Impact drill

An impact drill comprising:

• a housing, said housing comprising an accommodation chamber and a through hole in communication between said accommodation chamber and the space outside said housing;
• a driving mechanism accommodated in said accommodation chamber, said driving mechanism comprising a transmission shaft positioned in said through hole for providing an torque and producing an impact force in the direction of rotation intermittently upon a resistance, said transmission shaft having a polygonal front segment extending out of said accommodation chamber;
• and
• a chuck unit, said chuck unit comprising a drill chuck and a first bearing, said drill chuck comprising a connection barrel defining therein a polygonal coupling hole press-fitted onto said polygonal front segment of said transmission shaft, and said first bearing mounted on said connection barrel and received in said through hole to secure said drill chuck to said housing.