Four-hole core drilling machine

A four-hole core drilling machine comprising:

• a body;
• a vertically reciprocating carriage vertically reciprocably mounted to the body;
• a motor coupled to one side surface of the carriage;
• a fixing plate coupled to one side of a lower portion of the carriage, to rotatably support a drive shaft of the motor,
• a pivoting plate fastened to the fixing plate under a condition that a pivot angle of the pivoting plate is changed;
• a drive sprocket coupled to the drive shaft, to be rotatable by the drive shaft;
• four driven sprockets rotatably mounted to the pivoting plate near corners of the pivoting plate, respectively;
• four driven shafts rotatably mounted to the pivoting plate while extending through the pivoting plate, the four driven shafts being coupled to the four driven sprockets, to be rotatable by the driven sprockets, respectively;
• a chain mounted around the drive sprocket and the four driven sprockets, to transmit rotation force of the drive sprocket to the four driven sprockets;
• and
• four core bits coupled to lower ends of the four driven shafts, respectively.