A method for manufacturing a high precision hollow metallic component, by obtaining, through extruding or roll forming, a precursor hollow metallic profile having a constant cross section and at least one precursor chamber; positioning the precursor hollow metallic profile in a split-die cavity, wherein at least two walls of said split die cavity have essentially outside dimensions of corresponding walls of the high-precision hollow metallic component; introducing a mandrel made of at least two parts into the precursor chamber; plastically deforming the precursor hollow metallic profile by expanding the mandrel to obtain finished dimensions of the high-precision hollow metallic component; removing the mandrel from the finished chamber after reversing an expanding action. A variable cross section hollow metallic component, with at least two chambers obtained with the method, is also described.

According to the present invention, a conveyor pulley for use in a belt conveyor is provided, comprising: a roller tube (1); wherein the roller tube (1) is formed by plastically deforming a central portion of a substantially cylindrical metal tube (2) radially outwardly so as to form a crowned portion (4) having an enlarged outer diameter (OD.sub.ENL) with respect to remaining portions (6) of the metal tube (2).

In a method for joining bumper members, a bumper reinforcement including a rear inclined wall provided with a hole, and a bumper stay in a hollow shape are prepared. The method for joining bumper members includes the steps of: inserting the bumper stay through the hole of the bumper reinforcement to pass through the rear inclined wall; inserting rubber into the bumper stay; and compressing the rubber in a direction of an axis L of the bumper stay to expand the rubber outward from inside to expand and deform at least a portion of the bumper stay inserted into the hole, thereby joining the bumper stay to the rear inclined wall by press-fitting.

In a method for joining bumper members, a bumper reinforcement including a rear inclined wall provided with a hole, and a bumper stay in a hollow shape are prepared. The method for joining bumper members includes the steps of: inserting the bumper stay through the hole of the bumper reinforcement to pass through the rear inclined wall; inserting rubber into the bumper stay; and compressing the rubber in a direction of an axis L of the bumper stay to expand the rubber outward from inside to expand and deform at least a portion of the bumper stay inserted into the hole, thereby joining the bumper stay to the rear inclined wall by press-fitting.

A steel pipe out-of-roundness prediction method of predicting out-of-roundness of a steel pipe after a pipe expanding step in a steel pipe manufacturing process including: an end bending step; a press bending step; and the pipe expanding step, the steel pipe out-of-roundness prediction method includes a step of predicting the out-of-roundness of the steel pipe after the pipe expanding step by using an out-of-roundness prediction model having been trained by machine learning, the out-of-roundness prediction model for which an input data is data including one operational parameter or two or more operational parameters selected from the operational parameters of the end bending step and one operational parameter or two or more operational parameters selected from the operational parameters of the press bending step, and an output data is steel pipe out-of-roundness information after the pipe expanding step.

A steel pipe out-of-roundness prediction method of predicting out-of-roundness of a steel pipe after a pipe expanding step in a steel pipe manufacturing process including: an end bending step; a press bending step; and the pipe expanding step, the steel pipe out-of-roundness prediction method includes a step of predicting the out-of-roundness of the steel pipe after the pipe expanding step by using an out-of-roundness prediction model having been trained by machine learning, the out-of-roundness prediction model for which an input data is data including one operational parameter or two or more operational parameters selected from the operational parameters of the end bending step and one operational parameter or two or more operational parameters selected from the operational parameters of the press bending step, and an output data is steel pipe out-of-roundness information after the pipe expanding step.

A bead forming method includes the steps of preparing a bumper stay having a partition wall that partitions an internal space and extends in a longitudinal direction, an elastic body that can be inserted into the bumper stay, and a pusher that presses the elastic body; inserting the elastic body into the bumper stay and arranging the elastic body in the bumper stay so as not to come into contact with the partition wall; and forming a buckling bead by compressing the elastic body in the longitudinal direction of the bumper stay by the pusher to expand the elastic body outward in a radial direction without coming into contact with the partition wall, thereby bulging a part of an outer wall of the bumper stay outward in the radial direction without deforming the partition wall.

A bead forming method includes the steps of preparing a bumper stay having a partition wall that partitions an internal space and extends in a longitudinal direction, an elastic body that can be inserted into the bumper stay, and a pusher that presses the elastic body; inserting the elastic body into the bumper stay and arranging the elastic body in the bumper stay so as not to come into contact with the partition wall; and forming a buckling bead by compressing the elastic body in the longitudinal direction of the bumper stay by the pusher to expand the elastic body outward in a radial direction without coming into contact with the partition wall, thereby bulging a part of an outer wall of the bumper stay outward in the radial direction without deforming the partition wall.

Disclosed is a pipe expanding punch for a drill, which is configured to expand a pipe by hitting the pipe by an anchor drill or a rechargeable drill. The pipe expanding punch includes: an expanding mandrel provided with at least one portion (hereinafter referred to as an expanding part) having an outer diameter larger than an inner diameter of a pipe to be expanded; and a holder formed integrally with the expanding mandrel and fixedly coupled to a drill such that the pipe is expanded using the drill, wherein the outer diameter of an introduction part of an end portion of the expanding mandrel is smaller than the inner diameter of the pipe, a first tapered step is provided between the introduction part and the expanding part, and at least one polished flat surface is formed by polishing the first tapered step.

Disclosed is a pipe expanding punch for a drill, which is configured to expand a pipe by hitting the pipe by an anchor drill or a rechargeable drill. The pipe expanding punch includes: an expanding mandrel provided with at least one portion (hereinafter referred to as an expanding part) having an outer diameter larger than an inner diameter of a pipe to be expanded; and a holder formed integrally with the expanding mandrel and fixedly coupled to a drill such that the pipe is expanded using the drill, wherein the outer diameter of an introduction part of an end portion of the expanding mandrel is smaller than the inner diameter of the pipe, a first tapered step is provided between the introduction part and the expanding part, and at least one polished flat surface is formed by polishing the first tapered step.