2964 Chapter 24 



WHITE OAK (PERCENT) 



100 50 



50 100 



SWEETGUM (PERCENT) 



Figure 24-31. — Relationship of modulus of elasticity to proportion of white oak and 

 sweetgum lathe flakes in 1/2-inch flakeboard; all boards pressed to a density of 42 

 pounds/cu ft, ovendry-weight basis. (Drawing after Hse et al. 1975, from Price 1974.) 



Flake quality. — Price (1974) demonstrated the major dependence of MOE 

 on flake quality. Flakes cut on the shaping-lathe headrig (fig. 18-102 and 18- 

 274ABC) are of good industrial quality, though substantially less uniform in 

 thickness and width than veneer flakes (fig. 18-264). Price showed that lathe 

 flakes made boards of substantially lower MOE than did veneer flakes, and that 

 MOE values are correlated with proportions of the two flake types (fig. 24-32). 



Among major types of industrial flakers (drum, disk, shaping lathe, and ring) 

 evaluated by Price and Lehmann (1978), the shaping-lathe produced oak and 

 hickory flakes (fig. 18-274 be) that yielded boards with highest MOE (fig. 

 24-5). 



As noted in section 24-4, slope of grain in flakes reduces flake MOE signifi- 

 cantly, e.g., a 10-degree slope of grain can reduce flake MOE by 16 percent, and 

 a 20-degree slope by 33 percent. Incorporation of cross grain flakes in a panel 

 therefore lowers panel MOE. 



Flake length/thickness ratio. — Flakeboard MOE increases as the ratio of 

 flake length to thickness increases in face layers. The rate of increase is substan- 

 tial at ratios below 200, but slows at higher ratios. While flakes 6 inches long and 

 longer have been used experimentally, most existing flakeboard plants limit 



