THE SAWMILL 



121 



Opening' of knee on 



carriage. 



Allis-Chalmers Co., 



Milwaukee, Wis. 



I! 



The dogs are hooks or clamps or teeth, meant to grasp the log. They are fastened either inside 

 or outside of the l\nee. 



Two tooth bars, playing inside a hollow knee and pressed by a powerful lever, replace the original 

 dogs in modern mills. 



"Underdogs" are used in quarter sawing. 



The number of head blocks, knees, and 

 dogs is variable. The minimum is two of each. 



(d) The set works consist of: — 



1. The set beam, a shaft running under- 

 neath the carriage from head block 

 to head block, with a pinion at each 

 head block. This pinion corresponds 

 with a rack forming the tongue or 

 basis of each knee. 



2. The index disc and ratchet. 



3. The set lever, handled either by the 

 sawyer, in small sawmills, or by the 

 setter, in larger mills. 



The set works are usually double acting, 

 so that the knees advance with the to and fro motion of the set lever. 



In addition, each knee can be moved individually on its rack by the so-called taper movement. 



Rope driven and steam driven setworks are largely used in modern mills. 



The knees, before a new log is loaded, are receded either by a spring device or, on the gig motion 

 of the carriage, by a friction device. 



The brake wheel on the setshaft acts as a buffer when logs are loaded on the car. 



(e) The wheels. The wheels are attached either to the carriage or to the floor. The near wheels 

 are flat on the tire and the far wheels, called guide wheels, are grooved on the tire. 



In single cutting band mills an automatic off-set is required to prevent the face of the log from 

 striking the saw on the gig motion. 



The steel rails are invariably placed on stringers. 



II. Driving machinery. The to and fro trips of the carriage are known as feeding and gigging trips. 



(a) In small mills the motive power is derived from the saw arbor by. - 



1. Rack and pinion device. 



2. Chain, rope, or cable running over one or several sheave drums. 



The speed is regulated either by so-called cone pulleys (two, three, or four on the same shaft) or 

 by a paper friction device. 



The so-called Reamy Disc Friction allows of a variable speed. 



The usal feed, with the cone pulley, is from Vi inch to 3 inches per revolution of saw. 



(b) In large mills (unless the logs are long) the piston of a steam cylinder pushes the carriage to 

 and fro (so-called shotgun feed). In that case the carriage usually runs on three rails (center guide rail). 



(C) ADDITIONAL PARTS OF HIGH GRADE SAWMILLS: 



I. "The log haul-up" (elevator) consists of a flanged foot wheel and an inclined trough, on the bottom 

 of which runs a strong endless chain driven by sprocket wheels. The chain has steps (called welds) at 

 intervals of about 6 feet. 



The haul up is driven by a separate engine or from the main shaft by double gear wheels. It con- 

 sumes a great deal of power. 



16 



