United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

Research

Paper

FPL 437

Maximum Cutting

Yields for

6/4 Ponderosa Pine

Shop Lumber

KENT A. McDONALD

PAMELA J. GIESE

and

RICHARD O. WOODFIN
Abstract Acknowledgment

The moulding and millwork industries process nearly 1.3

billion board feet of Ponderosa Pine annually. Unfortunately,

thousands of trees are harvested unnecessarily to

compensate for inefficient processing. To help improve this

situation, researchers at the Forest Products Laboratory

developed maximum cutting yields for 6/4 Shop lumber in

grades No. 1 Shop, No. 2 Shop, and No. 3 Shop. Yields

were developed by building a representative 6/4 Shop

lumber data base and simulating sawing of the lumber by

the computer program OPTYLD. Results may be used to

compare cutting yields between 6/4 Shop grades, to guide

grade selection, and to estimate possible improvements in

processing decisions. Results also encourage more

automation in lumber processing.

The Timber Quality Research Project of the USDA Forest

Service Pacific Northwest Forest and Range Experiment

Station, Portland, Oreg., made a significant contribution to

the completion of this study through their assistance and

expertise.

This paper is part of a series on maximizing cutting yields

of 5/4 and 6/4 Shop, and 6/4 Vertical Grain lumber.
United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory1

Research

Paper

FPL 437

August 1983

Introduction

Maximum Cutting

Yields for

6/4 Ponderosa Pine

Shop Lumber

KENT A. MCDONALD, Research Forest Products Technologist

PAMELA J. GIESE, Computer Programmer

Forest Products Laboratory, Madison, Wisconsin

and

RICHARD O. WOODFIN, Forest Products Technologist

Pacific Northwest Forest and Range Experiment Station

Portland, Oregon

The losses that occur in the moulding and millwork industry

from inefficient cutting practices are not only costly to the

manufacturing operation but create a substantial and

unnecessary drain on the national timber resource. Each

year, an estimated 700 million board feet of timber are

removed from the resource base just to compensate for

inefficient processing. To foster better utilization of our

timber resource, we need to encourage the changes

necessary to update processing technology. Such updating

includes use of automated systems that locate lumber

defects, make processing decisions, and execute those

decisions through computer-controlled sawing systems. This

study was conducted to establish a foundation for

automation in the moulding and millwork industry. The first

objective was to build a representative data base of 5/4 and

6/4 Shop, and 6/4 Vertical Grain lumber presently being

used by the industry. The 6/4 No. 3 and Better Shop grade

data base was used for this report, which is the second of

a series (6,7).2The second objective was to simulate the

processing of this graded lumber with the computer

program OPTYLD (5) to obtain the maximum clear cutting

yield. Using the computer to evaluate every reasonable way

of ripping and crosscutting each board, maximum cutting

yields were developed that can be used to compare grade

output and to evaluate different processing methods.

The literature is void of any information that even closely

responds to these objectives. Previous attempts by

researchers to obtain cutting yield data based on factory

situations were hampered by the need to measure human

performance and ability, and by the problems inherent when

studying daily runs of lumber. Thus, individual board

contribution could not be analyzed nor could repeated trials

or alternative processing techniques be tried on the same

set of study material. Now, however, the use of board data

and the computer program OPTYLD enables repeated

cutting simulations without the operator’s biases affecting

results.

Study Procedure

Sampling

A sample of 6/4 No. 3 and Better Shop lumber was

collected over the geographical range of ponderosa pine

(fig. 1). Mill cooperators selected the lumber from their

inventories that they judged to be representative of their

suppliers. The cooperating mills were located in Oregon,

California, Arizona, and New Mexico. Because we decided

the sampling method used for 5/4 Shop (6) was too

cumbersome, a 10 percent systematic sampling method

was employed for the 6/4 Shop to broaden the sampling

base. Sample boards were obtained for measuring by

selecting every 10th board from a standard shipping unit.

This unit is defined as a strapped, dry, solid-stacked pile of

lumber that contains approximately 2,500 board feet

depending upon the length, width, and number of boards.

We actually selected 16.086 board feet of 6/4 No. 3 and

Better Shop lumber from numerous units. The volume

distribution of boards sampled by grade is shown in table 1.

