Structural Flakeboards and Composites 



2921 



Figure 24-3. — Transverse micrographs of 0.020-inch-thick flakes illustrating zones of 

 weakness from micro-checks formed when flakes were cut (top), and surface rough- 

 ness attributable to cut vessels (bottom left). Checks may be further fractured during 

 hot pressing (bottom right). (Photos from files of W. A. Cote, see text footnote^.) 



Length, width, and thickness of flakes. — The effects of flake dimensions 

 on flakeboard properties are discussed and iflustrated in section 24-9. In general, 

 the 3-inch-long, 0.015-inch-thick flakes illustrated in figure 18-264 are near 

 optimum for face flakes of sheathing panels in thickness of 3/4-inch or less. Core 

 flakes can be thicker (perhaps 0.025 inch) and may be shorter (perhaps 1.5 

 inches long). 



Selection of flaking machinery. — Machines to manufacture flakes, their 

 power requirements, and their production capacities are described in section 1 8- 

 25 and by figures 18-264 through 18-274C. Thin veneer, precisely cut from wet 

 heated wood to prescribed length and width (fig. 18-264) approximates the 

 optimum flake, with minimal crossgrain and precisely controlled thickness. Of 

 the commercial machines available, the shaping-lathe headrig — or the roundup 

 lathe that operates on the same principle (figs. 18-104ABCD and 18-252) — 

 probably offers the best feed control and hence best control of flake thickness 

 and avoidance of cross grain. 



^Furuno, T., W. A. Cote, and C.-Y. Hse. 1981. Observation of microscopic factors affecting 

 strength and dimensional properties of hardwood flakeboard. Study FS-SO-320I-29. South. For. 

 Exp. Stn., U.S. Dep. Agric, For. Serv., Alexandria, La. (Manuscript in preparation.) 



