OTHER MACHINES 



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mitted in the sewing machine. Notice we have a treadle 

 which transfers power to the drive wheel. If we measure 

 the diameter of this wheel, and the diameter of the pulley 

 over which the belt passes, we can easily determine 

 how many revolutions of the pulley will be pro- 

 duced by one revolution of the drive wheel, then 

 by carefully turning the pulley one complete revo- 

 lution, we can find how many stitches the machine 

 takes in each complete revolution. This is only 

 one of the problems which can be 

 worked out in connection with a 

 sewing machine. 



Other machines. A number 

 of other mechanical principles are 

 found in many machines used in 

 the home. Among them are the inclined plane, the wedge, 

 the screw, and the pulley. We have all used the inclined 

 plane in rolling heavy objects like the barrel up a grade. And 

 we have used the wedge, which is really two inclined planes 



B 



Observe how the screw is in reality 

 a spirally inclined plane. Ex- 

 plain diagram. 



Illustrating the use of the screw. 



put side by side, points together, in the ax or hatchet. The 

 common wedge when driven into the wood, forces it apart. 

 The screw is nothing more or less than a long inclined 