All sample material was reinspected by Quality Supervisors

of the Western Wood Products Association to verify the

grade and scale. If an inspector determined a board was

misgraded, it was changed to the correct grade. We

numbered all sample boards and identified the grade, gross

surface measure, and net surface measure. We obtained

board measure for the 6/4 Shop lumber by the standard

procedure of multiplying net surface measure by 1.5.

1

 Maintained at Madison, Wis., in cooperation with the University of

Wisconsin.

2

 ltalicized numbers in parentheses refer to literature cited at end of this

report
Figure 1.—Distribution of ponderosa pine. (ML83 5059)

Figure 2.—Board measuring procedure. (M 148 959)

The actual widths and lengths of the boards sampled are

summarized in table 2. Of the 16,086 board feet of 6/4 No.

3 and Better Shop measured, lengths ranged from 6 to 16

feet. Approximately 85 percent of the lumber was 16 feet in

length. Sample board widths ranged from 5 to 24 inches,

with approximately half of the total volume less than 11

inches, one-third between 11 and 14 inches, and the

remaining one-sixth 15 to 24 inches wide (table 2).

Data Collection

A complete digital record was made of each selected board

and all defects, including type of defect and its location to

the nearest 1/4 inch. Board data recorded include board

number, grade, unit number, width, length, gross surface

measure, and net surface measure. Defects were measured

to the nearest 1/4 inch on both faces of each board (fig. 2)

using special measuring tables constructed for this purpose.

All defects were tallied by type and the four coordinate

points of a quadrilateral which contained the defect (fig. 3).

The complete area of each board face was classified as

either defect or clear to duplicate, as much as possible,

what would be expected from a functional, automated

lumber defect scanner. Any blemish not acceptable in a

clear cutting was classified as defect and recorded.

Multiple defects were grouped within a single quadrilateral

and assigned the code of the most predominant defect.

Interpretation of the final location of some defect

boundaries was necessary because the sampled lumber

was “oversized” in thickness. This proved important when

estimating the extent and severity of torn or chipped grain

that might “dress out” versus “persist” after normal

surfacing.

Simulated Board Processing

Program (OPTYLD)

To obtain the maximum clear cutting yields for making the

comparisons between grades of Shop lumber, we used the

computer program OPTYLD that Giese and McDonald (5)

developed specifically for this purpose. This computer

model simulates the three basic sawing operations–

multiple rip, crosscut, and rerip–typically used in

processing 6/4 Shop-graded lumber.

Constraints of this computer program to analyze the data

are:

-only clear, two-face cuttings can be obtained,

-1/4-inch increments used to describe board size, defect

coordinates, saw kerf, and cutting dimensions,

-maximum board size of 24 inches wide and 16 feet

long.

2
Figure 3.—Defect measuring procedure.

(M 148 955, M 148 954)

The computer model combines the board and defect data

of both board faces and selects the sawing solution that

results in the maximum value and/or yield of clear

cuttings. To obtain the best sawing solution, all valid

combinations of ripping then crosscutting are calculated

for each board, and the value or yield of clear cuttings

obtainable from these combinations is compared.

For the 6/4 Shop, we selected five cutting widths for

multiple ripping: 2.50, 3.00, 3.50, 4.50, and 4.75 inches.

These widths generally represent industry practice.

(Additional interpolations are necessary for widths not

selected.) Five rip saws were available for up to five rips,

plus a 1/4-inch edging allowance to straighten one edge

of each board. Random length cuttings were calculated9 inches and longer in increments of 1 inch, but not to

exceed 84 inches. To be consistent with present

processing practice, the reripping feature of the computer

program was used for calculating salvageable clear

material after the maximum ripping and crosscutting

solution was calculated. The reripping widths were 1.75,

2.50, 3.00, 3.50, and 4.50 inches. We developed a cutting

value index (table 3) to compare the value of different size

cuttings so that the highest return from each board could

be calculated. These values, which have no units,

represent current industry practice.

Table 1.—Sample data, 6/4 Ponderosa Pine Shop

Grade

Number

of

boards

Total

volume

Average

volume

per board

– – – – – – –Board feet1– – – – – –

No. 1 107 2,984 27.9

No. 2 346 8,136 23.5

No. 3 238 4,966 20.9

Combined 691 16,086 23.3

1

 Scaled net surface measure times 1.50.

