Improved first knife for shield machine

The utility model discloses an improved first knife for a shield machine and belongs to the technical field of tools for shield machines. The improved first knife for the shield machine is a quick-wear part of the shield machine, and mainly performs the function of trenching and tearing. A tool structure capable of protecting a left large hard alloy block 1 and a right large hard alloy block 5 is provided, and is capable of being used in geological layers of sand and gravel. The tool structure comprises the left large hard alloy block 1 and the right large hard alloy block 5, a small hard alloy block 2 and a wearing layer 3, the improved first knife for the shield machine further comprises a first knife body composed of a left end body 6, a right end body 7 and an intermediate tool body 4, the left large hard alloy block 1 and the right large hard alloy block 5 are installed inside wide grooves at two sides of the first tool body in a brazing mode. The small hard alloy block 2 is installed inside a narrow gro