United States 

Department of 

Agriculture Yield Losses

Forest Service 

Forest From Sawmill

Products

Laboratory

Research Scanner Error

Paper

FPL 459

David W. Lewis 
Abstract

Most, if not all, optical scanners being used in sawmills are 

to some degree imprecise, inaccurate, or both. This scanner 

error results in lost yield through choice of the “wrong” 

sawing pattern, i.e., a pattern optimal for either a smaller or 

larger diameter log. The study reported here quantifies these 

losses and leads to the following recommendations. 

(1) System designers should choose equipment and 

algorithms that minimize the possibility of measuring a log 

as being larger than it really is. 

(2) System designers and sawmill personnel should attempt 

to keep measuring error as small as reasonably possible, 

especially in sawmills cutting small-diameter, short, low taper 

logs; e.g. stud mills. 

(3) Anyone trying to determine the economic feasibility of 

achieving a particular level of scanner precision and 

accuracy in a specific sawmill can use this study as a

prototype for quantifying the losses in that mill. 

Keywords: Lumber, recovery, lumber yield, scanners, 

sawmilling, computer techniques, simulation, process 

control, automation, sawing patterns 

October 1985 

Lewis, David W. Yield losses from sawmill scanner error. Res. Pap. 

FPL 459. Madison, WI: U.S. Department of Agriculture, Forest Service, 

Forest Products Laboratory; 1985. 12 p. 

A limited number of free copies of this publication are available to the public 

from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 

53705. Laboratory publications are sent to over 1,000 libraries in the United 

States and elsewhere. 

The Laboratory is maintained in cooperation with the University of Wisconsin. 
Yield Losses 

From Sawmill 

Scanner Error 

David W. Lewis, Forest Products Technologist 

Forest Products Laboratory, Madison, WI 

Introduction

The sawmill industry is using automated control systems to 

augment or, in some cases, replace human observation and 

decisionmaking. The rapid implementation of these systems 

for primary log breakdown has resulted from technological 

advances in optical scanners, computers, and simulation 

modeling. Even though scanners have been greatly 

improved, most, if not all, of those being used in sawmills 

are to some degree imprecise, inaccurate, or both. This 

imprecision and/or inaccuracy results in lost yield through 

choice of the “wrong” sawing pattern, i.e., a pattern optimal 

for a larger or smaller diameter log. There is no information 

available quantifying these losses; and, because most 

automated log breakdown control systems give reasonable 

results, many people in the sawmill industry do not realize a

problem exists. Even where the problem has been 

recognized, without quantifying data it has been impossible 

to determine the economic feasibility of correcting it. 

The results of the study discussed in this paper quantify the 

losses in lumber recovery resulting when the ‘wrong” sawing 

pattern is used by an automated log breakdown control 

system. This information can be used by sawmill managers 

and equipment manufacturers in determining specifications 

for new systems or modifications to existing ones. 

Background

The basic elements of any automated control system include 

sensors, a decision model, actuators, and feedback. 

Sensors, such as optical scanners, measure the present 

state of the system. The decision model uses the 

information collected by the sensors and other data pertinent 

to the process being controlled to calculate the best 

processing decision, which actuators then implement. 

Finally, the results of the action are fed back for comparison 

with the processing decision or system variables. In 

closed-loop systems, the decision model uses feedback to 

automatically minimize variation in the results. In open-loop 

systems-which virtually all sawmill systems are-there is 

no automatic control. Instead the operator uses the feedback 

information to make adjustments in the system as he or she 

sees fit. 

In a typical automated log breakdown control system, 

scanners measure the length and diameters of a log and 

determine its position with respect to the processing system. 

The decision model uses this information-along with mill 

parameters such as kerf, sawing variation, and product 

values-to determine the saw set and log position giving the 

highest yield. Setworks move the log or the saws or both to 

their proper positions, and the log is then sawn. 

Usually the time required by the decision model to calculate 

the optimal sawing pattern and associated machine sets is 

too great to be able to make these calculations once the log 

has entered the processing system. Therefore, a primary log 

breakdown simulation model, such as the Best Opening 

Face (BOF) program (Lewis 1985), is used to calculate 

optimal sets for the entire expected range of logs, and these 

sets are stored in the control system computer. The model 

“looks up” the best set for each log based on the scanner 

measurements or operator decisions or both. 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - -

Methods

The ability of an automated log breakdown control system to 

maximize recovery from each log is only as good as the 

information provided by the scanners. This information can 

be degraded by scanner imprecision and/or inaccuracy and 

by the algorithms used to convert scanner measurements 

into log end diameters. 

