UNITED STATES DEPARTMENT OF AGRICULTURE . FOREST SERVICE . FOREST PRODUCTS LABORATORY . MADISON, WIS

USING THE FPL HARDWOODVENEER GRADES

FPL-025

DECEMBER 1963

SUMMARY

This Research Note contains basic information and essential instructions in the use of the recommended FPL hardwood veneer grades for the development of hardwood veneer log grades. Various characteristics and defects encountered in veneer grading are illus-trated and described, showing the influence of each on the grade classification that may be assigned.

USING THE FPL HARDWOOD VENEER GRADES

The U.

BY

HENRY H. HASKELL, Technologist

Forest Products Laboratory, Forest Service 1

U.S. Department of Agriculture

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Introduction

S. Forest Products Laboratory has developed and evaluated a hardwood veneer grading system that can be used to develop grades for hardwood veneer logs and bolts. Research Paper FPL-9 presents a comprehensive description of the recommended veneer grading system, and data obtained from studies conducted at four veneer mills to evaluate the performance of the recommended veneer grades. This Research Note has been prepared to supplement FPL-9, and presents instructions in the use of the grades, and illustrates the various Characteristics and defects encountered in hardwood veneer grading.

2

The FPL veneer grading rules accurately segregate veneer into three quality classes that reflect value. They are systematic, effective, easy to apply, and should foster uni-formity of grading.

In veneer, characteristics are repeated and the need for clipping at certain defects can be anticipated. There are also continual changes, and alertness to them is of prime impor-tance as the green veneer comes from the lathe or slicer, for accuracy of grading depends on the correct and consistent identification of characteristics and defects encountered.

1 Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 2 Henley, J. W., Woodfin, R. O., Jr., and Haskell, H. H. Recommended veneer grades for the development of

hardwood veneer log grades. U.S. Forest Serv. Res. Paper FPL-9, 12 pp., illus. Forest Products Laboratory, Madison, Wis. Oct. 1963.

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Preparatory Guide Rules

Adherence to the following guide rules is essential to effective use and application of the FPL hardwood veneer grades:

1. Practice Grading--Don’t wait until the study bolts are in the lathe to start to learn veneer grading.

2. Know the Veneer Characteristics.--Practically all the veneer characteristics that will be encountered are illustrated in this guide. Study them and interpret them the same each time they are seen. Make sure every member of the grading team interprets each characteristic the same.

When a characteristic not described in this report is encountered, relate it to known characteristics. Determine whether it is open or tight, rough, decayed, stained, or has distorted grain, Then use the same grade limitations as for known characteristics.

3. Usable Veneer.--A piece of veneer to be considered for the FPL grades A, B, and C must be at least 6 inches wide with unbroken (sound) edges.

4. Eliminating Defects.--Any opening 1/64 inch or less in width, except splits, may be clipped out with a single cut of a clipper knife. No residue allowance need be made for such a characteristic. Larger openings and splits may be included in lower grades of veneer, or if chipped out must be recorded as producing a piece of residue at least 1 inch wide.

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5. No Trim Allowance.--Do not anticipate, allow for, or include a trim allowance on a piece of veneer.

6. Mismanufacture.--Characteristics introduced by faulty manufacturing degrade the veneer just as do natural characteristics. Examples of mismanufacture are roughness, thick and thin veneer, scratches, rub marks, and “washboardy” veneer. Most of these characteristics will cause the veneer to become residue. If a significant portion (about 10 percent) of the veneer from a bolt is mismanufactured, the bolt should be eliminated from the study.

7. Measure.--Don’t guess at sizes of characteristics or widths of pieces of veneer--measure them.

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3 All veneer that does not meet the specifications for grades A, B, and C is termed “residue.” 4 Fiehl, O., and Godin, V. Peeling defects in veneer, their causes and control. Technical Note No. 25.

Canada, Dept. of Forestry, Forest Prod. Res. Branch. 1962.

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8. Quality, Not Quantity.--Grade for the maximum amount of the best quality veneer in the bolt--even in narrow widths. Remember, the primary objective is to develop good hardwood veneer log and bolt grades.