Table 2.—Board size distribution, 6/4 Ponderosa Pine Shop

Board length Length distribution

Width

<16 feet 16 feet Total <16 feet 16 feet Total

In. – – – – –Board feet – – – – – – – – – – – –pct– – – – – – –

4-10 1,643 7,050 8,693 10 4 4 5 4

11-14 607 4,100 4,707 4 2 5 29

15-24 82 2,604 2,686 1 16 17

Total 2,332 13,754 16,086 15 8 5 —

Table 3.—Relative cutting value index, 6/4 Ponderosa Pine

Shop

Cutting length (in.)

Width

9-12 13-19 20-26 27-35 36-47 48-59 60-71 72-83 84

In. – – – – – – – – Value1

 per 1,000 square feet – – – – – – – –

2.50 800 810 820 840 860 880 1000 1030 1150

3.00 800 810 820 840 860 880 1000 1030 1150

3.50 810 830 840 860 880 910 1040 1070 1200

4.50 820 840 850 870 890 930 1080 1120 1250

4.75 825 845 855 875 895 950 1100 1145 1300

1

 Value has no units.

3
Methods and Results

Maximum Cutting Yield by Grade

The maximum clear cutting yields were computed for each

grade by computer simulation using a realistic set of mill

requirements. These maximum yields were compiled from

the individual board-by-board solutions that maximized the

value. Cutting values from the cutting value index were

used to make cutting solution decisions that would yield

larger cuttings. Individual board cutting solutions were

summarized for each grade by the number of cuttings, total

value of cuttings, yield per 1,000 board feet, percent cutting

area to board area. and total lineal feet of cuttings per

1,000 board feet (tables 4-8). Each summarization provides

results germane to different objectives. Mill managers and

operators can use these results to make production,

purchasing, and processing decisions, keeping in mind the

limitations previously mentioned. The actual number of

cuttings obtained from all boards by cutting width and

length classes are shown in table 4. These are maximum

yields that can only be expected for the sample of boards

used and the options used in the computer program.

Table 4.—Total clear cutting yield-piece count, 6/4 Ponderosa

Pine Shop

Length (in.)

Width

9-12 13-19 20-26 27-35 36-47 48-59 60-71 72-83 84

In. –––––––––––– No. of cuttings ––––––––––––

NO.1 SHOP

107 BOARDS, BOARD MEASURE = 2,984 BOARD FEET

1.75 76 59 19 8 5 4 3 1 2

2.50 81 111 81 109 74 62 45 32 70

3.00 35 39 35 28 35 24 21 7 33

3.50 35 49 36 34 38 26 30 28 49

4.50 29 31 31 34 21 16 16 9 43

4.75 13 28 20 28 22 9 5 7 34

NO.2 SHOP

346 BOARDS, BOARD MEASURE = 8,136 BOARD FEET

1.75 328 221 81 48 23 9 1 2 2

2.50 572 655 392 398 344 179 126 64 137

3.00 189 248 159 166 124 82 50 25 62

3.50 231 269 164 140 113 63 67 42 83

4.50 40 66 42 35 31 9 20 6 31

4.75 46 72 36 35 32 20 11 5 30

NO.3 SHOP

238 BOARDS, BOARD MEASURE = 4,966 BOARD FEET

1.75 322 199 53 26 15 1 0 1 0

2.50 468 605 389 264 198 95 60 29 30

3.00 179 215 134 91 83 36 29 15 19

3.50 134 189 104 70 56 23 17 8 18

4.50 26 40 12 22 9 9 13 2 4

4.75 33 25 25 11 12 8 1 1 2

Table 5.—Total clear cutting values, 6/4 Ponderosa Pine Shop

Length (in.)

