FOREST UTILIZATION 71 



The best makes are the Atkins and Disston 

 saws. 

 (h) The double circular saw. 



For big logs and high speed a double circular saw 

 must be used. 



The width of the widest board which a single cir- 

 cular saw may cut equals radius minus three 

 / inches. Hence much valuable material is wasted 

 in the common circular saw mill sawing heavy 

 logs. 



The double circular saw shows an under or lower 

 saw of 56 inches or 60 inches and an upper saw 

 of 30 inches or 36 inches diameter. The top saw 

 should have a reversed motion (so as not to 

 throw sawdust into the lower saw), an arrange- 

 ment which it is difficult to secure. 



A hanger top saw can be added readily to any sin- 

 gle saw. Both saws should have the same speed 

 at rim. 



The top saw should' remain inactive so as not to 

 use up power when small logs are sawn. 



Inserted teeth are not used at the double mills. 



The advantages of the double saw mill are: 



1. Less chattering and truer cut than would 



be possible for one big saw. 



2. Thinner kerf. 



3. Faster feed. 



4. Cess expense for saws. 



5. Less repairs. ' 



(i) Remarks relative to ''putting up" portable circular 

 saw mills: 



The minimum yard required is 50,000 board feet. 



The expense of tearing down and putting up again 

 is about $50. 



For foundation timbers, place two pieces 8 x 10 

 inches x 11 feet long on either side of the saw 

 pit (3 feet deep) and underneath the "husk." One 

 piece 4x6 inches x yYz feet long is saddled into 

 the two big pieces, spanning the saw pit under- 

 neath the far rail of the track. 



Construct the carriage track absolutely straight 

 and level on the track ties (16 to 25 in number) 

 and on the saw pit span. 



Place carriage with rack shaft, feed and gig works 

 in place and fasten the track byi cleats and nails 

 solidly to the foundation timbers. Then place the 

 husk on them at a distance of about 6 inches 

 from the track, putting wedge blocks between the 



