jhat th, up- r 'rads
specify a certain high prrcentag' of' the surface must yield clear" fa, cu-
tings of a certain size or larger. iere again, ar-, reojuir-.ments that can be
applied in principle when survying the faces of th, log. haturilly, all log
grading systems strive to get a maximum yield of high-,rade lur -r in th
highest log grade. By following thK, sp, cifications for Firsts and Seconds
hardwood lumber, the top grade, as closely as possible and incorporating th m
in the iNo. 1 log grade specifications it should bu possible to group in this
grade the logs that would yield a portion of their volume in Firsts and
Seconds lumber. Similarly, the specifications for the lorir hardwood lumber
grades could be followed for the low jr log grades. _y adopting this id-.a
the Forest Products Laboratory has demonstrated by actual mill test that it
is a practical procedure It has also beIen found that the tendency experi-
enced in defect log grades for misallocation of logs is greatly reduced.

In applying the log grade specifications it has beu:' dLtrincd tlat
requirements for the log are sufficiently realized if thr. out of th four
log faces make the grade. Time is thus saved and thlie grain proce dure is

Aside from th- sp cifications built around cuttingF sizes and per-
centages of yi,.ld, other grade controlling factors are introduced. ['.
influence of size of log on value is recognized so that steps in sizes ar;.
set up, thU. higher the grade the gr ater the restriction on sr,all,..r los.

Interior log defect as indicated by defective end surfices is ,'ikn
into account. l'aximum scale deductions on account of interior defect ar'
spencified independent of the quality as indic'atcd b' I th bark surface, .
Crook and swmveep are restricted.

Standard Specifications te Apply to All S,'m. and All R'',-ins

Speci es vary on front. the othi. r wi thin r io: 7n a '
species may have character stiics in one region that arx. lucking in anoth r
region. n NvurthKless, thu :work done thus far inicati s th,'at stadard
grade sp cifications may b-, madc to apply regardl]ss of" sn; cr .s r reion
much the same as standard hardwood lumber -rading rul';s ar applied a

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present. It will b7 necessary to provide modifications to take care of
th, peculiarities of certain species, but such details do not look too

To date more than 7,000 logs of about 20C different species of northern
hardwoods have been g-iven detailed study by the Forest Products Laboratory,
and the representation for this region is considered adequate. Field work
wil] be extended to other regions.

Specifications Based on Intensive Studies

Field studies include diagrammning log surfaces and getting lumber grade
tallies for the individual lops. Subsequently the log diag-rams can be used
for trial of any log grade specification that might be up for consideration.
The diagrams are virtually pictures of the log surfaces. 'All features that
might affect the quality or quantity of yield are precisely positioned and
described. Tre matching ef log product uith tno ir.fermation obtained from
the diagram reveals the ini'luerce of type and extent of defect on quality and
quantity of yield.

Previous attempts to formulate log grades have not been based on de-
tailed studies iof this or any other kind. They have in the main resulted
from some individual or group of individuals wrIting specifications based on
the best judgment and experience that could be brought to bear. Under such
methods fa-lty judgment would not be detected until the -giading system was
actually in use. Revision of specifications when.-undertak.e At all has been
a slew and uncertain process. The present approach seeks to anticipate the
shortcomings of th3 specifications by what amounts to actual trial by means
of the log diagrams.

K, new grading method being developed is not wholly something on
paper, for it h'1 been given trial by three log purchasing -gencics and no
impract icl feno ur- s h-iAv cme to light. It ha also n esod ec1perimcntally
to grade logT hi t i itidin treo, a procedure that 1i o) come increasingly
important in maL.inA tbr appraisals. At the pr se, t 7a, t hcwevor, no
special resear '-itt ntion by the horost Products Laboratory is being given
to applic'ationi of the lo,- grades to trees. To formulate a log grading system
i a mattr sufficiently complicated without still further confusing it with
tre groadifa however urgent may b the demand for the tree phase of the

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