Width

9-12 13-19 20-26 27-35 36-47 48-59 60-71 72-83 84

In. ––––––––––––––Value ––––––––––––––

NO.1 SHOP

107 BOARDS, TOTAL VALUE1 1,610

1.75 8 9 4 2 2 2 2 1 2

2.50 12 25 27 51 46 51 52 46 122

3.00 6 11 14 16 26 24 29 13 69

3.50 8 16 17 22 33 32 52 58 125

4.50 8 13 19 29 23 26 36 25 147

4.75 4 13 12 25 26 15 12 20 122

NO. 2 SHOP

346 BOARDS, TOTAL VALUE1 3,713

1.75 33 32 18 15 9 5 1 2 2

2.50 85 151 131 184 216 150 149 91 240

3.00 34 69 63 92 93 82 70 43 130

3.50 49 86 78 90 100 75 114 88 211

4.50 11 28 26 30 35 14 45 16 106

4.75 14 32 23 32 38 34 26 14 108

NO. 3 SHOP

238 BOARDS, TOTAL VALUE1 1,877

1.75 32 29 12 8 6 0 0 1 0

2.50 70 138 130 121 124 80 70 42 52

3.00 32 60 53 50 61 36 41 26 40

3.50 28 61 50 46 50 28 29 17 46

4.50 7 17 7 18 10 14 29 6 13

4.75 10 11 16 10 14 14 2 3 7

1

 Value has no units.

The actual accumulated value for each cutting width and

length class by grade is shown in table 5 and reflects the

relative cutting recovery by cutting size. Comparisons can

only be made within a grade as these are total values, not

values per unit board volume. This table is presented as an

example of the type of information available from the

computer program for those interested in determining the

effects of different processing options, a different value

table, or different kerf widths. For example, two different

sets of ripping widths can be directly compared after

running both through the computer program OPTYLD to

obtain the total clear cutting values.

Table 6 shows the number of cuttings per thousand board

feet. This table is consistent with the needs of mill

operators and managers where their inventory, sales, and

production records are on a board-measure basis. With this

table. cutting yields between lumber grades can be directly

compared. As these are maximum cutting yields from the

computer. they cannot be used as expected yields from a

conventional operation.
Cutting yields for cuttings other than those calculated in this

study can be estimated from table 6. However, only

minimum yields are then obtainable. For example, in table 6

for No. 1 Shop, the 11.4 cuttings 4.75 by 84 inches will

make at least twice that many cuttings 37 to 42 inches

long. Naturally, shorter cuttings cannot be summed to get

longer cuttings, nor can cuttings less than 9 inches in length

be counted as usable material because of computer

constraints. Widths also can be subdivided similarly to

lengths, but only in multiples or fractions of widths shown.

The distribution of clear cuttings recovered by grade is

obtained from the total cutting area within a size class as a

percent of the total area of the boards (table 7). Maximum

cutting volumes expected by cutting size by grade are

calculated directly from these percentages. For example,

46.3 board feet (4.63/100 × 1,000) of the 4.75- by 84-inch

cuttings could be expected from 1,000 board feet of No. 1

Shop, whereas 1,000 board feet of No. 2 Shop would yield

only 14.9 board feet (1.49/100 × 1,000) of the same

cutting. The relative distribution of the required cuttings of a

cutting bill from a grade can also be obtained for best grade

recovery and raw material selection.

Table 6.—Cutting yield to board measure, 6/4 Ponderosa Pine

Shop

Length (in.)

