A self-locking nut includes a main-nut body and a deformable-nut body. The main-nut body has a recess leading into an interior threaded bore forming x turns of an internal thread therein. The deformable-nut body has an outer flange and an interior threaded bore forming y turns of an internal thread therein. The outer flange of the deformable-nut body is fixed to the main-nut body such that a relief space is formed between the deformable-nut body and the recess. A ratio of x:y is about 2:1.

A self-locking nut includes a main-nut body and a deformable-nut body. The main-nut body has a recess leading into an interior threaded bore forming x turns of an internal thread therein. The deformable-nut body has an outer flange and an interior threaded bore forming y turns of an internal thread therein. The outer flange of the deformable-nut body is fixed to the main-nut body such that a relief space is formed between the deformable-nut body and the recess. A ratio of x:y is about 2:1.

A double nut is provided in which a flange nut and an insert nut are coupled. The flange nut has a longitudinal axis and has, in an end region facing the insert nut, a stop surface and a wall surface. The insert nut has a longitudinal axis and has at least one snap element in an end region facing the flange nut. The stop surface extends over the at least one snap element radially in the direction of the longitudinal axis of the flange nut. The flange nut has a guide surface in the end region facing the insert nut which is disposed closer to the longitudinal axis of the flange nut than the wall surface.

Provided is a nut that resists being loosened and is easy to be tightened. A nut 600 includes a nut main body 10 having a tapped hole 30 formed therein; an annular member 41 formed on the side of a top surface of the nut main body 10; and an outer frame member 45 formed on the side of an outer edge of the annular member 41. The annular member 41 includes a second end portion 42b in contact with a top surface 11 of the nut main body 10 and a first end portion 42a located opposite to the second end portion 42b. A top surface of the first end portion 42a is located above a top surface of the second end portion 42b. A first gap 40 is formed between the first end portion 42a and the top surface 11 of the nut main body 10. A second gap 49 is formed between a side surface of the annular member 41 and an inner wall 47 of the outer frame member 45. The top surface of the first end portion 42a of the annular member 41 is located above a top surface 46 of the outer frame member 45. The inner wall 47 of the outer frame member 45 is inclining while tapering in an upward direction.

A lock nut includes: a first nut having a tapered cavity; and a second nut including a base portion and a tapered lug boss arranged the base portion. The tapered lug boss can be coupled inside the tapered cavity. The first and second nuts are used in pair by self-locking. A straight slot is formed in the lug boss. Under the locking action of the first nut, the straight slot is deformed to further lock a bolt, or is discontinuously engaged with teeth of the bolt to increase an effective stress surface and locking performance of the second nut for locking the bolt. A convex reinforcing rib extends on a first surface of the first nut. An annular groove is formed in a second surface of the second nut. The convex reinforcing rib is coupled with the annular groove to enhance the strength and reliability of locking.

An object of the present invention is to provide an anti-loosening device that exhibits its anti-loosening effect by means of an eccentric fit between a protrusion 12 of a nut 10 and a recess 22 in a nut 20, wherein the inclination of the nut 20 relative to the nut 10 when they have been tightened is minimized. The outer peripheral surface of the protrusion 12 and the inner peripheral surface of the recess 22 are constructed in such a manner that, with the nuts screwed to a threaded shaft S and an eccentric fit established between the protrusion 12 of the nut 10 and the recess 22 in the nut 20, the tapered outer peripheral surface portion 12a of the protrusion 12 interferes with the tapered inner peripheral surface portion 22a of the recess 22 along part of the circumference while a gap is formed between the distal-end outer peripheral surface portion 12b of the protrusion 12 and the closer-to-bottom inner peripheral surface portion 22b of the recess 22 along the entire circumference.

A fastening system having a T-bolt, a nut, and a washer. The T-bolt includes a bolt head having a bolt head base portion and a bolt head collar portion. The nut includes a threaded opening for engaging corresponding threads of the T-bolt shaft. The washer includes a washer base portion, a washer collar portion, and an aperture extending through the washer base portion and the washer collar portion for slidably positioning the washer around the shaft of the T-bolt between the nut and the bolt head. When the fastening system is in an installed position, the bolt head base portion engages an outer surface of a first joining member, the washer base portion engages an outer surface of a second joining member, and the bolt head collar portion and the washer collar portion both extend at least partially into an opening formed by aligned slots of the joining members.