LOG SCALING
IN IDAHO
by Ernie Bauer and Russ
Hogan
Scaling
&
Marketing
Private Timber
2006
Scaling
&
Marketing
Private Timber
2006
INTRODUCTION
The material contained in this booklet is intended
for use as an aid to participants attending the Idaho Forest Stewardship
Program, “Scaling & Marketing Private Timber.” It supplements the presentation “Log Scaling
in
Any reader having particular questions regarding
technical aspects of scaling, or provisions of the Idaho Log Scaling Law,
should feel free to contact the office of the Idaho Board of Scaling Practices
for further information. The address and phone number, along with
additional sources of information, are included at the end of this booklet.
WHY WE SCALE
From an historical perspective, log scaling probably
began around two hundred years ago - about the time of the
Industrial Revolution. As sawmills
arrived on the scene, it became necessary to have some means of log
measurement. Log scaling was born.
In its simplest terms, scaling provides the means
for establishing log value. Scaling
gives an objective, quantifiable value for a log. The primary reason for scaling is to provide
a basis for payment. Other reasons for
scaling include:
· prediction of the quantity of end products
· check on the accuracy of cruise volumes
· basis for inventory measure
· basis for tax assessments
· written record of identification
· measure of work accomplished.
Scaling is defined as an arbitrary system of measurement, by means of a log rule, that reflects certain units
of measure in a log. Predominantly,
log scaling in
SCALE vs.
LUMBER YIELD (“OVERRUN”)
The original
Scribner log rule was based on diagramming the number of boards (one-inch
thick, with allowance for slabs, edgings and saw kerf)
that could be recovered from a log of a given diameter and length. The board foot volume was then determined by
totaling the volumes of all the boards.
The original Scribner log rule has seen modifications over the years,
but its “diagram formula” of one-inch boards forms the basis of log scale
volumes used today.
Scribner
decimal “C”
is a modification of the Scribner log rule that uses tens of board feet as its
basic unit of measure. It rounds off
board foot volumes to the nearest 10 board feet and drops the remaining
cipher. For example, if a log scaled 96
board feet by the original Scribner rule, Scribner decimal “C” would round this
to 100 board feet, drop the remaining cipher, and express the volume as “10 boards.” Ten logs (each with a scale of
“10 boards”) would total “100 boards”, which is the scaling expression
for 1,000 board feet.
Throughout the
Board Feet = Width
(in inches) x Thickness (in inches) x
Length (in feet)
12
In many instances, the board foot volume of lumber
that is produced from a log does not equal the board foot volume expressed by
the log scale. When the amount of lumber
actually recovered is more than the amount predicted by the log scale, it is
referred to as overrun; if it is less
than the amount predicted by the log scale, it is referred to as underrun. A formula to calculate the percentage of
overrun (or underrun) is expressed as:
“Overrun” (underrun) in % = (
lumber tally - net log scale
) x 100
( net log scale )
Differences
in scale versus lumber yield are due mainly to the design of the Scribner
decimal “C” log rule versus the type(s) of end product(s) being
manufactured. Scribner decimal “C” is
based on boards that are one-inch thick, actual
size. Lumber production is based on
various nominal size board
measurements. This difference may be illustrated
by comparing the Scribner diagram with a sawing diagram that reflects
production of “two-by-fours” on six-inch diameter logs:
Six-inch diameter logs
1” x 4” actual size boards 2”
x 4” nominal size boards
(1.735” x 3.865” actual size)
Ć1 board foot / lineal foot Ć1.33 board feet / lineal foot
Since lumber products are manufactured in a variety
of sizes, the lumber tally in board feet will seldom be the same as determined
by the log scale. Veneer, chips, and
sawdust are additional products that may be recovered from a log, and require
the use of conversion factors to predict yields. Other factors affecting
“overrun” (or underrun) include log sizes, taper of
the logs, efficiency of milling machinery, and accuracy of the scaler. To account for all the variables would
require a different scale rule for each end-product. In the final analysis, scale is simply a
standard for measuring log volume whose application is independent of lumber
yield.
During the late 1960’s, the
Provisions of the Log Scaling Law govern log scaling
for commercial purposes within the state of
Funding for the Board’s operations comes mainly from
an assessment that is levied on the scale of all forest products harvested
within the state. The assessment is
levied against and paid by the purchaser.
Money received is deposited in a dedicated fund known as the state
scaling account, to be used solely by the Board. Annually, the Board submits a budget for
legislative approval.
Scaling methods used within the state of
[
(b) For the purpose
of payment for logging or hauling logged forest products only, forest products
shall be measured by gross weight, or by gross volume converted to gross
decimal “C” or gross cubic volume.
(c)
(d) Measurement may
be determined by a sampling process.
The law makes provision for the Board to appoint
check scalers.
Check scales help to ensure that scaling standards are maintained. The Board may also perform a requested check scale in response to
disputes involving scaling, and there is a fee for this type of check scale.
Not contained within the Log Scaling Law, but
assigned by the Floating Timber Law are two other responsibilities of the Board
- the disposition of prize logs and the registration of log brands. Prize logs are
logs that have been abandoned for a year or more, after having been placed in
transit. Prize logs are sold by the
Board at public auction. Log brands must
be registered with the Board prior to their use within the state of
Administrative rules describe how a state agency
applies and interprets the law. The Board
has two distinct chapters of administrative rules. Chapter Two addresses general, licensing, and
check scaling rules. Chapter Three
contains measurement rules for scaling in the state of
Chapter Two, rule #100 (Payment For
Logging Or Hauling), provides that gross scale must be determined
according to the Board’s measurement rules.