Width

9-12 13-19 20-26 27-35 36-47 48-59 60-71 72-83 84

in. – – – – – – – – Cuttings per 1,000 board feet – – – – – – – –

NO. 1 SHOP

107 BOARDS, BOARD MEASURE = 2,984 BOARD FEET

1.75 25.5 19.8 6.4 2.7 1.7 1.3 1.0 0.3 0.7

2.50 27.2 37.2 27.2 36.5 24.8 20.8 15.1 10.7 23.5

3.00 11.7 13.1 11.7 9.4 11.7 8.0 7.0 2.4 11.1

3.50 11.7 16.4 12.1 11.4 12.7 8.7 10.1 9.4 16.4

4.50 9.7 10.4 10.4 11.4 7.0 5.4 5.4 3.0 14.4

4.75 4.4 9.4 6.7 9.4 7.4 3.0 1.7 2.4 11.4

NO. 2 SHOP

346 BOARDS, BOARD MEASURE = 8,136 BOARD FEET

1.75 40.3 27.2 10.0 5.9 2.8 1.1 0.1 0.2 0.2

2.50 70.3 80.5 48.2 48.9 42.3 22.0 15.5 7.9 16.8

3.00 23.2 30.5 19.5 20.4 15.2 10.1 6.2 3.1 7.6

3.50 28.4 33.1 20.2 17.2 13.9 7.7 8.2 5.2 10.2

4.50 4.9 8.1 5.2 4.3 3.8 1.1 2.5 .7 3.8

4.75 5.6 8.8 4.4 4.3 3.9 2.5 1.4 .6 3.7

NO. 3 SHOP

238 BOARDS, BOARD MEASURE = 4,966 BOARD FEET

1.75 64.8 40.1 10.7 5.2 3.0 0.2 0.0 0.2 0.0

2.50 94.2 121.8 78.3 53.2 39.9 19.1 12.1 5.8 6.0

3.00 36.0 43.3 27.0 18.3 16.7 7.2 5.8 3.0 3.8

3.50 27.0 38.0 20.9 14.1 11.3 4.6 3.4 1.6 3.6

4.50 5.2 8.0 2.4 4.4 1.8 1.8 2.6 .4 .8

4.75 6.6 5.0 5.0 2.2 2.4 1.6 .2 .2 .4

Table 7.—Cutting size distribution, 6/4 Ponderosa Pine Shop

Length (in.)

Width

9-12 13-19 20-26 27-35 36-47 48-59 60-71 72-83 84

In. –––––Cutting area as a percent of board area –––––

NO. 1 SHOP

107 BOARDS, TOTAL BOARD AREA = 2,036 SQUARE FEET1

1.75 0.48 0.55 0.26 0.15 0.12 0.12 0.11 0.05 0.10

2.50 .72 1.48 1.56 2.89 2.57 2.78 2.46 2.12 5.01

3.00 .39 .66 .85 .91 1.48 1.28 1.39 .58 2.84

3.50 .45 .94 .98 1.27 1.85 1.72 2.37 2.56 4.91

4.50 .49 .78 1.07 1.64 1.29 1.32 1.60 1.06 5.54

4.75 .23 .76 .72 1.40 1.46 .78 .52 .87 4.63

NO. 2 SHOP

346 BOARDS, TOTAL BOARD AREA = 5,566 SQUARE FEET1

1.75 0.75 0.74 0.40 0.32 0.20 0.10 0.01 0.03 0.04

2.50 1.89 3.27 2.80 3.85 4.41 2.96 2.58 1.54 3.59

3.00 .75 1.49 1.35 1.92 1.91 1.63 1.22 .72 1.95

3.50 1.08 1.84 1.65 1.85 2.02 1.45 1.91 1.41 3.04

4.50 .24 .59 .54 .61 .70 .27 .73 .25 1.46

4.75 .29 .68 .48 .65 .77 .64 .42 .23 1.49

NO. 3 SHOP

238 BOARDS, TOTAL BOARD AREA = 3,413 SQUARE FEET1

1.75 1.21 1.09 0.43 0.28 0.22 0.02 0.00 0.03 0.00

2.50 2.53 4.89 4.53 4.13 4.14 2.57 1.98 1.14 1.28

3.00 1.16 2.11 1.87 1.71 2.04 1.16 1.15 .71 .97

3.50 1.02 2.13 1.71 1.55 1.63 .88 .78 .44 1.08

4.50 .25 .58 .25 .61 .34 .42 .78 .14 .31

4.75 .34 .38 .54 .32 .46 .42 .06 .07 .16

1

 Board area determined from board coordinates and is not the

same as scaled surface measure.

Total lineal feet of the random length cuttings by grade and

width per 1,000 board feet are shown in table 8. These

results include the rerip yield and were determined by

summing the individual cutting lengths. Again, the relative

differences and similarities that occur between the three

Shop grades are shown in this table. The lineal footage

data are used to evaluate different computer runs where

cutting options are being compared.

Maximum Cutting Yield by Board Size

Because the maximum cutting yield is available for each

board in the Ponderosa Pine data base, the results are

presented by board size for the three Shop grades. The

yield of clear cuttings from any given board depends on the

size and location of clear areas and the size of the board.

Because the timber resource is changing to smaller

diameter, second-growth trees, more narrow width lumber

is being processed. The effect on the moulding and millwork

industries is lower yields and smaller cuttings.

The percent of maximum cutting yields shows relatively little

difference as surface measure (board size) changes within

each grade. Individual board percentages and average

percentage plotted for each surface measure show the total

variation in the board data and the increased variation from

No. 1 to No. 3 Shop (figs. 4-6).

