3282 



Chapter 27 



_ ^ ,,^^ , Bd ft lumber yield - Bd ft log scale .^^ ^nx 



Percent overrun = (100 ) ^ ^ (27-39) 



Bd ft log scale 



Overrun is greatly influenced by width and thickness of the product, accuracy of 

 manufacture, thickness of saw kerfs, and ability of the sawyers and edgermen. 

 Log diameter, log length, and the log scale used can also affect overrun. For 

 example, when 432 yellow-poplar logs were sawn at 34 circular mills scattered 

 throughout the Tennessee River watershed, overrun averaged 19 feet per log by 

 the Doyle rule and 2 feet per log by the Intemtional V4-inch rule (table 27-106). 

 With the Doyle rule, board-foot overrun increased with increasing log diameter, 

 especially between 5 and 15 inches dib, and with increasing log length from 8 to 

 16 feet. With the International rule, log diameter but not log length was signifi- 

 cantly related to board-foot overrun. The International rule gave a close estimate 

 of lumber tally for logs 5 to 14 inches in diameter. 



In another study of yellow-poplar, two bandmills sawings factory grade logs 

 produced an overrun of 6.8 percent by the International rule and 16.8 percent by 

 the Scribner Decimal C rule (table 27-107). There was no clear correlation 

 between overrun and log grade, but usually smaller logs showed a higher percent 

 overrun than larger logs. The relationship of log diameter to percent overrun is 

 shown in figure 27-9. 



40 1-4^ 



LOG DIAMETER (INCHES) 



Figure 27-9.— Relationship of log diameter (inside bark at small end) to percent overrun 

 in second-growth factory-grade yellow-poplar logs sawed in bandmills. (Drawing 

 after Campbell 1959.) 



Data on hickory (table 27-108) and hard maple (table 27-109) show similar 

 trends: percent overrun is greatest with the Doyle rule, lowest with the Interna- 

 tional rule, and intermediate with the Scribner rule. 



Another factor influencing overrun is type of sawing. Huyler (1974) found 

 that live-sawing factory grade 3 northern red oak resulted in a 7.3 percent 

 overrun based on the Scribner Decimal C log rule, compared to only 2.0 percent 

 when grade-sawing (table 27-110). The greater overrun from live-sawing was 



