458 APPLIED SCIENCE 



and a machine shear for cutting out circles and perforating 

 holes. 



Sheet-metal tools usually are more difficult to make than 

 other giades of tools, because those parts which stand out 

 or project must be hardened. The part of the tool that does 

 not require hardness is usually made of iron, while the work- 

 ing parts, which must be firm and hard, are made of composite 

 steel. 



Questions 



1. What is sheet-metal work? 



2. Explain the difference between the work of the copper- 

 smith and the sheet-metal worker. 



3. What are some of the metals used for sheet-metal work? 

 Why are these particular metals used? 



4. How are sheet metals obtained? 



6. Explain the processes by which copper is obtained. 



6. What are the physical properties of copper? 



7. What are the chemical properties of copper? 



8. Why has aluminum been used extensively in recent years? 



9. How is it obtained? What are its physical and chemical 

 properties? 



10. What is an alloy? Why are alloys used? Name some 

 alloys of aluminum. 



11. Explain why tin is not used more extensively. How is tin 

 plate made? 



12. Give the uses and the physical and chemical properties of 

 lead. 



13. Name some alloys of lead and give properties of each. 



14. Explain how zinc is obtained. Give the physical and chemi- 

 cal properties of zinc. 



15. For what is mercury used in the trades and industries? 

 Give physical and chemical properties. 



16. Name some of the physical and chemical properties of 

 platinum. 



17. Explain some of the properties and uses of antimony awl 

 bismuth. 