Very little previous work has been published on the scanner 

error problem. Noffsinger (1979) found the accuracy of five 

different scanners ranged from 0.05 inch to 0.24 inch while 

the precision of the same scanners ranged from ±0.30 inch 

to ±2.14 inches. He did not consider how the scanner data 

might have affected lumber yields. No other work on this 

problem has been reported, although some mills may have 

developed proprietary information. 

Computer simulation models have been used to study 

similar related problems. For instance, Hallock et al. (1978, 

1978) and Stern et al. (1978) reported the relation of various 

sawing methods and sawing accuracy to lumber yield. In 

addition, the Sawmill Improvement Program (SIP) (Lunstrum 

1974) has been used to evaluate the operating efficiency of 

over 800 sawmills and gives accurate predictions of possible 

recovery gains. Sawmill experience has shown the results of 

these various types of studies using simulation models are 

valid and useful in predicting sawmill performance. This 

suggests that the results reported in this paper also 

represent actual sawmill situations. 

To study the effects of scanner error, I used the BOF model 

to simulate a well-operated North American sawmill 

converting small softwood logs into construction lumber. The 

logs, which the BOF model assumes are shaped like 

truncated cones, had small-end diameters ranging from 4.5 

to 20.5 inches in 0.05-inch increments. Log lengths from 8 to 

20 feet in 2-foot increments and taper from 1 to 5 inches per 

18 feet of log length in 1-inch increments were used. 

The sawmill parameters used, such as kerf, dressing 

allowance, and sawing variation (tables 1, 2), represented 

those used in the most advanced North American sawmills. 

These parameters were chosen after considering SIP 

studies, previous simulations (Hallock et al. 1976, 1978; 

Stern et al. 1978) and consultations with sawmill experts. 

The two most common North American sawing methods 

were simulated (fig. 1). Logs were broken down into lumber 

and cants using the split taper sawing method, with the 

sawlines parallel to the pith, or the full taper sawing method, 

with the sawlines parallel to one side of the log (Hallock 

et al. 1976). In both cases, the resulting cants were broken 

down using the full taper method with a variable fence. Both 

1- and 2-inch lumber were cut (table 2). However, the 1-inch 

lumber was cut only from the outside of the log and only 

when higher yield would result. 

Table 1.—Sawing parameters used in simulation 

Parameter Value

Head saw kerf

Resaw kerf

Narrowest nominal width

Shortest nominal length

Shrinkage

Wane allowance

0.165 inch 

0.134 inch 

4 inches 

8 feet 

3.3 percent 

25 percent 

Table 2.—Lumber sizes and associated allowances used in 

simulation

Nominal Dry Dressing Dressing Sawing Rough 

dressed allowance shrinkage variation green 

In.

Thickness

1 0.750 0.078 0.028 0.062 0.918

2 1.500 .078 .053 .062 1.693

Width

4 3.500 .078 .120 .109 3.807

6 5.500 .078 .187 .109 5.874

8 7.250 .078 .246 .125 7.698

10 9.250 .078 .313 .125 9.765

12 11.250 .078 .381 .125 11.833

2
Results

Even though use of the “wrong” sawing pattern results in 

loss of lumber recovery, it was not known whether this loss 

would be the same for all log diameters, lengths, and tapers. 

In order to quantify these effects the simulations were run in 

stages. Initially, 16-foot logs, 4.5 to 20.5 inches small-end 

diameter, with 2 inches of taper were considered. Each log 

was theoretically sawn by each sawing method using the 

BOF model and solutions based on maximum cubic 

recovery found. Then each log was theoretically sawn using 

sawing patterns for logs up to ±0.5 inch different in 

small-end diameter by 0.05-inch increments. Finally, the 

losses were calculated as a percentage of the BOF solution 

and the results plotted (fig. 2). Then sawing logs 8, 12, 16, 

and 20 feet in length, 4.5 to 20.5 inches in diameter, and 

with 2 inches of taper was simulated using both sawing 

methods. In addition, the sawing of logs 16 feet long, 4.5 to 

20.5 inches in diameter, with 1 and 3 inches of taper was 

simulated using the split taper sawing method. Finally, since 

it was apparent length and taper affected yield, the sawing 

of logs in all length and taper classes was simulated using 

both sawing methods. 

Figure 1.—Two methods of sawline orientation. (ML84 5623) 

Figure 2. —Yield losses resulting from log diameter measurement 

error for 16-foot logs with Pinch taper sawn by the split taper sawing method. One-inch-diameter c/asses from 5 to 20 inches are 

shown. (ML84 5617) 

Several relationships are evident from the data. For almost 

every log, use of large-log sawing patterns resulted in 

greater losses than use of small-log sawing patterns 

(figs. 2-7; app.). In many cases, the loss for a given 

increment of error was over twice as great when the larger 

sawing pattern was used. It can also be seen that losses are 

generally greater with the full taper sawing method than with 

the split taper method and that small-diameter, short, and/or 

low taper logs have greater losses than large-diameter, long, 

and/or high taper logs (figs. 3-7; app.). 

