Throw-in type drill rod drift diameter gauge and application method thereof

The invention provides a throw-in type drill rod drift diameter gauge and an application method thereof, and belongs to the field of oil exploration. The device comprises a center shaft and a sealingsleeve sleeving the center shaft, wherein a sealing space is formed between the inner wall of the sealing sleeve and the outer wall of the center shaft; liquid is fully filled in the sealing space; and when a force along the axial direction of the center shaft is applied to the sealing sleeve, the outer diameter of one part on the sealing sleeve can be enlarged. According to the device, the problem that an existing drift diameter gauge cannot detect a mud cake with a certain thickness and other similar adherent objects adhered to the wall surface of a diameter enlargement section of an inner cavity of a drill rod can be solved, the inner cavity of the drill rod is ensured to be clean and smooth to the utmost extent, and the risk of entering a well and being blocked is reduced; the device adopts modular designing a