18 



HARDWOOD RECORD 



August 25, 1921 



The Manufacture and Seasoning of Oak 



By David G. White, Forest Examiner, U. S. Forest Service 



Timber From Which Logs Were Obtained for Mil 

 Study 



TIk' ailujitation of oak or any other 

 wood to tlie uses to which it is best suit- 

 ed, is largely dependent upon proper man- 

 f acture and conditioning. This article 

 discusses a number of factors involved 

 in the manufacture of oak which affect 

 the cost of production and the selling 

 price of the material, and give data on 

 the [iroper seasoning or conditioning of 

 the wood to reduce loss through depre- 

 ciation to a minimum. Such considera- 

 tions are of importance to both manufac- 

 turer and consumer. 



Factors affecting the efficiency of the 

 operation and the proportions of the va- 

 rious grades obtainable are of chief in- 

 terest to a manufacturer when convert- 

 ing logs into lumber. The efficiency is 

 indicated to a large extent by the rate 

 of production, percentage of waste and 

 care and judgment in sawing for quality. 

 Sawing for quality, or the obtaining of 

 the largest percentages of the highest 

 grades with a minimum of waste, is, huw 

 ever, largely dependent upon the size ami 

 quality of the logs. 



Many variations may be expected in 

 manufacture, depending upon the size 

 and type of sawmill, location and qual- 

 ity of timber, and like factors. In order 

 to obtain data on the manufacture of oak which might be said to 

 be representative, a mill-scale study was made by the Forest Prod- 

 ucts Laboratory at a typical hardwood band sawmill at Proctor, 

 Ark., in co-operation with George C. Brown & Co. and the Na- 

 tional Hardwood Lumber Association. The timber cut represents 

 the timberlands of the delta country of the lower Mississippi 

 Valley, which form the last large reservoir of hardwoods in the 

 United States. 



Stump ago and Logging 



Topography and climate play an important part in determining 

 the method of logging, and these factors, together with the method, 

 affect the cost. 



Stumpage and logging costs are usually obtained in terms of 

 log scale, and vary with size and quality of the trees, type of coun- 

 try, distance from mill and market, and like factors. The log scale 

 of any log seldom checks with the net lumber tally sawed out of 

 it, and the difference is overrun or underrun, as the case may be. 

 This overrun or underrun affects the cost per thousand feet net 

 lumber tally, which equals the cost per thousand log scale multi- 

 plied by the net yield log scale, and the result divided by the yield 

 not IuiiiIkm' tally of the same logs. 



Ovemm and Underrun 



During the millscalc study the red and wliitc oak logs were 

 scaled according to the Doyle rule. The difference between the 

 log scale and the net lumber tally, divided by the log scale, gives 

 the percentage by which the net lumber tally overruns or underruns 

 the log scale. The percentages of overrun or underrun for different 

 diameter classes and groups of logs for both red and white oak 

 are shown in tables 1 and 2. The differences between the full and 

 net log scale and between the full and net overrun or underrun are 

 the result of allowances which were made by the scaler for defects. 



The Doyle scale for any size log is predicated upon the following 



mathematical formula: 



[^Y 



X L 



Scale 



111 which D equals the diameter in inches 

 and L equals the length in feet. The 

 diameter in practice is usually taken at 

 the small end of the log inside the bark, 

 although "instructions given in Scrib- 

 ner's Log Book are to measure the log at 

 the middle."* This rule gives too small 

 a scale for small logs and too large a scale 

 fur large logs, as is shown in table 1; 

 i. e., the ratio of the log scale to the net 

 lumber tally steadily decreases as the 

 size of the log increases. 



On the logs manufacture<l during this 

 study the overrun changed to underrun 

 at a diameter of 23 inches for white oak 

 and at 29 inches for red oak. This varia- 

 tion was largely the result of the differ- 

 ent sawing methods used for the two 

 woods; for example, practically all good 

 white oak logs 20 inches or larger in 

 diameter were sawed to obtain the maxi- 

 mum amount of quarter-sawed boards, 

 but the red oak logs were not. Quarter- 

 sawing produces more waste than plain- 

 sawing. 



Methods of sawing, size and quality 

 are reflected in the overrun and underrun for the various groups of 

 red and white oak logs shown in table 2; i. e., the ratio of the log 

 scale to the net lumber tally is larger for small, sound, or plain- 

 sawed logs than for either large, defective, or quarter-sawed logs, 

 respectively. 



Rate of Production 

 The rate of production varies with the diameter of the log, the 

 method of sawing, time consumed in sawing for quality, ratio of 

 nominal to actual sizes, proportion of sizes, and like factors. The 

 red and white oak logs sawed during the study were cut by a sin- 

 gle-band saw with a kerf of 9/64 inch full. Approximately 91 per 

 cent of the product consisted of 1, 1% and 1%-inch lumber, 4^ per 

 cent of 2 and 3-inch stock, and 4% per cent of cross-ties and small 

 timbers. The sawing instructions were: 



1" plaiii-sawed red oak cut 5/32" full 



1" plain-sawed white oak cut 1/8 " full 



1" quarter-sawed red oak cut 1/4 " full 



]" quarter-sawed white oak cut 5/32" full 



5/4" and 6/4" plain-sawed red and white oak cut 1/8 " full 



5/4" and 6/4" quarter-sawed red and white oak cut 5/32" full 



8/4" plain-sawed red and white oak cut 1/8 " full 



Timbers .' cut 1/8 " full 



Tlie number of seconds required to saw logs of different diam- 

 eters is shown in titble 1. Time lost in changing saws, etc., was 

 jirorated against the various logs. Logs less than 16 feet 2 inches 

 in length were computed on the basis of 16 feet 2 inches for accu- 

 r;icy in comparing data. The time of sawing was then plotted 

 against yield net lumber tally and a curve drawn from which the 

 data in table 1 are taken. The time required for sawing the aver- 

 age log for the various groups is shown in table 2. 



The rate of production per hour shown in tables 1 and 2 was 

 obtained by dividing the yield net lumber tally by the number of 

 seconds required to saw the log, and multiplying the result by 

 •(Mnis, H. S., Forest Mensuration, page 40, 1912. 



