6i8 



Yearbook^ of Agriculture 1949 



pacity to withstand suddenly applied 

 loads. Tough woods, therefore, can 

 withstand repeated shocks or blows, 

 such as are given ax handles, wheel 

 spokes, and wagon tongues. Because 

 they are high in comparative tough- 

 ness, the following woods are used in 

 farm and home building when tough- 

 ness is desired: Ash, beech, yellow 

 birch, elm, hackberry, hickory, locust, 

 hard maple, oak, and walnut. Of those 

 woods, hickory is used most often if 

 toughness is the main requirement. 



NAILS, screws, and bolts for joining 

 his work are a primary concern of the 

 home woodworker, although a vari- 

 ety of timber connectors have been 

 developed. 



Because the strength of a unit de- 

 pends on the fastenings, they merit 

 careful consideration. The denser and 

 harder the wood, the greater is its in- 

 herent nail-holding power. This resist- 

 ance to withdrawal increases almost 

 directly with the diameter of the nail. 

 Thus, if the diameter of the nail is 

 doubled, the holding power is doubled, 

 providing the nail does not split the 

 wood when it is driven. Nails have 

 been treated in various ways in an 

 effort to increase their holding power. 

 Among such nails that are in common 

 use, the cement-coated nail has a 

 higher holding power than the com- 

 mon nail in well-seasoned wood, and 

 the barbed nail a lower value. 



The moisture content of the wood at 

 the time of nailing strongly affects the 

 holding power of nails driven into it. 

 The best guarantee of good joints and 

 high nail-holding power is to use well- 

 seasoned wood. Nails driven into wet 

 wood lose as much as three-fourths of 

 their full holding power when the wood 

 becomes dry, and such a practice can 

 result in the loosening of siding, barn 

 boards, fence pickets, and the like. If 

 one has to use unseasoned wood, it is 

 best to use barbed nails in it. 



The holding power of nails is greatly 

 reduced if the wood splits ; even a slight 

 amount of splitting results in a con- 

 siderable loss in holding power. The 



heavy, dense woods, such as maple, 

 oak, and hickory, split more in nailing 

 than do the lightweight woods, such as 

 basswood, spruce, and the true firs. 

 Woods of uneven texture, such as 

 southern yellow pine and Douglas-fir, 

 split more than do the uniform-tex- 

 tured woods, such as eastern white 

 pine, sugar pine, or ponderosa pine. 

 Splitting due to nailing can be reduced 

 by using smaller nails, but the number 

 of nails must be correspondingly in- 

 creased to obtain the same holding 

 power. Blunt-pointed nails have a 

 smaller tendency to split wood than do 

 sharp-pointed nails, but blunt-pointed 

 nails have lower holding power. The 

 danger of splitting can be reduced by 

 staggering the nails or by boring holes 

 for the blunt-pointed nails. 



THE SURFACE CHARACTERISTICS of 



the wood affect its appearance and its 

 strength and so should be considered 

 when wood is selected for specific uses. 



If maximum strength or fine appear- 

 ance is desired, the material should be 

 chosen from the select grades, from 

 which most knots, pitch pockets, and 

 the like are eliminated. The common 

 grades, which include those defects in 

 greater or lesser amounts depending 

 upon the wood, should be used if ap- 

 pearance or high strength is not of 

 primary importance or if knots or other 

 defects are desired for architectural 

 effects, as in knotty pine trim. 



A knot is the part of a branch or limb 

 that has become embedded in the body 

 of a tree and subsequently has been cut 

 through in the process of lumber man- 

 ufacture. There are various types of 

 knots, but the distinction that the 

 woodworker should know is the one be- 

 tween an encased knot and an inter- 

 grown knot. An encased knot is one 

 whose rings of annual growth are not 

 grown into those of the surrounding 

 wood. An intergrown knot is one whose 

 rings are completely intergrown with 

 those of the surrounding wood. Be- 

 cause the grain of knots is at a consid- 

 erable angle to the grain of the sur- 

 rounding wood, the knots in a flat-sawn 



