The invention relates to augers generally, and more particularly to an auger having a first and a second interchangeable end portion wherein the first end portion is adapted to bore though soft ground material and the second end portion is adapted to bore though hard ground material. 
Augers are known and typically comprise a shaft with a boring head at one end.  The boring head is adapted to cut through and generally loosen ground material ahead of the shaft.  Spiral flighting is wound around the shaft for conveying the loosened ground material spoil from the boring head to the surface of the area being excavated.  There are different kinds of augers for excavating different kinds of ground materials.  One type of auger comprises a boring head and drilling elements (i.e. teeth or bits) adapted to bore through soft ground conditions such as dirt or clay.  An example of this type of auger is disclosed in U.S. Pat.  No.  5,476,149 (Rickards), which is hereby incorporated by reference.  Although the type of auger disclosed in this patent works well for excavating soft ground conditions, it is not well suited to grind and bore through hard ground conditions because its boring head and drilling elements are not designed to bore through rock and other hard ground conditions.  Further, even if the soft ground boring head were able to drill through rocky ground conditions, the auger may be damaged due to its lack of protection from the abrasive rocky spoils. 
Another type of auger comprises a boring head and drilling elements adapted to excavate hard ground conditions such as rock.  An example of this type of auger is disclosed in U.S. Pat.  No.  5,427,191 (Rickards), which is hereby incorporated by reference.  Although this type of auger works well for excavating rock, it is not well suited for excavating dirt because of the design of its boring head and drilling elements. 
As discussed above, some types of augers are designed to excavate dirt and other types of augers are designed to excavate rock.  The problem with having different augers dedicated to excavating different types of ground materials is that the user must purchase a different auger for excavating each different ground condition, which can be expensive for the user.  Further, it can be difficult to predict which type of ground condition (i.e. dirt or rock) is going to be encountered during an excavating operation, therefore, the user must carry all augers with him/her at all times which can be inefficient and burdensome for the user. 
There is therefore a need for a single auger having two interchangeable boring heads wherein the first boring head is adapted to bore through soft ground conditions such as dirt and the second boring head is adapted to bore through hard ground conditions such as rock.