Description of Terms Used in the Grades

The description of terms used in the recommended FPL veneer grades, and also the specifications for each grade, as set forth in Research Paper FPL-9, are as follows: 2

Grading Defects

A defect, as used here, is defined as any irregularity occurring in or on wood that adversely affects its appearance, strength, durability, or utility values. The defects specifically recognized in these grades are described below. When characteristics not described in these grading specifications are encountered they will be considered in relation to described defects according to their adverse effect on appearance, strength, durability, or utility values of the veneer.

The following characteristics are grading defects and their presence is limited by the grading specific at ions :

Brashness.--A condition of wood characterized by low shock resistance for the species and by abrupt failure across the grain without splintering when the piece is bent only a small amount.

Cross break (figs. 1 and 2).--Separation of the wood cells across the grain of the veneer piece; usually accompanied by splintering.

Decay(fig. 3).--A disintegration of the wood substance due to the action of wood-destroying fungi. Decay that has not proceeded far enough to soften or otherwise per-ceptibly impair the hardness of the wood but usually accompanied by a slight discolor-ation or bleaching that gives the wood a dull and liefless appearance is termed incipient decay. However, it is not recognized as a separate grading defect.

Gum spots (fig. 4).--Well-defined accumulations of solid gum that occur between dis-placed wood elements. Sound gum spots have no openings larger than 1/64 inch. An open gum spot has an opening larger than 1/64 inch.

Holes .--Openings resulting from mechanical damage.

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Knots.--Cross or longitudinal sections of limbs with grain running at about right angles to the grain of the veneer of which they are a part. Knot size is determined by the char-acter of the grain of the knot and is measured at the points where the grain of the knot is most differentiated from that of the surrounding wood. Knots are measured to the nearest one-quarter inch and further classified into two groups:

(1) Sound knots (figs. 5 and 6) are solid and firmly fixed in the piece of veneer of which they are a part. Sound knots have no openings or pith larger than 1/64 inch.

(2) Open knots (figs. 7 and 8) or knotholes are voids where a portion of or all of the knot has dropped out. This includes knots with checks and pith wider than 1/64 inch.

Open insect damage(figs. 9 and lo).--Holes, grooves, or passages in the wood that are caused by the movements of insects.

Rough veneer(figs. 11, 12, and 13).--Veneerthat is not smoothly cut and will not pro-duce a smooth surface when one-quarter of the veneer thickness is removed by sanding. Roughness may occur as the result of naturalfeatures of the wood or by mismanufacture.

Splits.--Separations of the wood fibers parallel to the grain of the wood. Separations occurring as a result of “checking” or “shake” are classified as splits. A tight split (fig. 14) is one not wider than 1/64 inch. An open split (fig. 15) is one that is more than 1/64 inch wide.

Permissible Characteristics

The following are characteristics permitted by the grading specifications and not con-sidered to be, grading defects:

Distorted pain, burls (figs. 16, 17, 18, 19, 20, and 21).--Swirls or twists in the grain of the wood, generally rounded in outline, and usually resulting from overgrowth of dead branch stubs. Such areas do not contain a knot or a pith center.

Sound discolorations, stain(figs. 22, 23, 24, and 25).--A sound, firm part of the veneer where color varying from the natural cast of the veneer is evident and is caused by sap stain, mineral stain or streak, gum, water stain, chemical stains such as iron stain, or oil drips. See A(c1ear) grade for the only limitations on mineral stain or streak.

Sound insect damage(figs. 26 and 27).--Insect damage that is completely and firmly filled with frass and pith. Refer to A(clear) grade specifications for the only limitation on sound insect damage.

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A (Clear) Grade

Veneer in this grade must be smooth and free of defects. Distorted grain(burls) is permitted. Sound discolorations (stain) and sound insect damage are permitted with the following limitations: mineral stain or streak and sound insect damage may not be over 1/16 inch wide by 1/2 inch long, and must be at least 21 inches from any other mineral stain or streak or sound insect damage.

B (Sound) Grade

Veneer in this grade must be smooth and free of open defects. This grade admits dis-torted grain, sound discolorations, and sound insect damage, as in grade A but without limitation of size or number. In addition, sound knots up to 3/4 inch in average diameter, sound gum spots, and tight splits are permitted.