Sawing Methods 

The data for 16-foot, 6-inch-diameter logs show that with 

split taper sawing, choosing a pattern for a larger log results 

in a maximum loss of 13.7 percent, while choosing a pattern 

for a smaller log results in maximum losses of 7.9 percent 

(fig. 3). For 16-foot, 18-inch-diameter logs split taper sawing 

results in maximum losses of 4.8 and 3.1 percent when 

choosing larger and smaller patterns respectively. With full 

taper sawing maximum losses for 6-inch logs are 18.7 and 

13.2 percent while maximum losses for 18-inch logs are 

13.2 and 3.1 percent (fig. 4). 

Log Length 

Considering log length, the maximum losses when split taper 

sawing 8-foot, 8-inch-diameter logs are 20.3 and 

11.3 percent, while the maximum losses for 20-foot, 

8-inch-diameter logs are 8.4 and 4.7 percent (fig. 5). In 

comparison, the maximum losses for 8-foot, 

16-inch-diameter logs are 6.6 and 3.8 percent and for 

20-foot, 16-inch-diameter logs are 3.1 and 2.9 percent 

(fig. 6). 

Taper

The maximum losses when split taper sawing 16-foot logs 

with 1-inch taper are greater, 20.1 and 9.8 percent, than for 

16-foot logs with 3-inch taper, 10.5 and 6.1 percent, and for 

16-foot logs with 5-inch taper, 8.3 and 6.2 percent. 

The losses due to 0.1- and 0.2-inch errors in sawing pattern 

selection for logs of all lengths, all taper classes, and 

selected diameter classes sawn by both sawing methods 

can be seen in the appendix. Because the BOF model 

saved no lumber shorter than 8 feet in length (table 1), the 

losses for 8-foot logs are the same for all taper classes. 

3
Figure 3. —Yield losses resulting from log diameter measurement 

error for 16-foot logs with 2-inch taper sawn by the split taper sawing method. (ML84 5618) 

Figure 4.—Yield losses resulting from log diameter measurement 

error for 16-foot logs with 2-inch taper sawn by the full taper sawing 

method. (ML84 5619) 

Figure 5.—Yield losses resulting from log diameter measurement 

error for 9-inch-diameter logs with Finch taper sawn by the split 

taper sawing methods. (ML84 5620) 

Figure 6.—Yield losses resulting from log diameter measurement 

error for 15-inch-diameter logs with 2-inch taper sawn by the split 

taper sawing method. (ML84 5621) 

Figure 7.—Yield losses resulting from log diameter measurement 

error for 16-foot, 9-inch-diameter logs, sawn by the split taper sawing method. (ML84 5622) 

4
Conclusions Literature Cited 

Because the logs modeled are assumed to be truncated 

cones and because the results are at least partly dependent 

on the assumed sawing parameters and log distribution, 

caution should be used in applying these findings to any 

specific mill. In particular, determining the economic 

feasibility of achieving a certain level of scanner precision 

and accuracy is not possible with current data. The 

magnitude of the losses shown in the appendix indicate that 

if Noffsinger’s results (1979) are typical of the industry, the 

potential gains are large. 

Even with these constraints, I can make several 

recommendations based on the present data. 

(1) System designers should choose equipment and 

algorithms that minimize the possibility’ of measuring a log 

as being larger than it really is. 

(2) System designers and sawmill personnel should attempt 

to keep measuring error as small as reasonably possible, 

especially in sawmills cutting small-diameter, short, low taper 

logs; e.g. stud mills. 

(3) Anyone trying to determine the economic feasibility of 

achieving a particular level of scanner precision and 

accuracy in a specific sawmill can use this study as a

prototype for quantifying the losses in that mill. 

Hallock, Hiram; Stern, Abigail; Lewis, David W. Is

there a “best” sawing method? Res. Pap. FPL 280. Madison, 

WI: U.S. Department of Agriculture, Forest Service, Forest 

Products Laboratory; 1976. 12 p. 

Hallock, Hiram; Stern, Abigail; Lewis, David W. A look 

at centered vs offset sawing. Res. Pap. FPL 321. Madison, 

WI: U.S. Department of Agriculture, Forest Service, Forest 

Products Laboratory; 1978. 17 p. 

Lewis, David W. User’s guide to sawmill simulation and 

the Best Opening Face system. Gen. Tech. Rept. FPL ___. 

Madison, WI: US. Department of Agriculture, Forest 

Service, Forest Products Laboratory: 1985 (in press). 

Lunstrum, Stanford J. The sawmill improvement program. 

