United States Power Consumption and Lumber Aariculture - 

Forest Service Yields for Reduced-Kerf Circu 

Northeastern Forest Saws CU ing Hardwoods 

Experiment Station 

Research 

Paper N E-505 Donald G. Cuppett 
The Author 

Donald G. Cuppett received his 

bachelor of science degree in forestry from West Virginia University 

in 1950. In 1950-52 he served as a 

farm forester for the West Virginia 

State Forestry Department, and in 

1953-54 as assistant state forester. 

In 1955 he joined the Union Carbide 

Corporation as a forester, becoming 

department head in 1958, a position 

he held until 1962, when he joined 

the staff of the Northeastern Forest 

Experiment Station, Forestry Sciences Laboratory, at Princeton, 

West Virginia, as research forester 

and project leader. 

Manuscript received 

for publication 7 January 1982 

Abstract 

Two 50-inch diameter headsaws 

were used for sawing (a) hardwood 

cants into boards, and (b) hardwood 

bolts into pallet parts. One saw had 

a 9x10 gage plate with 114-inch kerf 

teeth, and the other had a 7x8 gage 

plate with 9132-inch kerf teeth. Power consumption for the two saws 

was determined with a watt-hour 

meter, measuring power used for 

paired cuts in 6-inch thick hardwood 

cants. Product yields for the two 

saws were compared by sawing 

matched samples of hardwood bolts 

into pallet parts. The 114-inch kerf 

saw consumed an average of 15 percent less power than the 9132-inch 

kerf saw. Product yield for the 114- 

inch kerf saw averaged 8 percent 

more than yield for the 9132-inch 

kerf saw. Both power consumption 

and product yield differences for 

the two saws were highly significant. 
Introduction 

Most sawmills designed for 

small hardwoods use circular saws. 

The most commonly used circular 

headsaws have 7x8 gage plates (7 

gage or 3116-inch eye thickness and 

8 gage or 5132-inch rim thickness), 

with 17164- or 9132-inch kerf teeth. 

Some circular resaws are equipped 

with 3116-inch kerf carbide-tooth 

saws, but many have standard tooth 

saws as heavy as 6 gage (1 3164-inch 

thickness) with up to 318-inch kerf 

teeth. Scragg and bolter mills are 

frequently equipped with 6x7 gage 

saws having 5116- to 318-inch kerf 

teeth. 

Relatively thick saws have been 

used for hardwoods because thick 

saws perform better than thinner 

saws under sustained heavy loads, 

and because the thick saws require 

less skilled maintenance, advantages that have been judged to offset their lower product yield and 

higher power consumption. But increasing timber and energy costs 

have renewed interest in reducing 

kerf losses in hardwood sawmills. 

Past research in the use of thinkerf saws for hardwoods is scanty. 

Telford (1949) analyzed the effects 

of 11 factors on the power required 

to operate 7x8 gage saws cutting 

10-inch thick cants. He found that 

with other factors constant the cutting torque required for different 

kerf widths was as follows: 

8132-inch kerf: 1,028 Ib-inches 

9132-inch kerf: 1,460 Ib-inches 

10132-inch kerf: 1,600 Ib-inches 

Although cutting torque was 

least for the 8132-inch teeth, sawing 

was not sustained long enough to 

determine whether extended operation with 8132-inch teeth would be 

successful. In 1954, Telford reported 

that a 118-inch difference in kerf results in a difference of approximately 10 percent in board yield per log. 

During studies of product 

yields from low-grade logs and 

bolts, we operated a 50-inch diameter 7x8 gage saw with 8132-inch kerf 

teeth for extended periods. Mixed 

hardwood logs including oak and 

hickory up to 16 inches in scaling 

diameter were sawn into 414-inch 

boards without saw heating or faulty 

board sizing. Four- and six-foot 

bolts up to 14 inches scaling diameter were sawn into cants and side 

lumber with similar results. It appeared that kerf could be significantly reduced in commercial hardwood sawmills processing small 

logs or bolts. In this report we compare power consumption and product yields of a 7x8 gage, 9132-inch 

kerf saw with those of a 9x10 gage, 

114-inch kerf saw processing hardwood bolts. 

were selected for the power consumption tests; woods-run sound 

bolts having 1-inch or less absolute 

sweep were used for the product 

yield comparisons. Three species 

groups were included: the oaks, yellow-poplar-cucumber, and beechbirch-maple. 