Larger knots and splits, open knots and large knot holes, decay, brashness, cross breaks, holes, and roughness are not permitted.

C (Utility and Back) Grade

Veneer in C grade may contain the defects of the B grade. In addition, there may be open knots, knot holes, holes, or open insect damage up to 2 inches in maximum diameter for a single hole or a group of holes up to 4 inches in aggregate diameter in any 12-inch-square area. Knots that contain decay are permitted if the surrounding wood is sound and the knot holes plus the decayed area meet the size limitations for open knots or knot holes.

Cross breaks and roughness are permitted if their largest dimension does not exceed 2 inches.

Splits up to 1 inch wide at the widest point shall be admitted if they are one-fourth or less the length of the veneer sheet. Splits 1/2 inch wide at the widest point may not be over one-half the veneer length. Splits 1/4 inch wide at the widest point may be over one-half the veneer length.

Larger knots, splits, holes, cross breaks, roughness, open insect damage, and decayed areas are not permitted.

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Specifications for Recommended Hardwood Veneer Grades

Cutting and Grading the Veneer

Cutting the Veneer

The first veneer peeled from a bolt by the lathe is called “roundup.” As veneer bolts are seldom perfectly cylindrical or without taper, the roundup consists of pieces varying in length, width, and shape. These pieces are usually discarded by a mill until they become the full length of the veneer bolt and at least 6 inches wide and of uniform full thickness.

A piece of veneer to be salvaged drops into a green chain and is conveyed to a clipper where the edges are squared. When a continuous sheet of veneer is peeled from the bolt, the veneer is rolled on a reel or run out on the conveyor system to the clipper.

The veneer is then clipped into widths by the clipperman to recover the grade and sizes required by the mill. By his actions the clipperman decides the grade recovery of the mill. For veneer grade recovery studies, it is therefore necessary to grade the veneer or select the veneer sample before it reaches the clipperman.

Grading the Veneer

The sample sheets of veneer are marked for the graders’ attention by a person stationed at the lathe. The first sample marked for grading is the first piece of veneer at least 6 inches wide, in full thickness, and the full length of the bolt. When the bolt has been rounded up, the sample consists of a sheet of veneer having a length equal to the circum-ference of the bolt.

The Forest Service grader stations himself in front of the clipperman, and equipped with tape and keel, begins to measure the samples and calls out the yield of veneer to an assistant responsible for recording the data. Typical grading sheets of veneer are shown in figures 28 through 36.

When grading samples of veneer which are less than a full circumference of the bolt (figs. 28 and 29), grading should begin at one edge of the sheet and continue across the width, accounting for each change of grade. The first step is to establish a sound, straight edge to the sample, which may be done by drawing or assuming a line on the sample. The line should run the full spurred length of the piece and be parallel to the long axis of the veneer bolt.

FPL-025 -6-

A sound edge means one that is free of splits, decay, and open defects. A sound defect firmly fixed in the veneer is permitted in a sound edge, provided such a defect is permitted in the particular grade to be assigned the piece in which it is located. Residue veneer is not required to have sound edges.

Grading samples that are pieces formed by the whole circumference of the bolt, are handled somewhat differently (figs. 30 through 33). It must be decided where in the sample grading should begin to obtain the maximum grade yield. In effect, grade the sample as though it were a continuous cylinder of veneer--not a flat sheet. For example, begin grading on one side of a defect and proceed around the sample. Do not begin to grade in the middle of a clear area of veneer, as this may result in two pieces of clear veneer too narrow to be classified except as residue.

Scan the sheet systematically. The grade of one portion changes when a characteristic is encountered that cannot be permitted in a better grade. At this point measure the width of the piece, and call off the width and grade to the recorder, Thus, in effect, the sheet has been “mentally clipped.’’

The objective is to get the best possible grades of veneer from each piece of the veneer sample. If, for example, in a piece of veneer 11 inches wide, there are five consecutive inches that have defects permitted in C grade, and the adjoining 6 inches are clear, call off the grade as 5 inches of residue and 6 inches of A grade,--not 11 inches of C grade.

