Chisel with double limit discs

A chisel (5) with double limit discs, comprising a holding seat (3) and a bit mounted on the holding seat (3), the bit comprising a head (7) and an extension (8) provided on the lower side of the head (7), the bottom of the head (7) having a head support surface (7.1), and the upper end surface of the holding seat (3) having a stress surface (3.4), wherein, a first limit disc (1) and a second limit disc (2) arranged up and down are mounted between the holding seat (3) and the head (7), the middle of the first limit disc (1) having a first mounting through hole (10), and the middle of the second limit disc (2) having a second mounting through hole (20), the second limit disc (2) being partially concaved or partially convexed with the first limit disc (1);

• the extension (8) passes through the first mounting through hole (10) and the second mounting through hole (20);
• wherein, the second limit disc (2) is partially concaved with the first limit disc (1);
• the lower side of the first limit disc (1) has a lower surface (1.5) and a positioning portion (1.4), the positioning portion (1.4) being an annular convex arranged on the lower edge of the first mounting through hole (10);
• the upper side of the second limit disc (2) has a force guide surface (2.1) and a guide portion (2.2), the guide portion (2.2) being an annular concave arranged along the upper edge of the second mounting through hole (20);
• the lower surface of the second limit disc (2) has an annular support surface (2.6);
• wherein, the upper surface (I.I) of the first limit disc (1) is in contact with the head support surface (7.1) of the chisel (5);
• the lower surface (1.5) of the first limit disc (1) is in contact with the force guide surface (2.1) of the second limit disc (2), and the support surface (2.6) of the second limit disc (2) is in contact with the stress surface (3.4) of the holding seat (3);
• wherein, the lower side of the second limit disc (2) is provided with a convex portion (2.7′) along the second mounting through hole (20), the upper end surface of the holding seat (3) has a concave support portion, the convex portion (2.7′) is matched embedded in the support portion, and there is a clearance between the convex portion (2.7′) and the support portion.