Two 50-inch diameter circular 

saws with 44 "F" style teeth were 

obtained for the study. The saws 

were made by the same firm, and 

were identical except for plate thickness and kerf width. Sawing was 

done on a mobile sawmill having a 

four-block manual carriage and 4- 

inch belt feedworks. The saw mandrel is turned at 600 rlmin by a 50- 

horsepower electric motor. 

Power Consumption Experiment 

Procedure Three lines were cut with each 

saw on 20 or more 6-inch thick 

Four- and six-foot-long bolts cants for each species group. 

from thinning hardwood poletimber Paired cuts, one with each saw, 

stands were used for the experi- were made at the sides and near the 

ment. Clear or nearly clear bolts pith of each cant (Fig. 1). Saw cuts 

A = 7 x 8 GAGE SAW CUTS (9/32" KERF) 

B = 9 x10 GAGE SAW CUTS f 1/4Ii KERF) 

6" x 10" CANT (CROSS SECTION) 

Figure 1 .-Diagram of the end cross-section of a cant, showing placement of experimental saw cuts. 
were placed as close together as 

possible to minimize differences in 

wood density for the matched saw 

cuts. First cuts on the sides of the 

cants were alternated between the 

two saws. 

A separate saw was used for 

producing the cants used in the 

power consumption test. For the initial species group, the new teeth on 

each test saw were ground lightly to 

remove damage caused in shipment. After each species group was 

sawn, the teeth were reground to 

establish sharp tooth corners, but 

the teeth were not side-dressed. 

Power consumption for the individual saw cuts was measured by 

a portable watt-var recorder' (Fig. 2). 

Differences in power consumption 

for the two saws on matched cuts 

were analyzed by paired t-tests. 

Product Yield Experiment 

Bolts for the product yield comparison were sorted by species 

groups, numbered, and measured as 

follows: average d.i.b. (diameter inside bark) to nearest 1110-inch on 

both ends, length to nearest 1110- 

inch, and absolute sweep to nearest 

112-inch. This information was used 

to separate the bolts into samples 

matched by species, diameter, 

length, cubic volume, and sweep 

class for the two saws. 

Sample bolts were sawn into 

standard dimension pallet deckboards and stringers on both test 

saws. Saws were sharpened at the 

beginning of each species group 

run. No intermediate sharpening 

was required. Teeth were ground on 

the faces only, just enough to reestablish sharp corners. Sawing pat- 

$ General Electric CH-11. 

The use of trade, firm, or corporation 

names in this publication is for the information and convenience of the 

reader. Such use does not constitute 

an official endorsement or approval 

by the U.S. Department of Agriculture 

or the Forest Service of any product 

or service to the exclusion of others 

that may be suitable. 

Figure 2.-Portable watt-var recorder used for measuring eieclric power 

consum~tion of saws. 
Table 1 Comparison of power c~ns~~impf ion far 9x8 gage, 9132-inch 

kerf saw versus a Sx"% gage, 8132-inch kerf saw 

for cutting 6-inch thick cants 

Species Type cart 

cuts 

Per 

saw 

t ndex of 

power consumed 

9/32" 8/32" 

kerf kerf 

% additional 

power 

for 

9/32'' 

ke rC 

saw saw saw 

tld f 

Yellow-poplar Plain 52 5.105 4.500 13.4 9,047151 

Yellow-poplar Quartered 26 2.455 2.050 19.7 5.552125 

Oaks Plain 30 6.245 5.470 14.1 7.657129 

Oaks Quartered 45 3.4911) 2,960 18.9 6.221114 

Beech-BirchMaple Plain 36 9.010 7.390 21.9 9.468135 

Beech-BirehMaple Quartered "r 5.090 4.270 19.2 6.071117 

Figure 3.---Watt-var recorder chart ~iluskrating relative power consump- tion for two pairs OF matched cuts on a maple cant. Saw gage is marked 

at the apex sf the stylus mark for each cut. Shaded areas ind~cate the 

amount of power consumed for each saw chit. 

THICK SAW 

(7X 8 GAGE! 

terns for the two saws were identical and simulated the patterns used 

on Scragg mills; i.e., 4-inch thick 

cants were cut from bolt centers; 

and the resulting cants and slabs 

were resawn into stringers and 

deckboards. Four-inch opening 

faces were cut on 6-, 7-, and &inchdiameter bolts; 6-inch opening faces 

were cut on 9-inch and larger bolts. 

Differences in parts yields from 

the sample bolts processed by the 

two saws were analyzed by analysis 

of covariance, with the midpoint 

bolt diameter as the covariate. 