5
Board value, plotted against surface measure (figs. 7-9)

shows the correlation between low-value small boards and

high-value large boards. This is a direct result of the size

and number of clear cuttings these boards can produce.

Individual board values and average value plotted for each

surface measure show the total variation by board and the

relative difference between the grades. The effect of

changing board size can be determined by resampling a

Shop grade, calculating board surface measure, and

estimating yield and value from these data.

Recovery

The differences that occur between the Shop grades of 6/4

lumber are evident from the value obtained per unit area of

cuttings, the recovery percentages, and the computed

cutting values per board measure as they are shown in

table 9. Because the raw material for the moulding and

millwork industry is purchased on a per 1,000 board feet

basis, the resulting cutting values obtained from the study

boards are shown based on the same measure.

(Remember, these values have no units and are derived

using values from the cutting value index) (table 3).

The value per unit of clear cuttings obtained for each grade

is calculated by:

Table 8.—Total lineal feet of cuttings to board measure, 8/4

Ponderosa Pine Shop

Width No. 1 No. 2 No. 3

In. – – – – –Lineal feet per 1,000 board feet – – – – –

1.75 91 122 154

2.50 708 883 897

3.00 283 354 354

3.50 399 381 264

4.50 269 99 68

4.75 196 98 48

Table 9.—Recovery from 6/4 Ponderosa Pine Shop

Shop Total Total Total Value1 Recovery Cutting

grade board value of area of par unit cutting value1

measure cuttings cuttings cutting area to per 1,000

board board

measure feet

Board

feet

No. 1 2,984 1,610 1,570 1.025 52.6 540

No. 2 8,136 3,713 3,882 .956 47.7 456

No. 3 4,966 1,877 2,082 .902 41.9 378

where V = total value of clear cuttings

A = total board area in clear cuttings (ft2)

UV = value per unit of clear cutting

For each grade, these values are 1.025 for No. 1, 0.956 for

No. 2, and 0.902 for No. 3. These values do not vary

greatly but do reflect the cutting sizes and cutting values

obtained by grade.

Recovery of clear cuttings relative to the board footage in

the sample is obtained by:

where A = total board area in clear cuttings (ft2)

B = board feet

R = percent recovery of cutting area to board feet

By grade, maximum recovery percents are 52.6 for No. 1,

47.7 for No. 2, and 41.9 for No. 3 Shop. These percentages

reflect differences due to grading rules applied by the

grading association. To convert these values to percent

recovery of cuttings in board feet, multiply the percentages

by 1.5.

Finally, the cutting value expected for 1,000 board feet is

calculated by:

where R = percent recovery (from eq. [2])

UV = value per unit of clear cutting (from eq. [1])

V/M = value per 1,000 board feet

By grade, values per 1,000 board feet are 540 for No. 1,

456 for No. 2, and 378 for No. 3. Assuming the relative

value index table used was reasonably accurate, these

cutting values should represent the absolute differences in

yields between these grades. The actual value recovered by

an individual operation may be substantially different from

these figures, due to processing methods and acceptance

of other than clear cuttings.

Reripping

In most millwork and moulding operations, the primary

breakdown of lumber to obtain clear cuttings involves

ripping lumber full length followed by crosscutting. After

crosscutting, all material is then either a clear cutting or

classed as defective. The defective material may contain

clear areas that meet or exceed the minimum clear cutting

size but are unobtainable by the rip, then crosscut,

operations. These areas can be salvaged by an additional

ripping operation, called reripping, or backripping. Usually

the crosscut operator identifies the salvage pieces, cuts

them to length, and sends them to the rerip operation.

1

 Value has no units (see table 5).

6

Summary

Results presented so far in this report have been the

combined rip and rerip clear cutting yields. The reripping

results are shown as the number of rerip cuttings obtained

per 1,000 board feet by cutting size (table 10). The rerip

widths include the narrower 1.75-inch width. The

significance of a reripping operation shows up in the rerip

results in both additional volume and value (table 11).

Cutting yield increases of 3.6 to 7.3 percent of the total

cutting yield and value increases of 2.8 to 6.6 percent were

directly attributable to the reripping operation.

Table 10.—Rerip yield to board measure, 6/4 Ponderosa Pine

Shop

Length (in.)