When grading out a defect to upgrade the adjoining pieces of veneer, it may be found that the residue piece needs only to be 1/2 inch wide. Remember that the width of all pieces is recorded in whole inches, and this piece of residue is then “1 inch” wide for record purposes. The width of the adjoining pieces, however, may be measured to the actual limit of the defect.

It may be tempting to ignore defects near the end of a veneer sheet because the bolt may have a length trim allowance. However, they must not be ignored, and are important in the establishment of hardwood veneer log and bolt grades.

Examples of grading sheets of sliced veneer are shown in figures 34, 35, and 36. The grading procedure is much the same as for rotary cut veneer bolts of less than a complete circumference in length.

Recording the Veneer Grades

The width of each piece of veneer is first called out and then its’ grade (for example, 6 inches of A, 10 inches of B, etc.). Every piece of veneer in the sampling unit must be accounted for.

FPL-0 2 5 -7-

The recorder enters this information in appropriate columns on the tally form (fig. 37), using a separate line for each piece of veneer called out, including residue.

Cutting Back

Many hardwood veneer and plywood mills make use of roundup “fishtails.” They may also cut back in length pieces of defective veneer to recover short clear pieces. Therefore, all pieces should be examined for upgrading, including residue. Rotary cut veneer and sliced veneer are handled in the same way.

For the purpose of veneer grade recovery studies, most of the veneer poorer than grade A can be cut back in length to upgrade it. This should be done in even foot intervals of length down to and including 4 feet. The cutback piece may come from anywhere within the sheet as long as it is in one piece (fig. 36). The width of the piece is established in the first grading. For cutting back, only the length may be reduced.

First, the width and grade of the piece prior to cutback is called out, then the cutback length and grade. For example, 6 inches of C cut back to 5 feet of A. The recorder enters this information all on a single line of the tally form as shown in figure 37.

Dry Grading

The FPL veneer grades described are recommended for use with green veneer. How-ever, the veneer may be regraded after it is clipped and dried. First grade the piece as clipped.

The next step in dry grading is to establish a straight, sound edge to the piece, as described in the section “Grading the Veneer,” and then measure and record the cuttings, as in green grading. Five inches is the minimum permissible width of a piece of veneer in the dry condition.

In recording this data, the width and grade of the entire piece is first entered, and then, under this entry, the individual pieces that could be cut from the sheet to recover the maximum grades of the best veneer according to the recommended FPL hardwood veneer grades.

FPL-025 -8- .7-36

Figure 1.--The cut across the grain of the veneer was caused by an ax cut on the bolt. This and cross breaks less than 2 inches long are per-mitted on “C” grade veneer. The cut illus-trated is about 3 inches long, and would not be permitted in any grade of veneer. Species: Yellow birch.

M 123 997

M 124 378

Figure 2.- This cross break in the log. It is less than 2 the grain of the veneer, and in “C” grade veneer. Speci

occurred naturally inches long across would be permitted es: Yellow birch.

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Figure 3.--The dark streaks are areas They would not be permitted in any veneer. Species: Yellow-poplar.

of decay. grade of

M 125 990

M 123 988

Figure 4.--This veneer shows a gum spot. Because of its large size, it would only be permitted in “B” and “C” grade veneer. Itwouldbe per-mitted in “A” grade veneer if 1/16 inch wide or less. Species: Yellow-poplar.

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Figure 5.--This small sound knot has an opening less than 1/64 inch wide across the grain of the sheet of veneer. This defect would be per-mitted in “B” grade veneer. Species: Yellow-poplar.

M 123 971

M 124 392

Figure 6.--This knot is sound and would be per-mitted in ‘‘B” grade veneer. Species: Yellow-poplar.

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Figure 7.--This open knot would“C” grade veneer. Species:

be permitted inYellow-poplar.

M 123 991

Figure 8--The open knot in the center and the open bark pockets to the right of it would be allowed in “C” grade veneer. Species: Yellow birch.

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M 124 389

Figure 9.--This open insect damage consists of holes and a groove, It is permitted in “C”grade veneer. Species: Yellow birch.

M 124 317

M 124 387

Figure 10.--The open insect damage was caused by the Columbian timber beetle Corthylus columbianus. The discoloration associated with the holes was caused by a fungus. The defect would be permitted in “C” grade veneer. Species: Soft maple.

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Figure 11.--This area of roughness on veneer 1/8 inch thick would be permitted in “A” grade veneer. The depressions are less than one-fourth the thickness of the veneer. Species: Yellow-poplar.

M 123 984

M 123 987

Figure 12.--This area of roughness on veneer 1/8 inch thick would not be permitted in anyveneer grade. The depressions are more than the max-imum one-fourth the thickness of the veneer permitted in “A” and “B” grades, and the length and width are too great for “C” grade veneer. Species: Yellow birch.

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Figure 13.--This defect is a scar with intergrown bark. It would be considered to have the same effect on veneer as roughness. It is too long and too deep to be permitted in any grade veneer, and would be clipped out as residue. Species: Yellow birch.

M 124 375

M 124 384

Figure 14.--The edges of this tight split are very close together. The split is less than 1/64 inch wide and would be permitted in “B” grade veneer. Species: Yellow-poplar.

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Figure 15.--The edges of this open split will not close together when the veneer is made to lie flat. The split is wider than 1/64 inch and would be permitted in “C” grade veneer. Species: Yellow birch.

M 123 976

Figure 16.--This small area of distorted grain (burl) has a split less than 1/64 inch wide. The defect would be permitted in “B” grade veneer. Species: Yellow-poplar.

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M 124 382

Figure 17.--This area of distorted grain(burl) shows several short, tight splits less than 1/64 inch wide. These defects would be permitted in “B” grade veneer. Species: Yellow-poplar.

M 123 972

M 123 993

Figure 18.--This distorted grain may be the scar over grub damage or an injury. It is a defect because of the bark pocket in the center. The defect would be permitted in “B” grade veneer. Species: Yellow birch.

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Figure 19.--This photograph shows an area of distorted grain(burl) in the center and two smaller ones to the top. The distorted grain is without splits or pith and would bepermitted in “A” grade veneer. Species: Yellow-poplar.

M 123 975

M 123 992

Figure 20.--This streak of distorted grain (burls) is without splits or unsoundness. It would be permitted in “A” grade veneer. Species: Yellow birch.

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Figure 21.--This distorted grain (burl) is caused by bird peck. They are without splits or pith and would be permitted in “A” grade veneer. Species: Yellow-poplar.

M 124 390

M 124 385

Figure 22.--This sound discoloration is a mineral streak. It is too long(over 1 / 2 inch) to be per-mitted in “A” grade veneer. It would be per-mitted in ‘‘B” grade veneer. Species: Yellow-poplar.

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Fgure 23.--This veneer shows sound discolor-ation due to gum(areas of small, dark spots) and at a wound. The gum discolorations would not be permitted in veneer above “B” grade because of their closeness to each other. The wound discolorations would be permitted in “A” grade veneer except for the splits, which are wider than 1/64 inch. Species: Water tupelo.

M 92127 F

M 124 391

Figure 24.--This piece of veneer shows a brown-colored sound discoloration of unknown origin. This stain would be permitted in “A” grade veneer. Species: Red alder.

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Figure 25.--This piece of veneer shows a typical blue-black sound discoloration (iron stain) caused by the veneer lathe pressure bar tem-porarily resting at this point during veneer cutting. This would be permitted in “A” grade veneer. Species: Yellow birch.

M 124 381

M 124 252

Figure 26.--This veneer shows sound insect damage due to the movement of insect larvae in the cambium of the tree. This defect would be permitted in ‘‘B” grade veneer. Species: Soft maple.

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Figure 27.--The sound insect damage consists of numerous small dark pith flecks. They would be allowed in “B” grade veneer. Species: Yellow birch.

M 123 995

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M 123 957

Figure 28.--This sheet of veneer is roundup from the outer portion of a veneer bolt, and is less than one complete circumference of. the bolt. The edges were clipped square to simplify grading. The sheet has a large hole as the result of a depression in the bolt at this point. The veneer is also rough and contains cross breaks due to ax cuts. The dark line is a shadow caused by a change in the thickness of the veneer at this point due to the application of nosebar pressure. Species: Yellow birch.

Grade this sheet of veneer for practice before turning to figure 29.

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M 123 950

Figure 29.--This is the same sheet of veneer shown in figure 28. The entire sheet has been marked as residue as no narrower or shorter pieces of better grade veneer can be cut from it.

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M 125 043

Figure 30.--This sheet of veneer includes one complete circumference of a veneer bolt. The limits of the sample can be established by using the open knot located near the bottom of the sheet of veneer. The veneer contains open splits, open knots, and a mineral streak. Species: Yellow birch.

Grade this sheet of veneer for practice before turning to figure 31.

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M 125 039

Figure 31.--This is the same sheet of veneer shown in figure 30. The black lines show how the grader established the limits of the sample, and marked the grades of the pieces of veneer which could be cut from it, The piece marked “A” is 7 inches wide and contains no defects, The piece marked “B” is 8 inches wide and contains a mineral streak and a small tight knot. The piece marked “X” is residue because it is only 3 inches wide. The defects contained in “X” are open knots and splits which would be permiteed in C grade veneer. Species: Yellow birch.

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M 125 036

Figure 32.--This sheet of veneer is from the same bolt as the veneer shown in figure 29. This sample was taken from nearer the pith of the bolt and includes one complete circumference of a veneer bolt. The limits of the sample can be established by using the open knot located near the bottom of the sheet of veneer.

The sheet contains open splits and open khots.

Grade this sheet of veneer for practice before turning to figure 33.

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M 125 035

Figure 33.--This is the same sheet of veneer shown in figure 32. The black lines show that the limits of the sample include one complete revolution from the veneer bolt. The entire sample is marked as “C” grade veneer as no narrower or shorter pieces of higher grade veneer can be marked out.

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M 125 038

Figure 34.--Each sheet of flat-sliced veneer is a sample taken at a one-inch interval of flitch thick-ness. The sheet on the left was taken near the bark side of the flitch and the sheet on the right from the pith side near the backboard of the flitch.

The sheets have discolorations, distorted grain, open knots, and tight knots and splits. Species: Red alder.

Grade these sheets of veneer for practice before turning to figure 35.

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M 125 041

Figure 35.--These are the same sheets of veneer shown in figure 34. They were graded in full length as “C” veneer. Narrower pieces of veneer of better grade could not be marked from them.

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Figure 36.--These are the same sheets of veneer shown in figure 34, and show the method of cutting back sheets of veneer in length to get shorter lengths of better grade veneer. A split in the sheet at the left was marked out of the upper portion of the sheet making this a short piece of “B” grade veneer. An open knot was marked out of the upper portion of the next sheet making a shorter piece of “B” veneer. The other portion of this sheet would be “C” grade but is marked “X” for residue because it is too short to be included in with veneer of this grade.

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Figure 37.--Green veneer tally form showing typical entries in appropriate columns.

32 FPL-025

PUBLICATION LISTS ISSUED BY THE

FOREST PRODUCTS LABORATORY

The following lists of publications deal with investigative projects of the Forest Products Laboratory or relate to special interest groups and are avail-able upon request:

Architects, Builders, Engineers, Growth, Structure, and and Retail Lumbermen Identification of Wood

Box, Crate, and Packaging Data Logging, Milling, and Utilization

Chemistry of Wood

Drying of Wood

Fire Protection Laminates, and Wood-Base

Fungus and Insect Defects in

of Timber Products

Mechanical Properties of Timber

Structural Sandwich, Plastic

Components

Forest Products Thermal Properties of Wood

Furniture Manufacturers , Woodworkers, and Teachers of Woods hop Practice

Wood Fiber Products

Wood Finishing Subjects

Glue and Plywood Wood Preservation

Note: Since Forest Products Laboratory publications are so varied in subject matter, no single catalog of titles is issued. Instead, a listing is made for each area of Laboratory research. Twice a year, December 31 and June 30, a list is compiled showing new reports for the previous 6 months. This is the only item sent regularly to the Laboratory's mailing roster, and it serves to keep current the various subject matter listings. Names may be added to the mailing roster upon request.