Solid Wood Products 2679 



Relative price 

 Product Measure (if ties have index of 100) 



Million board feet Index 



Headers 107.4 82 



Half-headers 79.4 81 



Wedges 25.4 132 



Crib blocks 31.3 64 



Ties 25.6 100 



Miscellaneous timbers 25.9 67 



Additionally 159 million lineal feet of props were sold in 1967; a thousand lineal 

 feet of props brought 72 percent of the sales price of a thousand board feet of 

 mine ties. 



Knutson (1970) found that most of the round and split prop timbers are 36 to 

 70 inches long; average length is about 53 inches, and average diameter about 6 

 inches. Other mine timbers measured about as follows: 



Product Thickness Width Length 



Inches Feet 



Wedges '/s-l 4 1 



Crib blocks 5 5 2-Vi 



Half-headers 2 8 l-'/a 



Headers 3 8 14 



Ties 5 7 6 



Miscellaneous 1 10 12 



Some coal companies use pressure-treated timbers — particularly ties; the deter- 

 mination of which products are to be treated depends on the expected life of the 

 mine. 



Mine-timber specifications. — Coal-mine operators require timbers suitable 

 for the intended use in the mine, manufactured to their standards, and structural- 

 ly sound. Timson (1978a) summarized (table 22-25 and fig. 22-62) minimum 

 characteristics of roundwood suitable for manufacturing sawn mine timbers and 

 round and split props. Roundwood for mine timber production can be cut from 

 hardwood logging residues. Timson (1978b) found that after a sawlog cut 44 

 percent of logging residue measuring at least 4 feet long and 4 inches in diameter 

 outside bark was suitable for mine timber production, i.e., 26 percent of the 

 limbwood and 58 percent of the bolewood residue. White oak, chestnut oak, 

 northern red oak, hickory, yellow-poplar, and red maple were among the species 

 studied. 



Species preference. — Knutson (1970) found that each mine operator has his 

 preference, but generally uses species available in the locality of his mine. 

 Regional usage is about as follows, for sawn timbers: 



Species Proportion of total 



Red oak sp 55 



Hickory 15 



Yellow-poplar, basswood, and cucumbertree 15 



Beech 6 



Miscellaneous hardwoods 4 



Pine and hemlock 5 



Round and split props are primarily oak, hickory, and beech. 



