MEETING MILL SPECIFICATIONS

All mills expect good workmanship in log quality. This is an important issue because poor bucking, limbing, or excessive defect in log manufacturing practices results in reduced product recovery. To maximize productivity, mills also require that logs be manufactured according to their specifications. Mill specifications ultimately determine how much will be paid for any given log.

Depending on the type(s) of end-products a mill may produce, some species, sizes, lengths, or defects in a log may be unacceptable. But even among mills producing the same type(s) of end-products, there are often differences in what constitutes a properly manufactured log. Before a logging job begins, anyone involved in the manufacture of logs should become familiar with purchaser mill specifications.

Type of Mill Product	General Log Type Preferences
	Species Used	Scaling Lengths	Scaling Diameters
Boards	WP, PP, LP, S, C	2-foot multiples	6-inch plus
Dimension & Boards	All species	2-foot multiples	6-inch plus
Studs	LP, DF, L, GF, H	8-foot multiples	5-inch/6-inch plus
Plywood	DF, L, GF, H	8.5-foot multiples	9-10” to 20-22”
Specialty Veneer	WP, PP, C	17, 26, 34	Small WP, Large PP & C
Pulp	All species except C	1-foot multiples	3-inch plus
Utility Pole	LP, C	35+ (5-foot multiples)	12-14” dbh trees
Cedar Products	C	Various	15-inch plus

QUALITY CONTROL: PREFERRED LOG LENGTHS AND PROPER TRIM

One of the more common mill specifications contained within a timber purchase agreement addresses preferred log lengths and proper trim. The log lengths preferred by a particular mill will depend on the type of product(s) that they produce. The proper trim allowance on a log ensures both that effective utilization of the tree has been made, and that the mill can produce a finished product of a given length.

In general, most mills want and accept logs manufactured in 2-foot multiples – with proper trim allowance. This allows a logger the ability to vary the log lengths and realize maximum utilization on harvested trees. Preferred log lengths allow a mill to more efficiently produce their finished product. The price paid for purchased logs will be predicated to some degree on the number of “preferred length” logs. Never assume that a log length which was acceptable at one mill will necessarily be acceptable at a different mill. While most mills accept a variety of similar log lengths, there is no universal standard – always refer to mill specifications. One common example of this occurs with 8-foot (plus trim) log lengths – at some mills, a log of this length is unacceptable and will be culled for net scale.

Scaling Length Determination
Typical Manufactured Log Lengths (with full trim allowance ... these often may vary by plus or minus 2”)	Scaling Length	Log Segmenting
		Butt Segment	Top Segment
* 8’ 6”	8’	8’
10’ 6””	10’	10’
12’ 6”	12’	12’
14’ 6”	14’	14’
16’ 6”	16’	16’
* 17’ 6”	17’	17’
18’ 6”	18’	18’
20’ 6”	20’	20’
* 21’ 0”	21’	11’	10’
23’ 0”	22’	12’	10’
25’ 0”	24’	12’	12’
27’ 0”	26’	14’	12’
29’ 0”	28’	14’	14’
31’ 0”	30’	16’	14’
33’ 0”	32’	16’	16’
35’ 0”	34’	18’	16’
37’ 0”	36’	18’	18’
39’ 0”	38’	20’	18’
41’ 0”	40’	20’	20’
* 8’ 6” and 17’ 6” and 21’ 0” log lengths should be cut only when requested by the mill buying the timber.	When segmenting scaling lengths in excess of twenty feet (20’), the longer segment always goes on the butt (or large) end of the log.

Occasionally logs are bucked without proper trim allowance. There are several reasons for this happening, all of which can and should be quickly corrected. The overall length of a log determines the gross scaling length, and incorrect trim allowance may result in a defect deduction to arrive at the net scaling length.

Proper trim allowance is neither too much nor too little. A log having too much trim allowance does not effectively utilize all of the tree. Overtrim may result in additional gross scale volume, but there is no benefit realized in finished product length. Quite often, a scaling deduction is made to reflect the finished product length that will be realized. A log having too little trim allowance is a costly mistake. Undertrim logs result in a finished product length that is shorter than what was intended. Depending on log size, length, and mill specifications, a scaling deduction for this type of “avoidable defect” can be substantial. A mismanufactured log length can easily result in a log being culled that would otherwise be an acceptable log.

