A lathe includes a main shaft, a moving shaft, a cutter mounted on the moving shaft, and a clamping assembly. The cutter is capable of telescopic translation relative the moving shaft. The clamping assembly includes a cylinder mounted on the cutter, an assembly member mounted on the cylinder, a moving member, and at least two clamping members. The cylinder defines an inner cavity, and a first air intake and a second air intake communicated to the inner cavity. The moving member is movably mounted in the inner cavity and partially received in the assembly member, and capable of telescopic translation relative the assembly member. The clamping members are movably mounted on the assembly member and engaged with the moving member. The clamping members are translatably urged by the moving member in a direction relative the axis defined by the assembly member.