Southern Lumberman. 229(2848): 141-144; 1974. 

Noffsinger, J. R. St. Regis sawmill scanners-applications 

and accuracy. In: Electronics in the sawmill: Proceedings of 

the electronics workshop; 1979 March; Portland, OR. San 

Francisco: Miller Freeman Publishing Inc.; 1979: 42-45. 

Stern, Abigail; Hallock, Hiram; Lewis, David W. 

Improving sawing accuracy does help. Res. Pap. FPL 320. 

Madison, WI: U.S. Department of Agriculture, Forest 

Service, Forest Products Laboratory; 1978. 12 p. 

5
Appendix

Yield losses resulting from 0.1- and 0.2-inch errors in sawing 

pattern selection for logs of selected diameter classes are 

shown in the following tables. Because the BOF model 

saved no lumber shorter than 8 feet in length, the losses for 

8-foot logs are the same for all tapers. 

Table A-1.—Yield losses due to log diameter measurement error for 8-foot logs 

Split taper sawing method Full taper sawing method 

Diameter class Yield loss for error size Yield loss for error size 

-0.2 -0.1 +0.1 +0.2 -0.2 -0.1 +0.1 +0.2

In. - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - -

ALL TAPERS 

6 10.0 4.6 15.3 21.2 10.0 4.6 15.3 19.6

8 5.2 2.6 9.8 16.6 5.2 2.6 11.2 16.6

10 3.8 1.8 7.9 11.5 3.8 1.8 8.2 12.1

12 3.7 1.8 3.8 6.7 3.7 1.8 3.4 6.4

14 2.9 1.5 4.3 5.8 2.9 1.5 4.5 6.0

16 2.1 1.2 2.9 5.7 2.2 1.1 3.2 5.6

18 1.9 1.0 2.6 3.4 1.9 1.0 2.7 3.4

6
Table A-2.—Yield losses due to log diameter measurement error for 10-foot logs with various tapers 

Split taper sawing method Full taper sawing method 

Diameter class Yield loss for error size Yield loss for error size 

-0.2 -0.1 +0.1 +0.2 -0.2 -0.1 +0.1 +0.2

In. - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - -

1-INCH TAPER 

6 7.5 4.1 9.1 18.2 8.3 3.8 9.9 13.9

8 4.8 2.8 6.6 11.1 4.7 2.7 7.0 12.3

10 3.1 1.6 5.5 10.2 3.2 1.7 7.1 9.4

12 2.9 1.4 4.2 6.6 3.0 1.6 5.5 7.8

14 2.8 1.5 3.9 6.4 2.4 1.5 4.5 5.8

16 2.0 1.1 1.6 3.5 2.1 1.2 3.0 4.1

18 1.7 1.0 2.1 2.9 1.8 1.0 2.5 3.1

2-INCH TAPER 

6 7.8 3.7 13.1 15.6 8.9 4.2 12.8 17.8

8 5.0 2.6 6.3 12.0 5.1 2.5 7.7 14.3

10 3.9 2.1 4.7 8.8 3.9 1.9 6.4 10.4

12 2.6 1.6 4.9 6.6 3.2 1.6 4.8 8.0

14 2.5 1.5 2.9 4.5 2.8 1.5 4.6 6.3

16 1.9 1.1 2.3 3.1 2.4 1.2 3.0 5.0

18 1.8 1.0 1.8 2.5 1.7 1.0 2.1 2.7

3-INCH TAPER 

6 8.0 4.3 11.8 17.1 7.7 3.8 10.4 14.4

8 5.2 2.6 7.1 11.3 5.3 2.8 6.2 13.4

10 4.1 2.3 3.1 6.2 3.9 1.9 4.8 8.6

12 2.9 1.5 3.4 6.9 3.2 1.7 5.6 7.4

14 3.1 1.5 3.8 5.4 2.6 1.2 3.8 6.3

16 2.2 1.1 2.3 3.6 2.4 1.2 3.4 5.0

18 1.9 1.1 1.9 2.7 2.0 1.0 2.0 3.1

4-INCH TAPER 

6 7.5 4.5 9.4 12.5 8.3 4.0 9.5 13.9

8 4.7 2.3 6.3 10.4 4.8 2.1 7.6 13.5

10 3.9 2.1 4.6 7.3 3.8 1.8 5.5 8.7

12 2.9 1.4 3.5 6.4 3.2 1.6 5.3 6.7

14 2.8 1.5 4.2 5.5 2.8 1.2 4.3 6.7

16 2.3 1.1 3.0 4.7 2.0 1.1 3.5 4.4

18 1.6 .8 1.9 2.7 1.8 1.1 2.0 3.6

5-INCH TAPER 

6 7.9 3.9 7.2 13.2 8.2 3.5 7.4 17.8

8 4.7 2.5 8.1 9.7 4.5 2.4 6.9 11.5

10 3.5 1.9 5.1 9.8 3.6 1.9 5.8 9.2

12 3.1 1.5 4.8 8.1 3.1 1.5 4.1 6.6

14 2.7 1.5 4.0 5.8 2.4 1.3 3.2 4.5

16 2.0 1.0 3.3 4.8 2.1 1.1 3.2 5.0

18 1.7 .9 2.5 3.3 1.9 1.0 2.9 3.3

7
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Table A-3.—Yield losses due to log diameter measurement error for 12-foot logs with various tapers 

