Hardness measuring instrument with protection function

The utility model relates to the technical field of hardness measuring instruments, and discloses a hardness measuring instrument with a protection function, which comprises an instrument body, an operation box connected to the upper end of the instrument body and a measuring hole positioned on a cover plate of the operation box, the two sliding grooves are located in the two sides of the measuring hole and are symmetrically arranged, sliding blocks are slidably connected into the sliding grooves, two symmetrically-arranged arc-shaped semi-rings are connected to the upper surface of the operation box, connecting rods are fixedly connected to one ends of the arc-shaped semi-rings, and the lower surfaces of the connecting rods are fixedly connected with the tops of the sliding blocks. The two arc-shaped semi-rings are slidably connected to the two sides of the measuring hole, so that a user can adjust the distance between the two arc-shaped semi-rings according to the diameter of the measuring pressure head to