Solid Wood Products 2585 



There has been considerable controversy over the relative quality of red 

 (heartwood) and white (sapwood) hickory. Specifications frequently call for all 

 white wood, causing much good red hickory to be left in the woods or scrapped 

 at the mill. Tests by the U.S. Department of Agriculture, Forest Service (1936) 

 showed conclusively that weight-for-weight, red, white, and mixed red and 

 white sound hickory all have the same strength, toughness, and resistance to 

 shock. 



Lehman (1958) explained the basis of discrimination against red hickory. He 

 noted that red hickory is the heartwood and is in the inner part of the tree. On 

 trees from virgin forests this wood may be 100 or more years old and was formed 

 under forest conditions which produced slow growth. Slow growth in hickory 

 produces low-density, lower-strength wood (fig. 7-7). As the virgin forests were 

 cut, and when many of these hickory trees were released by partial cutting, the 

 growth rate increased and the white sapwood in the outer portions was denser 

 and stronger than their red heartwood. 



Now that much of the virgin old-growth hickory has been cut and the hickory 

 in managed forests is growing at a fairly rapid rate, the heartwood and sapwood 

 should not differ appreciably in density, and red hickory is generally as strong as 

 the white. True hickories, on the whole, shrink more, but tend to have greater 

 shock resistance than the pecan hickories (Lehman 1958). 



Paul (1947) observed that scrubby hickory trees from poor sites will not 

 supply much defect-free, fast-grown wood for high-class handle stock; more- 

 over, limby trees on poor sites produce cross-grain wood and display more bird 

 peck and insect damage than more thrifty trees grown on sites better suited to 

 hickory. He found that the bark of hickory trees offered clues to wood quality. 

 On slowly growing trees, there are few of the light-colored streaks at the bottom 

 of bark furrows which are evidence of rapid diameter growth. On shagbark 

 hickory instead of light streaks between ridges, fast growing trees shed more 

 bark than those which are stagnating. 



No non-destructive test has been devised that accurately predicts impact 

 resistance of hickory. Such parameters as static or dynamic modulus of elastic- 

 ity, or velocity of sound in longitudinal transit, seem not strongly correlated with 

 impact strength. Old-time craftsmen, however, found that stiff and resilient 

 handle stock, when dropped endwise onto a concrete floor, produces a clear 

 ringing sound. A dull thudding sound, or even a low-pitched tone, indicates it is 

 likely low in stiffness and probably will not straighten readily after being bent 

 under load (Heck 1949). Paul (1947) proposed that the best grades of striking 

 tool handles should have less than 17 rings per inch or weigh at least 55 pounds 

 per cubic foot at 12 percent moisture content. Crossgrain in handles, resuhing 

 from sawing at an angle to the grain, is the major cause of handle breakage. 



REQUIREMENTS FOR HICKORY BOLTS 



Grades for hickory bolts (fig. 22-1 1) representative of those used by midwest- 

 ern and southern handle companies are given in table 22-7. 



