A multi-material boss, configured for fastening of a fastener thereto, being a feature of a the cast part, comprising a boss cylinder, an augmenting cylinder, and a filler metal layer is provided. The boss cylinder is made of the same material as the die cast part having a first hardness, and has a first interior. The augmenting cylinder is made of an augmenting material having a second hardness, is fixedly secured in the first interior of the boss cylinder, and has a second interior defined by a second cylindrical shaped wall, a base rim, and a second opening. The second hardness is greater than the first hardness. The fastener is fastened to the multi-material boss via the second opening of the augmenting cylinder having the higher liquidus temperature and greater hardness.

A multi-material boss, configured for fastening of a fastener thereto, being a feature of a the cast part, comprising a boss cylinder, an augmenting cylinder, and a filler metal layer is provided. The boss cylinder is made of the same material as the die cast part having a first hardness, and has a first interior. The augmenting cylinder is made of an augmenting material having a second hardness, is fixedly secured in the first interior of the boss cylinder, and has a second interior defined by a second cylindrical shaped wall, a base rim, and a second opening. The second hardness is greater than the first hardness. The fastener is fastened to the multi-material boss via the second opening of the augmenting cylinder having the higher liquidus temperature and greater hardness.

There is provided a nut in which occurrence of galling is prevented. The nut in which a depth t of a counterbore hole is set to be greater than (D−d×cos θ)/tan θ, when a nominal diameter is D, an average value of a maximum outer diameter and a minimum outer diameter taking into account a tolerance of a bolt to be fitted is d [mm], an inner diameter of the counterbore hole provided on an insertion side of a screw hole is D+0.2 [mm], a pitch of a screw thread is P [mm], and θ satisfies θ=arc tan(P/d).

There is provided a nut in which occurrence of galling is prevented. The nut in which a depth t of a counterbore hole is set to be greater than (D−d×cos θ)/tan θ, when a nominal diameter is D, an average value of a maximum outer diameter and a minimum outer diameter taking into account a tolerance of a bolt to be fitted is d [mm], an inner diameter of the counterbore hole provided on an insertion side of a screw hole is D+0.2 [mm], a pitch of a screw thread is P [mm], and θ satisfies θ=arc tan(P/d).

A bone anchor includes a shank with a first end, an opposite second end, and a longitudinal axis. The shank includes a core, a thread that extends in a helix around the core and that has a lower flank directed towards the first end and an upper flank directed towards the second end, wherein the upper flank and the lower flank define a first cross-sectional thread shape, and an additional thread structure including a recess that extends together with part of the thread in the helix around the core. The thread and the additional thread structure together define a second cross-sectional thread shape different from the first cross-sectional thread shape. An axial length of the portion of the thread that has only the first cross-sectional thread shape is greater than an axial length of the entire portion of the thread that includes the second cross-sectional thread shape.

To provide a screw thread which achieves a further reduction in screwing torque while securing removability of a coating film or the like and which is capable of stabilizing conductivity. In a screw thread in which a recessed portion (7) is partially provided on a flank surface (131) of a screw thread ridge provided on a screw thread shaft main body (5), a screw thread ridge (13) in a section where the recessed portion (7) is formed is smaller than a regular screw thread ridge (3), and a ridge height (H12) in a distal end portion in a screwing direction is lower than a ridge height (H11) in a rear end portion in the screwing direction W.

To provide a screw thread which achieves a further reduction in screwing torque while securing removability of a coating film or the like and which is capable of stabilizing conductivity. In a screw thread in which a recessed portion (7) is partially provided on a flank surface (131) of a screw thread ridge provided on a screw thread shaft main body (5), a screw thread ridge (13) in a section where the recessed portion (7) is formed is smaller than a regular screw thread ridge (3), and a ridge height (H12) in a distal end portion in a screwing direction is lower than a ridge height (H11) in a rear end portion in the screwing direction W.

The coating film peeling nut of the present invention has a notch 13 formed in an inner surface of a nut main body 10 on which a female screw 12 is formed, the notch 13 extending in a direction different from that of a lead angle of the female screw 12. The notch 13 is formed helically, and a winding direction thereof is the same as that of the female screw 12. A pitch of the notch 13 is 2 to 10 times a pitch of the female screw 12, and a depth of the notch 13 is 20 to 80% of a thread height of the female screw 12.

The coating film peeling nut of the present invention has a notch 13 formed in an inner surface of a nut main body 10 on which a female screw 12 is formed, the notch 13 extending in a direction different from that of a lead angle of the female screw 12. The notch 13 is formed helically, and a winding direction thereof is the same as that of the female screw 12. A pitch of the notch 13 is 2 to 10 times a pitch of the female screw 12, and a depth of the notch 13 is 20 to 80% of a thread height of the female screw 12.

The disclosure provides a bolt including a main body, a head portion and a thread portion. The main body has a central axis. The head portion connects the main body. The thread portion is connected to the main body and runs around the central axis. The thread portion has a bearing surface facing toward the head portion. The bearing surface is a continuous curved surface or has an inflection point. The bearing surface includes a concave curved surface, a convex curved surface and a flank surface. The concave curved surface connects the main body. The convex curved surface is located further away from the main body than the concave curved surface. One side of the convex curved surface connects the concave curved surface, and another side of the convex curved surface connects the flank surface.