Split taper sawing method Full taper sawing method 

Diameter class Yield loss for error size Yield loss for error size 

-0.2 -0.1 +0.1 +0.2 -0.2 -0.1 +0.1 +0.2

In. Pct - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - -

1-INCH TAPER 

6 5.7 3.3 9.4 15.1 7.9 4.2 11.7 17.1

8 4.1 2.2 5.8 11.2 4.5 2.6 8.1 12.4

10 3.3 1.8 5.5 9.2 2.9 1.9 6.3 10.4

12 2.4 1.3 3.9 5.3 2.7 1.4 5.8 7.9

14 2.5 1.4 3.1 5.6 2.5 1.5 4.2 5.7

16 2.0 1.1 1.7 2.9 2.1 1.2 3.1 3.9

18 1.5 .8 1.5 2.5 1.6 1.0 2.1 2.8

2-INCH TAPER 

6 7.1 4.7 8.6 11.4 8.6 4.2 9.7 15.4

8 4.5 2.4 4.6 9.1 4.4 2.1 6.1 12.8

10 3.6 2.0 5.1 7.0 3.9 1.8 5.7 9.6

12 2.4 1.3 3.0 4.1 3.1 1.6 5.1 6.5

14 2.3 1.3 3.1 4.3 2.8 1.3 4.4 6.6

16 1.8 1.1 2.4 3.1 2.0 1.0 3.6 4.7

18 1.5 .9 2.0 2.5 1.6 1.0 2.0 2.8

3-INCH TAPER 

6 7.2 3.2 9.2 13.5 7.4 3.6 10.1 14.3

8 4.4 2.2 5.2 9.5 4.5 2.0 4.5 11.1

10 3.2 1.8 3.5 5.6 3.5 1.8 5.1 9.4

12 2.4 1.4 3.9 6.1 3.1 1.5 4.5 6.8

14 2.3 1.0 2.7 4.3 2.7 1.5 3.3 5.0

16 2.0 1.1 2.5 4.2 2.2 1.2 2.6 4.4

18 1.3 .9 1.7 2.6 1.7 1.0 2.2 2.9

4-INCH TAPER 

6 4.9 2.8 4.9 12.2 6.2 3.4 6.3 11.9

8 4.0 2.0 6.8 11.1 4.4 2.1 5.9 9.9

10 3.0 1.7 3.9 5.8 3.4 1.8 5.1 8.2

12 2.8 1.4 3.1 4.5 3.4 1.9 4.0 5.3

14 2.3 1.3 3.0 4.9 2.1 1.2 3.1 4.8

16 1.7 1.1 2.3 3.4 2.1 1.1 2.3 4.7

18 1.5 .9 2.2 2.9 1.6 .9 2.0 3.1

5-INCH TAPER 

6 4.7 2.6 6.7 9.8 5.8 2.8 7.4 14.4

8 3.0 1.7 5.8 9.2 4.4 2.3 6.0 8.8

10 3.3 1.7 4.1 6.1 3.0 1.7 4.9 6.6

12 2.7 1.1 4.3 6.1 2.7 1.5 4.3 5.7

14 2.6 1.5 3.1 5.4 2.4 1.3 2.8 4.7

16 2.0 1.2 3.0 3.6 2.0 1.1 2.2 3.6

18 1.7 1.0 2.1 3.1 1.8 .9 2.1 2.9

8
Table A-4.—Yield losses due to log diameter measurement error for 14-foot logs with various tapers 

Split taper sawing method Full taper sawing method 

Diameter class Yield loss for error size Yield loss for error size 

-0.2 -0.1 +0.1 +0.2 -0.2 -0.1 +0.1 +0.2

In. - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - -

1-INCH TAPER 

6 5.5 3.1 9.0 13.8 7.2 4.1 10.5 14.9

8 3.4 2.3 5.4 10.0 4.4 2.6 7.3 11.7

10 3.0 1.9 5.0 8.2 3.1 2.1 7.3 10.6

12 2.2 1.1 2.9 4.6 2.7 1.5 6.1 7.7

14 2.4 1.4 2.7 4.7 2.2 1.4 3.9 5.4

16 2.0 1.1 1.5 2.5 2.1 1.1 3.0 4.0

18 1.4 .8 1.6 2.3 1.6 .9 2.0 2.5

2-INCH TAPER 

6 5.9 3.8 7.7 11.7 7.7 3.9 8.3 13.1