* Examples of Some Acceptable and Mismanufactured Log Lengths
Manufactured Log Length	“Short” Log Length	“Long” Log Length	Gross Scaling Length	Net Scaling Length
8’ 4”			8’	8’
8’ 3”	Yes		8’	CULL
16’ 4” through 16’ 8”			16’	16’
16’ 3”	Yes		16’	14’
16’ 9”		Yes	17’	16’
32’ 10” through 33’ 2”			32’	32’
32’ 9”	Yes		32’	30’
33’ 3”		Yes	33’	32’
* Assumes contract scaling specifications requiring net scale determination in two-foot multiples, with minimum trim allowance of 4” on single-segment logs and 10” on double-segment logs.

GETTING THE MOST SCALE FROM YOUR LOGS

Increasing the scale of your logs involves understanding all the aspects involved in converting a standing tree to the finished products. Knowledge of how scale is determined, what reduces scale, and what does the mill need, all come into play in deciding a log manufacturing strategy. Avoiding the mistakes in log manufacturing is one of the best ways to realize greater scale.

Maximizing scale begins with felling of the tree. Errors to avoid include high stumps, stump shots, stump pull, and falling breaks. The higher the stump, the smaller the scaling diameter will be as you work your way up the tree making log lengths. Stump shots are undesirable log quality defects. Stump pull and falling breaks may reduce scale.

Bucking a felled tree into log lengths results in the real measure of log value. Logs are scaled as presented, and its length will determine many of the rules applied in scaling that log. Pitfalls to avoid include non-preferred lengths, short (or long) trim, small tops, bucking breaks, bias-cuts, protruding limbs, and excessive defect left in logs.

Being able to identify and understand how certain defects will affect the scale of a log is a great help in deciding how to buck a log. Various types of natural defects occur in any stand of trees. In manufacturing logs to get the most scale, the strategy is to reduce or eliminate the defect and, at the same time, make the best use of the resource available. While a logger may have little control over natural defects, most man-made defects can be reduced or eliminated.

Two special types of defects should always receive a log manufacturer’s scrutiny. Most mills will not purchase logs that have “char” defect, and always, always, totally eliminate any “foreign object” defect (most commonly, iron) from a manufactured log.

Examples of Some Scaling Defects & Causes
Natural Defects		Man-made Defects
Disease	Trunk, heart, butt, & sap rots	Falling	Stump pull, barber-chair, shattered logs
Insects	Bark beetles, carpenter ants, borers	Skidding	Track gouges, limbing gouges, breakage
Stress	Heart checks, shake rings, massed pitch	Bucking	Improper lengths, slabbed ends, splits
Perils	Lightning scars, fire, porcupines	Loading / unloading	Broken logs, gouges, slabbed logs

Ways to reduce or eliminate natural defects depend on the type, and severity, of the defect identified. Some defects must be tolerated because they cannot be reduced. Pitch seams, small to medium size frost cracks, and minor cat-faces should not be bucked out.

Other kinds of defects can be reduced by varying the length of a log. An example would be making shorter lengths to reduce excessive sweep. Bucking a log completely free of sweep results in poor utilization of the forest product. Properly bucked, the defect is minimized.

[On the log shown below, first make a 10-foot butt log and then make the 32-foot preferred-length log]

Defects affecting a considerable portion of the scaling cylinder should be eliminated. Examples would include severe butt rots or heart rots. In bucking for this type of defect it is important to remember not to buck off too much or too little. Generally, when the length affected by defects would result in the scale being less than one-third sound, wood should be eliminated.

[On the log shown below, buck off the first 4 feet and then make the 16-foot preferred-length log]

OTHER LOG MEASUREMENT METHODS

(wt., cubic, etc.)

Throughout the state of Idaho, the most common measurement method used for buying and selling logs is the Coconino Scribner decimal “C” log rule. A few other measurement methods are categorized and described below.

Sample Weight Scale	A statistical sampling procedure generally applied to larger volume sales.
Approximate Weights of Wood (Pounds) Weight	Although an objective method of measurement, a number of variations exist, such as seasonal changes in weight and fluctuations in pounds/MBF based on differing diameter classes. Some comparisons (reprinted, in part, from VO.ED. # 38, 1974 edition) are listed in the table below.
Cubic Scale	A scaling system based on the cubic foot, 12" x 12" x 12". It offers many advantages over board foot diagram rules. Disadvantages include a reluctance to change measurement units and the costs of implementation.
Truckload Volume by Cordwood Measurement	Measures height, width, and length of a load of logs and converts the volume to board feet. It is being used at some locations for pulp logs.
Lump-Sum	Sales based on cruise volume data.
Westside Scribner Scale	Based on a 40-foot scaling segment with diameters rounded down to the full inch. Has diameter & length-cut deductions only.
Pole Measure	Based on length, diameter, and pole grading standards.