Occurrence of Spiral Grain in Poles 



A third study, made in 1952, was concerned with the frequency of occurrence of spiral 

 grain in poles. Poles totaling 800, either green or air seasoned 1 year, were examined in four 

 pole yards of the cooperators. These yards were located at Spokane and Newport, Washington, 

 and at Priest River and Sandpoint, Idaho. One hundred poles were examined during each of two 

 visits at the individual yards in order to obtain a representative production sample. The direc- 

 tion and degree of spiral grain were measured at the top, middle, and butt surfaces and the 

 measurements for each pole were averaged. 



Of the 800 poles examined, only 1 percent (7 poles) had a slope of grain of 1:10 or more 

 severe (table 2). Six and one -half percent of the poles (53 in number) had a slope of grain be- 

 tween 1:11 and 1:20. Forty -eight percent of the poles were practically straight grained, i.e., 

 1:201 or more. 



Table 2. - -Spiral -grained poles classified by pole yard and spiral ratio classes 



Spiral ratio : Yard 



class : A : B : C : D : All yards 



_______ Number — - Number Percent 



1 



1- 10 



3 



1 



1 



2 



7 



1.0 



1 



11- 20 



15 



9 



13 



16 



53 



6.5 



1 



21- 50 



53 



32 



■ 28 



38 



151 



19.0 



1 



51-100 



34 



32 



30 



19 



115 



14.0 



1 



101-150 



14 



26 



10 



10 



60 



7.5 



1 



151-200 



8 



4 



10 



11 



33 



4.0 



1 



201+^ 



75 



96 



108 



104 



381 



48.0 





Total 



200 



200 



200 



200 



800 



100.0 



Poles in this class are practically straight grained. 



Poles with spiral grain to the left occurred with greater frequency than poles with a slope 

 of grain to the right (table 3). Sixty -six percent of the poles examined had left-spiraled grain 

 as compared with 34 percent that had right -spiraled grain. The left-spiraled grain was even 

 more common where the spiraling was severe. All poles with a slope of grain of 1:10 or more 

 severe had left spiral, and 88 percent of the poles having a slope of grain of 1:20 or more severe 

 were left spiraled. 



Spiral grain had no apparent relation to pole circumference; there was no significant dif- 

 ference between pole groups of classes 1 to 4 and 5 to 7. ^ 



Variation in the slope of grain along the pole's length was common; maximum divergence 

 from the longitudinal occurred most frequently near the top of the pole (table 4) . Some variation 

 in the slope of grain was observed in 378 out of 400 poles for which these data were recorded. 

 The variation was usually relatively small, but spiral ratios as dissimilar as 1:720 and 1:20 

 were observed in a single pole. 



Pole classes are based on circumference at the groundline and top; the lower the number 

 the greater the circumference. 



5 