8 4.5 2.5 4.5 8.1 4.3 2.2 8.1 12.1

10 2.5 1.7 3.4 5.5 3.9 1.9 5.1 9.3

12 1.7 1.3 4.2 5.5 2.5 1.4 4.4 6.2

14 2.0 1.4 2.9 4.1 2.8 1.4 3.8 5.5

16 1.4 1.0 2.0 2.9 1.9 1.0 3.2 4.6

18 1.3 .8 2.1 2.6 1.5 .9 1.9 2.7

3-INCH TAPER 

6 5.2 2.9 4.4 9.5 6.8 3.2 9.8 13.5

8 4.1 2.1 6.4 10.1 4.6 2.3 4.6 10.5

10 2.9 1.6 3.3 6.0 3.4 1.5 4.1 9.0

12 2.5 1.4 3.8 5.5 2.8 1.3 3.6 5.7

14 2.4 1.3 2.2 4.2 2.5 1.3 3.1 4.7

16 1.7 1.0 2.3 3.6 2.3 1.2 2.9 4.3

18 1.5 1.0 2.0 2.6 1.6 .9 2.1 2.7

4-INCH TAPER 

6 4.2 2.0 5.0 9.2 6.3 3.4 6.3 20.1

8 3.4 2.0 4.9 7.6 3.7 1.8 4.0 7.5

10 3.2 1.5 3.9 6.8 3.6 1.8 4.4 7.7

12 2.7 1.4 3.8 4.9 2.9 1.6 4.1 5.9

14 2.5 1.5 2.6 4.5 2.6 1.3 3.2 5.0

16 1.9 1.2 2.4 3.0 1.9 1.0 2.5 4.1

18 1.6 .9 2.3 2.3 1.9 1.0 2.3 2.9

5-INCH TAPER 

6 4.7 2.6 5.0 7.7 4.5 2.4 6.4 10.3

8 3.4 1.8 5.0 8.8 3.7 1.7 5.5 8.1

10 2.2 1.7 3.5 3.6 3.2 1.7 4.9 6.3

12 3.0 1.8 3.5 5.0 2.6 1.3 3.7 5.5

14 2.4 1.2 2.5 3.9 2.3 1.1 3.1 4.5

16 1.8 1.0 2.1 3.6 1.6 1.0 2.3 3.5

18 1.6 .8 2.0 2.3 1.7 .9 2.0 2.7

9
Table A-5.—Yield losses due to log diameter measurement error for 16-foot logs with various tapers 

Split taper sawing method Full taper sawing method 

Diameter class Yield loss for error size Yield loss for error size 

-0.2 -0.1 +0.1 +0.2 -0.2 -0.1 +0.1 +0.2

In. - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - -

1-INCH TAPER 

6 5.6 3.3 8.0 11.9 6.2 4.4 8.1 14.8

8 3.6 2.3 3.7 8.1 4.3 2.4 7.1 11.9

10 3.1 1.7 4.5 7.6 3.2 2.1 6.2 8.6

12 2.1 1.1 2.5 3.5 2.4 1.4 5.3 7.3

14 2.1 1.0 3.3 4.2 2.2 1.4 4.3 5.3

16 1.6 .8 1.7 2.6 1.7 1.1 3.4 4.2

18 1.3 .8 1.5 2.2 1.5 .9 1.8 2.5

2-INCH TAPER 

6 4.2 3.1 6.7 9.8 6.9 3.5 7.5 11.1

8 3.6 2.2 3.4 6.9 4.4 2.2 5.4 10.5

10 2.8 1.6 3.0 5.6 3.0 1.5 5.1 7.6

12 2.0 1.2 3.4 4.8 2.7 1.3 4.6 6.3

14 1.9 1.1 2.7 4.3 2.4 1.3 3.6 4.7

16 1.5 1.0 2.0 3.0 1.9 1.0 2.7 3.6

18 1.2 .8 1.5 2.1 1.4 .8 1.7 2.6

3-INCH TAPER 

6 4.6 2.5 3.9 9.1 6.3 3.6 6.0 15.8

8 3.5 1.9 5.0 7.9 3.6 1.6 4.2 7.9

10 3.3 1.8 3.5 7.0 3.4 1.7 4.9 7.7

12 2.4 1.3 3.6 4.6 2.5 1.2 3.6 5.7

14 2.2 1.4 2.4 4.0 2.3 1.3 2.5 4.4

16 1.9 1.1 2.2 2.9 2.1 1.1 2.4 4.2

18 1.3 .9 1.9 2.0 1.6 .9 2.2 2.6

4-INCH TAPER 

6 5.3 3.1 3.9 7.7 5.5 2.7 6.2 11.4

8 3.9 2.1 3.1 7.0 4.3 2.0 4.9 8.2

10 3.3 1.7 3.1 5.5 3.4 1.5 4.4 7.3