Results 

Power Consumption Experiment 

Relative power consumptions 

for the two saws are shown in Table 

1. They include both the power used 

to cut the wood and power to operate the carriage feed. The power 

consumption index is the planimetered area (in square inches) contained between the base line and 

the stylus mark on the recorder 

chart for each saw cut (Fig. 3). Table 

1 index values are the sums of 

THICK SAW 

(7x8 GAGE)* 

THIN SAW 
planimetered areas for all saw cuts 

with each saw, by species and type 

of cut. 

The 9132-inch kerf saw required 

from 13.4 percent to 21.9 percent 

more power than the 8132-inch kerf 

saw, depending on species and type 

of cut. By t-tests, power consumption differences for the two saws 

were significant at the 0.001 level 

for all species and type-of-cut 

groups (Table 1). 

Some of the sample cants contained knots, and there were some 

slight differences in knot sizes for 

the paired saw cuts. Also, it was impossible to maintain identical feed 

speeds for the two saws in all 

paired cuts. Since both knot size 

and feed speed influence power 

consumption, a separate comparison of power consumption for the 

two saws was made between paired 

cuts in clear wood or where knot diameters were equal, and where feed 

speeds for the paired cuts varied by 

not more than 6 feet per minute 

(limit of recorder accuracy), The 

9132-inch kerf saw required from 

14.7 to 19.2 percent more power 

than the 8132-inch kerf saw, depending on species. Power consumption 

differences for the two saws were 

significant at the 0.001 level for all 

species groups (Table 2). 

Product Yield Comparison 

Table 3 shows a summary of 

volume and size data for the 

matched bolt samples used for comparing product yields for the two 

saws. Scaling diameters were almost perfectly matched. The sample 

match by cubic-foot volume shows 

a slight advantage for the 114-inch 

saw; most of the difference occurred in 6-foot yellow-poplar bolts, 

where the sample bolt volume for 

the 114-inch kerf saw was 0.57 cubic 

feet (about 0.6 percent) higher than 

for the 9132-inch kerf saw. Sample 

bolts ranged from 6 to 13 inches in 

scaling diameter; average scaling diameter was about 8.2 inches for the 

yellow-poplar, '7.0 inches for the 

oaks, and 7.6 inches for beechbirch-maple bolts. 

Product yields for the 114-inch 

kerf saw exceeded yields for the 

9132-inch kerf saw by an average of 

8.1 percent in board-foot volume 

and 8.0 percent in cubic-foot volume 

(Table 4). Yield gain for the 114-inch 

kerf saw was slightly higher for the 

oak and beech-birch-maple bolts 

than for the yellow-poplar bolts, 

probably because the sample yellow-poplar bolts contained less 

sweep and averaged about 1 inch 

larger in scaling diameter than the 

oak and beech-birch-maple bolts. 

Covariance analysis showed 

that yield differences between the 

two saws were highly significant for 

all species groups: 

Species Group F value PR>F d f 

Yellow-poplar 4-foot bolts 14.44 0.0002 1 

Yellow-poplar 6-foot bolts 16.13 0.0002 1 

Oaks 4-foot bolts 10.27 0.001 0 1 

Beech-birch-maple 4-foot bolts 8.23 0.0046 1 
Table 2. Power consumption comparison for 7x8 gage, 9/32-inch kerf 

and 9x10 gage, l/4=inch kerf saws cutting clear or equally 

knotty wood at identical feed speeds 

Species 

Average power 

Type saw consumption Standard 

index error 

% additional 

power for 

9/32-i nc h 

kerf saw 

Yellow-poplar 8132" kerf 

9/32" kerf 

Difference 

Oaks 8/32" kerf 

9/32" kerf 

Difference 

Beech-birch-maple 8/32" kerf 

9132" kerf 

Difference - 

* ** Statistically significant at the 0.001 level. 

Table 3.-Sample bolt matching data for product yield comparison 

Species group 

9/32" kerf saw 114" kerf saw 

Bolt 

length Sum of Volume Bolts Sum of Volume scaling scaling 

diameters diameters 

Yellow-poplar 

Yellow-poplar 

Oaks 

Beec h-Birch-Maple 

ft No. inches ft3 No. inches ft3 

Totals 1 90 1,463.8 294.18 1 90 1,463.9 294.87 

Table 4. Product yields for a 7x8 gage, 9132-inch kerf saw versus a 9x10 gage, 

114-inch kerf saw for cutting hardwood bolts into pallet parts 

Species Bolt Product yields Yield gain for 114" 

length 9/32" kerf saw 114" kerf saw 

kerf saw 

Yellow-poplar 

Yellow-poplar 

Oaks 

Beech-Birch-Maple 

Totals 2,075.56 138.72 2,243.99 149.81 168.4318.1 11.0918.0 
Discussion 

The study results indicate that 

significant savings in power consumption-slightly more than 15 

percent-can be achieved by a 1132- 

inch reduction in saw kerf. In commercial operations, this saving 

would apply to power consumed by 

saws and feed mechanisms during 

use; power required for saw and 

feed system idling, and for conveyors, debarkers, or other auxiliary 

equipment would not be affected. 

