438 APPLIED SCIENCE 



In using it, accidents often occur in unexpected ways. A 

 change in the grain of the wood, the striking of a knot, or 

 too heavy a cut may hurl the piece from the machine and 

 throw the workman's hands into the knives. Yet it may 

 be simply and easily guarded, so as to render it safer than 

 many other wood-working machines. 



A workman should always try a jointer before using it, 

 for the knives may be set to take too heavy a cut. In such 

 a case the piece would be hurled back on him. In using a 

 jointer, the operator should not allow his hands to rest on 

 the portion of the stock which is over the knives if it is 

 possible to avoid doing so. 



Questions 



1. Why is machine-work more economical than hand-work? 



2. Name the different kinds of power saws. How do they differ? 



3. Describe the action of a band-saw. 



4. What is a wood-planer? 



5. What is a wood-jointer? 



6. Trace the power from the main shaft to the parts of a turn- 

 ing lathe. 



7. Describe a wood-turning lathe. 



8. Describe briefly the following power machines: the shaper, 

 boring mill, mortising machine, and tenon machine. 



9. Why is it possible to run wood-working machines faster 

 than metal-working machines? 



10. Why must great care be exercised in running wood-vorking 

 machines? 



11. Name some of the guards used on machines. 