12 2.7 1.5 2.9 4.1 2.7 1.4 4.3 6.1

14 2.0 1.0 1.8 3.6 2.2 1.2 2.5 3.8

16 2.0 1.0 1.9 3.1 2.0 1.0 2.1 3.7

18 1.4 .9 1.7 2.2 1.7 .9 2.1 2.4

5-INCH TAPER 

6 4.9 2.6 4.3 7.8 4.8 3.2 4.2 16.3

8 3.7 1.8 4.3 6.8 3.3 1.5 4.7 7.7

10 1.6 1.7 2.7 2.7 3.0 1.7 3.7 6.2

12 2.5 1.5 2.9 3.7 2.4 1.1 2.8 4.5

14 2.1 1.2 2.0 3.7 2.3 1.1 3.1 4.0

16 2.1 1.2 2.0 2.8 2.0 1.1 2.5 3.7

18 1.6 .8 2.0 2.5 1.4 .8 1.8 2.4

10
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Table A-6.—Yield losses due to log diameter measurement error for 18-foot logs with various tapers 

Split taper sawing method Full taper sawing method 

Diameter class Yield loss for error size Yield loss for error size 

-0.2 -0.1 +0.1 +0.2 -0.2 -0.1 +0.1 +0.2

In. Pct Pct

1-INCH TAPER 

6 6.2 3.4 6.2 12.6 6.7 3.8 7.6 13.5

8 3.3 2.4 4.5 8.0 4.0 2.2 8.1 12.2

10 2.7 1.5 3.8 6.7 3.1 2.0 5.7 8.8

12 1.7 1.1 2.9 3.9 2.4 1.4 5.5 7.1

14 1.9 1.1 2.9 3.9 2.1 1.3 3.9 5.2

16 1.3 .7 1.6 2.3 1.8 1.0 3.2 4.1

18 1.2 .7 1.5 2.0 1.4 .8 1.9 2.8

2-INCH TAPER 

6 3.4 2.3 5.1 9.6 5.9 3.2 6.4 11.7

8 3.2 1.9 3.9 7.3 4.6 2.1 4.9 9.4

10 2.4 1.5 3.7 6.3 2.6 1.5 4.2 7.1

12 1.9 1.1 3.6 5.6 2.4 1.3 4.0 6.1

14 1.6 1.2 2.6 4.0 2.3 1.3 3.4 4.8

16 1.4 .9 2.2 3.1 1.8 1.0 2.7 4.0

18 1.4 .9 1.7 2.3 1.6 .9 2.0 2.4

3-INCH TAPER 

6 4.4 2.5 4.9 8.9 5.0 2.9 5.6 10.0

8 3.3 1.9 5.5 7.5 4.0 2.0 4.0 8.1

10 2.7 1.9 2.6 4.1 3.2 1.7 3.6 7.2

12 2.3 1.6 2.7 4.4 2.6 1.3 3.6 5.4

14 2.0 1.1 2.2 2.9 2.5 1.2 2.3 3.8

16 1.5 .9 1.5 2.4 1.8 .9 2.6 4.0

18 1.2 .7 1.6 2.0 1.6 .8 2.1 2.5

4-INCH TAPER 

6 5.6 2.9 3.0 5.6 5.1 2.8 7.1 18.6

8 3.6 1.9 3.1 5.4 3.5 1.7 4.3 8.7

10 2.6 1.3 2.5 4.2 3.1 1.4 3.9 7.3

12 2.4 1.3 2.4 3.9 2.5 1.3 3.5 4.9

14 1.6 .9 1.7 2.7 1.9 1.0 2.8 3.9

16 1.7 1.0 1.6 2.5 1.8 1.0 1.8 3.1

18 1.6 .9 1.6 2.3 1.6 .9 2.0 2.6

5-INCH TAPER 

6 4.9 2.8 2.9 4.3 4.6 2.9 5.6 9.6

8 2.6 1.6 4.0 5.0 3.1 1.8 4.2 5.6

10 2.2 1.7 3.0 3.1 2.8 1.4 2.8 5.5

12 2.3 1.2 2.8 4.0 2.3 1.3 2.6 4.2

14 2.2 1.1 1.9 3.2 1.9 1.1 2.3 2.6

16 1.8 .9 1.8 2.1 1.6 .8 2.0 2.7

18 1.5 .8 1.7 2.1 1.6 .9 1.7 2.6

11
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Table A-7.—Yield losses due to log diameter measurement error for 20-foot logs with various tapers 