But since actual sawing operations 

account for a large portion of total 

power consumption in most sawmills, the power saved by a 1132- 

inch kerf reduction should be significant. 

Product yield averaged about 8 

percent more for the 114-inch kerf 

saw than for the 9132-inch kerf saw. 

The economic effect of such yield 

gains on commercial sawing operations would be substantial. For example, a mill producing 3 million 

board feet per year of pallet parts 

would realize an additional 240 thousand board feet of parts from the 

same volume of raw material, and at 

little added cost. At a parts value of 

$1 50 per thousand board feet, the 

additional production would be 

worth $36,000 per year. 

Application 

Commercial feasibility of using 

thin kerf saws will depend on saw 

performance in sustained production, and on the degree and cost of 

maintenance required for the thin 

saws. During the study, the 9x10 

gage 114-inch kerf saw performed as 

well as the thicker saw under identical operating conditions and maintenance. But the duration of sawing 

was too brief to conclude that results would be similar in commercial operation. We have, however, 

made extensive use of 7x8 gage 

saws with 114-inch kerf teeth for 

sawing both hardwood bolts and 

small sawlogs; the saws performed 

satisfactorily with normal maintenance. 

Two pilot tests will be conducted to evaluate the performance 

of 9x10 gage saws under long-term 

use. In one test, the saw will be 

fitted with 7132-inch kerf teeth (minimum theoretical kerf width for the 

9x10 gage saw) and used for sawing 

hardwood bolts into pallet parts. For 

the second test, a 9x10 gage saw 

will be used by a commercial operator for sawing woods-run sawlogs 

into standard lumber. Saw performance and maintenance requirements will be compared with those 

of the thicker saws normally used. 

Literature Cited 

Telford, C. J. Energy requirements 

for insert-point circular headsaws. 

Madison, WI: Forest Products Research Society Preprint; 1949. 

14 p. 

Telford, C. J., Small sawmills: a 

pocket guide. Agric. Handb. 70. 

Washington, DC: U.S. Department 

of Agriculture; 1954.26 p. 
Cuppett, Donald G. Power consumption and lumber yields for 

reduced-kerf circular saws cutting hardwoods. Broomat I, PA: 

Northeast. For. Exp. Stn.; 1982; USDA For. Serv. Wes. Pap. 

A 9x10 gage, 114-inch kerf saw and a 7x8 gage, 9132-inch kerf saw 

were used for cutting matched samples of hardwood cants and 

bolts into pallet parts. The 114-inch kerf saw consumed about 15 

percent less power than the 114-inch kerf saw. Product yield for 

the 114-inch kerf saw averaged 8 percent more than yield for the 

9132-inch kerf saw. 

ODC 1822.33-01 5.7]:176.1 

Keywords: Headsaw performance; conversion efficiency; paliiel 

- U.S. GOVERNNENT PRINTIXG OFFICE: 1982-505-012:22 
Headquarters of the Northeastern Forest Experiment Station are in 

Broomall, Pa. Field laboratories are maintained at: 

* Amherst, Massachusetts, in cooperation with the University of 

Massachusetts. * Berea, Kentucky, in cooperation with Berea College. * Burlington, Vermont, in cooperation with the University of 

Vermont. 

Delaware, Ohio. * Durham, New Hampshire, in cooperation with the University of 

New Hampshire. 

@ Hamden, Connecticut, in cooperation with Yale University. 

Morgantown, West Virginia, in cooperation with West Virginia 

University, Morgantown. * Orono, Maine, in cooperation with the University of Maine, 

Orono. * Parsons, West Virginia. 

@ Princeton, West Virginia. 

Syracuse, New York, in cooperation with the State University of 

New York College of Environmental Sciences and Foredry at 

Syracuse University, Syracuse. 

0 University Park, Pennsylvania, in cooperation with the 

Pennsylvania State University. 

Warren, Pennsylvania.