Width

9-12 13-19 20-26 27-35 36-47 48-59 60-71 72-83 84

In. – – – – – –Rerip cuttings per 1,000 board feet – – – – – –

NO. 1 SHOP

107 BOARDS, BOARD MEASURE = 2,984 BOARD FEET

1.75 25.5 19.8 6.4 2.7 1.7 1.3 1.0 0.3 0.7

2.50 3.7 3.7 .3 1.0 .0 .3 .0 .0 .0

3.00 1.7 .7 .0 .0 .0 .0 .0 .0 .0

3.50 3.0 2.0 .3 .0 .0 .0 .0 .0 .0

4.50 .0 .0 .0 .0 .0 .0 .0 .0 .0

4.75 — — — — — — — — —

NO. 2 SHOP

346 BOARDS, BOARD MEASURE = 8,136 BOARD FEET

1.75 40.3 27.2 10.0 5.9 2.8 1.1 0.1 0.2 0.2

2.50 7.1 3.3 1.0 .5 .4 .0 .0 .0 .0

3.00 5.0 2.5 .1 .2 .2 .0 .0 .0 .0

3.50 2.1 1.1 .1 .1 .1 .0 .0 .0 .0

4.50 .0 .0 .0 .0 .0 .0 .0 .0 .0

4.75 — — — — — — — — —

NO. 3 SHOP

238 BOARDS, BOARD MEASURE = 4,966 BOARD FEET

1.75 64.8 40.1 10.7 5.2 3.0 0.2 0.0 0.2 0.0

2.50 9.1 5.2 1.8 1.0 .6 .0 .0 .0 .2

3.00 4.6 2.0 .2 .4 .2 .0 .0 .0 .0

3.50 1.8 1.2 .4 .0 .0 .0 .0 .0 .0

4.50 .0 .0 .0 .0 .0 .0 .0 .0 .0

4.75 — — — — — — — — —

Table 11.—Rip and rerip yield summary, 6/4 Ponderosa Pine

Shop

Shop Maximum cutting yield

grade Rip Rerip Rerip

Ft2Ft2

Pct

No. 1 1,514 56 3.6

No. 2 3,683 199 5.1

No. 3 1,928 153 7.3

1

 Value has no units (see table 5).

Value

Rip Rerip Rerip

(1) (

1 ) Pct

1,565 45 2.8

3,551 162 4.4

1,753 124 6.6

Completion of this yield study provides original clear cutting

yield information by grade for 6/4 Shop lumber. Because

these yields were obtained by the computer, the production

decisions were consistent and are free from human biases

and problems inherent when studying daily runs of lumber.

An example of applying this information could be a mill

operator’s decision to forego the common practice of

processing a mixture of No. 3 and Better Shop lumber, and

instead processing a straight No. 3 Shop and putting the

No. 1 and No. 2 Shop back on the market for a higher

return.

This study also provides an extensive data base for 6/4

Shop boards. This data base will encourage more study of

improved utilization methods and the testing of these

methods on the same boards. Such tests consist of

evaluating alternative products and processes, including an

ongoing evaluation of automated defect detection. We hope

that researchers and managers will realize, through this

series of reports, the value of the currently available tools in

pursuing improved utilization.

Any improved utilization practices implemented will foster

significant savings in timber resources. Timber annually lost

to inefficient processing is a resource wasted which must

be replaced with other growing stock of the same or a

substitute species.

2 •5-9183

8
Literature Cited

McDonald, Kent A.; Geise, Pamela J.; Woodfin, Richard O.

Maximum cutting yields for 6/4 Ponderosa Shop lumber.

USDA Forest Serv. Res. Pap. FPL 437. Madison, WI:

Forest Products Laboratory; 1983

Less than optimum utilization of Ponderosa Pine 6/4 Shop lumber causes

unnecessary losses to the timber resource. From a representative lumber data

base and simulation of the lumber sawing process, the maximum clear cutting

yield for 6/4 Shop lumber was determined using the computer program OPTYLD.

Processors of Shop lumber can compare their yields with the computer yields by

lumber grade. can improve grade selection, and can estimate improvements in

processing.

Keywords: Maximum cutting yields, multiple ripping, Shop grades,

moulding and millwork, sawing simulation, computer processing,

utilization research.

U. S. GOVERNMENT PRINTING OFFICE: 1 9 8 3 6 5 4 0 2 5 4 0 1 5 9