Split taper sawing method Full taper sawing method 

Diameter class Yield loss for error size Yield loss for error size 

-0.2 -0.1 +0.1 +0.2 -0.2 -0.1 +0.1 +0.2

In. Pct - - - - - - - - - - - - - - - - - - - - - Pct - - - - - - - - - - - - - - - - - - - - -

1-INCH TAPER 

6 5.2 3.2 7.1 13.5 6.2 3.7 6.7 13.7

8 3.4 2.2 4.9 7.9 3.9 2.2 7.5 12.0

10 2.4 1.2 3.4 5.8 2.9 1.8 5.4 8.5

12 1.7 1.0 2.9 4.2 2.3 1.6 5.2 7.1

14 1.6 1.0 2.8 3.7 2.0 1.4 4.0 4.9

16 1.3 .7 1.6 2.5 1.7 1.0 3.2 4.1

18 1.3 .8 1.5 1.9 1.4 .8 2.0 2.7

2-INCH TAPER 

6 3.7 2.0 3.6 8.6 6.1 3.4 5.4 14.4

8 3.3 1.7 4.1 6.9 3.8 2.1 4.5 8.0

10 2.4 1.8 2.9 6.8 3.0 1.6 4.2 7.8

12 2.0 1.0 3.8 5.0 2.5 1.3 4.3 5.9

14 2.1 1.1 2.2 3.7 2.3 1.2 2.9 4.4

16 1.4 1.0 2.4 2.7 2.0 1.1 2.8 3.6

18 1.3 .9 1.9 1.9 1.6 .9 2.3 2.6

3-INCH TAPER 

6 5.7 2.9 2.8 6.6 5.0 2.4 6.1 12.9

8 2.6 1.4 3.3 6.3 3.9 2.0 3.6 7.2

10 2.6 1.3 2.3 4.1 3.2 1.8 4.7 7.2

12 2.3 1.3 2.6 3.7 2.4 1.3 4.1 5.4

14 2.1 1.0 2.6 3.4 2.0 1.1 2.2 4.0

16 1.4 .9 1.8 2.9 1.8 1.0 2.4 3.9

18 1.2 .7 1.4 1.8 1.5 .8 2.0 2.7

4-INCH TAPER 

6 4.9 2.8 4.1 6.4 4.0 2.0 4.5 6.4

8 3.2 1.8 3.4 5.4 3.3 1.8 4.2 7.5

10 2.6 1.4 1.8 3.2 2.6 1.4 3.1 5.3

12 2.3 1.2 2.4 3.8 2.3 1.2 2.8 3.9

14 1.6 1.0 2.2 3.1 2.1 1.1 2.1 3.4

16 1.1 .8 1.1 1.9 1.5 .8 2.1 2.8

18 1.4 .8 1.6 2.0 1.6 .8 1.8 2.2

5-INCH TAPER 

6 4.5 2.4 4.4 7.0 4.1 2.4 4.4 5.6

8 2.7 2.1 4.4 4.9 2.8 1.5 3.1 4.8

10 2.2 1.3 2.0 3.8 2.2 1.3 1.9 4.8

12 2.1 1.1 2.4 4.1 1.9 1.1 3.1 3.2

14 1.6 .9 1.9 2.5 1.8 1.0 2.3 2.7

16 1.5 .7 1.2 2.2 1.4 .8 1.5 2.9

18 1.2 .8 1.3 1.9 1.1 .6 1.4 2.3

2.5-10/85

12 U. S. GOVERNMENT PRlNTlNG OFFICE: 1985/641-044/20011 
The Forest Products 

Laboratory (USDA Forest 

Service) has served as the 

national center for wood 

utilization research since 

1910. The Laboratory, on the 

University of WisconsinMadison campus, has 

achieved worldwide 

recognition for its 

contribution to the knowledge 

and better use of wood. 

Early research at the 

Laboratory helped establish 

U.S. industries that produce 

pulp and paper, lumber, 

structural beams, plywood, 

particleboard and wood 

furniture, and other wood 

products. Studies now in 

progress provide a basis for 

more effective management 

and use of our timber 

resource by answering critical 

questions on its basic 

characteristics and on its 

conversion for use in a variety 

of consumer applications. 

Unanswered questions remain 

and new ones will arise 

because of changes in the 

timber resource and 

increased use of wood 

products. As we approach the 

21st Century, scientists at the 

Forest Products Laboratory 

will continue to meet the 

challenge posed by these 

questions.