A lock device includes a housing with a center through hole and a core that matches the center through hole. There is a center through hole engagement groove in the wall of the center through hole and there is a core engagement groove opposite this center through hole engagement groove. The lock includes a fitting ring and elastic part. The fitting ring and elastic part are between the center through hole engagement groove and the core engagement groove, within the core engagement groove. The advantages of the aforementioned lock are that assembly is convenient and use is not easily affected by assembly.