Electric hammer drill

A hammer drill comprising:

• a housing;
• a motor disposed in said housing;
• a trigger mounted in said housing and connected between said motor and a battery pack adapted to be inserted into said housing;
• a gearing coupled to an axle of said motor;
• a shift rod having an upper end connected to a swivel cap, wherein a circumference of said swivel cap is rotatably embedded in an upper edge of said housing, said shift rod further having a lower vertical flat surface and a lower cylindrical surface so that said lower vertical flat surface will be spaced from a first end of a spindle when said swivel cap is at a predetermined position and said lower cylindrical surface will be in contact with said first end of said spindle when said swivel cap is rotated through an angle of 180 degrees;
• a chuck fixedly connected to a second end of said spindle outside said housing;
• an inner serrated collar rigidly mounted in said housing;
• an outer serrated collar connected with said spindle and disposed against said inner serrated collar wherein teeth members of said inner and outer serrated collars are opposed to each other;
• a dust proof packing arranged between said chuck and said outer serrated collar thereby preventing dust from entering said housing;
• and
• a spring mounted between and in contact with said dust proof packing and said chuck.