The rules relating to decimal “C” gross
scale determination are mandatory and specific. These rules address all criteria for diameter
and length measurements. Licensed scalers are required to determine a gross scale volume
accordingly.
Decimal
“C” net scale rules describe the what, and how much, in determining defect volumes for various product
classifications (sawlogs, pulp, and cedar
products). However, these rules relating
to net scale determination also provide that a contractual scaling agreement
may modify how net scale is
determined. As a result, net scale
volume may vary, and most often
does. Written scaling specifications
provide information from a contractual scaling agreement - to the scaler - for determining net scale
volume. In the absence of written
scaling specifications to the contrary, all licensed scalers
are required to determine the net scale volume as described in these rules.
CHECK
SCALING:
Once a scaler is licensed, routine and random check
scales are performed by Board-appointed check scalers. Check scaling is performed to verify scaler
proficiency, and confirm that the scale determination is made in accordance
with the Board’s rules.
A valid check
scale requires checking a minimum of 50 pieces (logs) with a volume of at
least 10,000 board feet (BF). Most of
the time, however, check scales will involve 100 or
more logs with volumes around 12,000 BF or more. When possible, check scaling is done without
the scaler’s knowledge. Valid check scales also require that the logs
being checked are in the same position as presented to the scaler.
Check scale comparisons are tabulated and listed in
a Check Scale Report. This report is
distributed to persons directly affected,
in accordance with the law and rules of the Board.
A scaler must be within allowable limits of
variation in four areas - gross scale, net scale,
species identification, product classification – for the check scale to be
considered acceptable.
A requested
check scale may be performed upon request of any individual, company, or
corporation. The request must be in
writing, made by a party directly affected, and involve disputes on scaling. The fee charged for a requested check scale
is $200 for each day, or part of a day, that the check scaler is scaling the
logs. The fee is payable by the person
requesting the check scale, or by the party in error when check scale results
are outside allowable limits of variation.
The check scale report is distributed to all persons directly affected,
as defined in the Board’s rules.
Since net scale is not mandatory, the scale
sometimes does vary among mills. The
same load of logs may have greater (or lesser) scale at one mill versus
another. This apparent anomaly is often
due to variations in the contract scaling
specifications. The following table
compares some of the items that may vary by contractual agreement with the
Board’s rules - that would otherwise apply in the absence of an agreement.
|
Some Common Sources of Net Scale Variation Among Mills |
|
|
Contract Scaling Specifications |
Current Board of Scaling Practices Standards
(Default Scaling Specifications) |
|
Minimum Trim Allowances |
None |
|
Scaling in 1-foot or 2-foot Multiples |
Scaling in 1-foot Multiples |
|
Log Lengths Acceptable or Special Lengths |
All Log Lengths from Eight Feet and Longer |
|
Minimum Top Diameter |
6-inch Scribner Class |
|
Sawlog, Pulp, Cedar Products Scaling |
Sawlog Scaling Only |
|
Combination Logs are Scaled |
No Combination Logs are Scaled |
|
Special Defect Deduction Provisions |
According to USFS Scaling Handbook and as Stated in the Board’s Chapter 3 Rules |
|
Volume Tables |
Board’s Chapter 3 Rules |
|
Multi-segment Butt-log Taper |
Board’s Chapter 3 Rules - Generally USFS Taper Tables |
|
Minimum Merchantability Percentages |
Sawlog - 33 1/3 % Pulp - 50 % Cedar Products - 10 % |
The majority of check scale results show licensed scalers within allowable limits of variation.
|
Category |
Allowable Variation |
||
|
|
For logs in round form |
+/- 2.0 percent |
|
|
For logs in fractional or slab form |
+/- 5.0 percent |
||
|
Net Volume |
Sawlogs |
Check scale percent of defect on logs checked |
|
|
Up to 10 |
+/- 2.0 percent |
||
|
10.1 to 15 |
+/- 3.0 percent |
||
|
15.1 to 20 |
+/- 0.2 percent for each percent of defect |
||
|
Over 20 |
+/- 5.0 percent |
||
|
Pulp Logs |
+/- 5.0 percent |
||
|
Cedar Product Logs |
+/- 8.0 percent |
||
|
Species Identification Errors |
3.0 percent |
||
|
Product Classification Errors |
3.0 percent |
||
ADDITIONAL
SOURCES OF INFORMATION
National
Forest Log Scaling Handbook
This contains a wealth of
information regarding technical applications of scaling.
VO-ED No. 38, A Manual of Instruction for Log Scaling and the Measurement
of Timber Products
For a number of years, this
was recognized as the premier training manual for new scalers.
The text
of
Rules of the
The administrative
rules of the Idaho State Board of Scaling Practices.
Any of the references listed above may be viewed at
the office of the Idaho State Board of Scaling Practices during normal business
hours (please phone ahead for an appointment).
Some libraries or consulting foresters may also have copies.
Have a
computer with access to the Internet? If so, you
may do online viewing at these addresses:
http://www.ibsp.idaho.gov Official website for the Idaho Board of Scaling Practices. This contains general information on
http://www.legislature.idaho.gov
Phone: 208-769-1445
Fax: 208-769-1524
E mail: