/ Ê_ WOOD VENEER: LOG SELECTION, CUTTING, AND DRYING Forest Service U.S. Department of Agriculture Technical Bulletin No. 1577 Lutz, John F. 1977. Wood veneer : log selection, cutting, and drying. U.S. Dep. Agrie, Tech. Bull. No. 1577, p. 137 Summarizes current information on cutting and drying veneer from many species of wood. Particular emphasis is placed on wood and log characteristics that affect veneer production; tech- niques for peeling, slicing, and drying veneer; and species involved. KEYWORDS: Peeling, slicing, lathe, slicer, veneer quality, wood species, plywood, decorative panels, containers, thickness, physical properties, mechanical properties, grades. Oxford No. 832.20 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. Stock No. 001-O0O-03723-4. WOOD VENEER: LOG SELECTION, CUTTING, AND DRYING by John F. Lutz, Technologist, Forest Products Laboratory, Forest Service, U.S. Department of Agriculture The Laboratory is maintained at Madison, Wis. in cooperation with the University of Wisconsin. Forest Service Technical Bulletin No. 1577 U.S. Department of Agriculture January 1978 PREFACE The broad spectrum of veneer cutting and Curtis Peters, Harry Panzer, Joe Clark, and handling for a multitude of uses obviously cov- John McMillen stand out. ers a wide range of operations by many special- Other members of the Forest Service have ists, and involves hard-learned secrets. No one been particularly helpful with information on individual can be an expert in all areas—yet wood species, especially John Putnam and those his efforts must be in line with those of others involved with surveys of the forest resources. in research and industry. In these days of From representatives of the wood industry material shortages and pressure on energy have come advice, assistance, and encourage- sources, it seems doubly important to summa- ment. The contributors are legion, with partic- rize some of the principles and coordinate the ular help from Tom Batey of the American terminology. Plywood Association and Bill Groah of Hard- This bulletin is a view of the art of veneer wood Plywood Manufacturing Association on manufacture as seen by a specialist who spent many phases. the last 25 years in research and industry con- In preparing this bulletin, the author relied tacts. It represents an attempt to tie together heavily on three research publications he had the experiences of many for the benefit of all. written earlier. These three were published as Contributions to this web of information U.S. Department of Agriculture Forest Service have come from literally hundreds of people Research Papers, by the Forest Products throughout the United States. The references Laboratory. These were: listed here represent noteworthy contributions, ''Wood and Log Characteristics Affecting but only a few of them. Harder to document Veneer Production,'' by John F. Lutz, USDA are the thoughts and philosophies that have Forest Service Research Paper FPL 150, 1971. been shared with the author over the last quar- "Veneer Species That Grow in the United ter century. States,'' by John F. Lutz, USDA Forest Service Outstanding among these have been the con- Research Paper FPL 167,1972. tributions of other members of the Forest "Techniques for Peeling, Slicing, and Dry- Products Laboratory staff. The research efforts ing Veneer," by John F. Lutz, USDA Forest and considered judgment of H. 0. Fleischer, Service Research Paper FPL 228, 1974. Use of trade, firm, or corporation names in this publication is for the infor- mation and convenience of the reader. Such use does not constitute an official endorsement or approval of any product or service by the U.S. Department of Agriculture to the exclusion of others that may be suitable. 11 CONTENTS Page Introduction Wood and log characteristics affecting veneer production 1 Veneer quality as related to end uses ^ Hardwoods or softwoods for veneer 2 Physical properties of wood ^ Mechanical properties of wood -'■^ Properties of veneer logs ^^ Veneer from wood species that grow in the United States 21 Techniques for peeling, slicing, and drying veneer 29 Log storage ^^ Bark removal ^^ Sawing into bolts or flitches ^^ Conditioning wood prior to cutting veneer 34 Veneer cutting equipment 45 Knife and pressure bar on lathe and slicer ^^ Conveying and clipping veneer ^^ Veneer drying '^^ Quality control '^^ Veneer yields and volume needed for a plant 87 Veneer yields (rotary cutting) 87 Veneer yields (sliced) 87 Volume of timber needed to set up a veneer plant 88 Literature cited 89 Appendix I—Nomenclature of wood species and veneer 91 Appendix II—Physical properties of U.S. woods for veneer 95 Appendix III—Mechanical properties of U.S. woods for veneer Ill Appendix IV—Some processing variables of U.S. woods for veneer 116 Appendix V—Effects of log storage and processing on veneer characteristics 121 Appendix VI—Appearance and suitability of individual U.S. species for various uses of veneer 125 Glossary 133 Index 135 Requests for copies of illustrations contained in this publication should he directed to the Forest Products Laboratory y U.S. Department of Agriculture, Forest Service, P.O. Box 5130, Madison, Wis. 53705. iii WOOD VENEER: LOG SELECTION, CUTTING, AND DRYING INTRODUCTION The wood veneer industry uses over a thou- for veneer. Other U.S. species received closer sand different wood species to make products looks for this product, and species from other as diversified as rotary-cut box shook VL inch countries are being imported into the country (6.35 mm) thick to sliced decorative face in an increasing swell of species, qualities, and veneer Vioo inch (0.25 mm) thick. In the United quantities. States, the major veneer uses are for structural All of this has required more information— and industrial plywood components % to 1 inch information that has been pieced together (9.25 to 25.40 mm) thick and decorative wall painstakingly. Material on individual species is panels and furniture parts ?l6 to 1 inch (4.76 compiled for the benefit of the reader in the to 25.40 mm) thick. tables of the Appendix. But, whenever possible, With such a wide array of raw materials and the text of this bulletin tries to present the final end uses, the field may at first seem overly generalized approach, and for native U.S. complex. In part, this may be due to the scar- species. city of written information summarizing the Common names of wood species are generally technical aspects of wood veneer manufacture. given in this publication. But experienced users This bulletin describes the basic information are well aware of the pitfalls of common names. known about the processes used in manufacture Therefore, the corresponding official name of of wood veneer. Wherever possible, the log the tree from which the wood comes is shown selection, log heating, veneer cutting, and dry- in Appendix I, along with the specific botanical ing processes are generalized and described as name. a continuum. To be sure, many individual proc- essing problems are related to specific wood The information contained herein comes species. However, whenever possible the under- from Forest Products Laboratory publications, lying cause is described and a generalized ap- from other research organizations, and from proach to the problem is suggested. contacts with the veneer and plywood industry. Still, it is impossible to avoid some effects of The bulletin is written primarily for people individual species. In the past, when only a responsible for some part of the veneer manu- comparatively few species were used for facturing process. It may also be of interest to veneer, this was not a great problem. It began others, including those growing trees for use to increase, however, as the favored species as veneer, for log buyers, users of veneer, and could not continue to meet increased demands wood technology students. WOOD AND LOG CHARACTERISTICS AFFECTING VENEER PRODUCTION A successful veneer operation depends on veneer, the logs must have the appropriate three items: A supply of suitable logs, good wood and log characteristics. The desired wood processing techniques, and a good sales organi- and log characteristics, in turn, depend on the zation. Most important is an adequate supply end uses of the veneer. of suitable logs. Then to produce suitable VENEER QUALITY AS RELATED TO END USES In this bulletin, veneer is defined as wood the stiffest and strongest and group 5 the least cut Vioo to % inch (0.26 to 6.35 mm) in thick- stiff and strong. Properties that are considered ness by a knife, whether by rotary or slicing include bending (modulus of elasticity and methods. Three characteristics of veneer that modulus of rupture), compression parallel and are desirable for all end uses are uniformity of perpendicular to the grain, and shear. thickness, minimum surface roughness, and Classification of species of veneer specified minimum buckle. For decorative face veneer, in Product Standard PS 51-71 for Hardwood control of figure, color, and depth of checks and Decorative Plywood is given in table 3. As into the veneer are important. Other veneer indicated in the table, the classification is based containing natural defects, such as knots, knot- on specific gravity. Face veneer for decorative holes, splits, and discoloration, can be used as plywood is graded primarily by appearance. inner plies in many products and as faces of Species for use in wirebound boxes as speci- some products like sheathing and container ply- fied in Federal Specification PPP-B-585b are wood. listed in table 4. The four groups are based on Four broad categories and typical end uses specific gravity and other properties of impor- of veneer are given in table 1, as well as some tance in containers such as strength as a beam, wood qualities as they relate to uses of veneer.