Why are there different types of saw?

Different saws - are of many shapes and sizes, according to the special purposes for which they are to be used and the materials they are meant to cut. Most are designed to cut through wood but others have the particular qualities needed for cutting metals and stones. 
  There are two types of large hand saw. Both have steel blades with wooden handles but the teeth are shaped differently to fit the job they have to do. One is a cross cut saw for cutting across the grain of the wood. The leading edges of the teeth slope backward and are also bevelled or angled transversely. In other words they are cut away at the edges to give an oblique angle like the edge of a chisel thus producing a sharp pointed profile or shape designed to avoid splintering the wood. 
  The second type is the rip or tenon saw which is used for cutting along the grain of the wood. This has a smaller blade, strengthened by a steel strip along the top edge and smaller teeth. It is used as the name suggests in cutting tenon or slotted joints. 
  Smaller hand saws like the fretsaw, are used for cutting intricate shapes. These have a narrow blade stretched across an open frame. The hacksaw which is used for cutting metal by hand also has an open frame, but its blade is deeper and more closely toothed. 
       Machine saws are of three types:
1. A larger and stronger hacksaw operated by an electric motor through a crank and connecting rod.
2. A circular saw which has a rotating disc-shaped blade with teeth on the circumference.
3. A bandsaw which has a blade formed like an endless flexible band and tightly stretched over pulleys. 
  The bandsaw which has fine teeth along one edge operates at a higher speed than the circular saw. It can cut round curves of quite small radius because the blade is so narrow. 
  For stone-cutting in quarrying there are swinging gang saws with teeth like chisels and flat bladed circular saws which are either fed with a mixture of hard sand and water or fitted with rims of a hard abrasive substance called carborundum.
  The hand held power saw driven by an electric or petrol driven engine is used for felling trees and cutting logs. This is also known as a chain saw because it is much like a bicycle chain equipped with saw teeth. 

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