Method of hole forming

A dieless method of hot forming a cylindrical hole in a part of substantial thickness comprising:

• heating the part to substantially reduce the hardness therof throughout the zone in which the hole is to be formed,
• relatively moving a pair of cylindrically shaped tools having axially extending openings therein toward each other to displace and extrude material from the heated zone from opposite sides of the part into the axially extending openings in said tools until the extruded material has a thickness greater than that of the part and terminating said relative movement of the tools at depths within the part which leaves an integral annular wall section intermediate of the sides of the part having a thickness substantially less than that of the part, and
• separating the annular wall section from the part to complete the formation of a cylindrical hole through the part.

A dieless method of hot forming a cylindrical hole through a metal part of substantial thickness comprising:

• locally heating the part to substantially reduce the hardness thereof throughout a limited zone corresponding to the hole to be formed,
• relatively moving a pair of cylindrically shaped tools having axially extending openings therein to indent the heated zone from opposite sides of the part and extrude metal displaced by indenting the opposite sides of the part into the axially extending openings in the tools to form a pair of aligned cavities having a depth less than one half the original thickness of the part to define an annular wall section intermediate the sides of the part having a thickness substantially less than that of the part, and
• punching the annular wall section from the part to complete the formation of a cylindrical hole through the part.

A dieless method of hot forming a cylindrical hole through a metal part of substantial thickness comprising:

• locally heating the part to substantially reduce the hardness thereof throughout a limited zone corresponding to the hole to be formed,
• relatively moving a pair of tools having central holes therein to indent the heated zone from opposite sides of the part and extrude metal displaced by indenting the opposite sides of the part into the central holes of the tools to form a pair of aligned cavities wherein at least one of the cavities is a cylindrical groove and both cavities have a depth less than one half the thickness of the part to define a wall section intermediate the sides of the part having a thickness substantially less than that of the part, and
• punching the annular wall section from the part to complete the formation of a cylindrical hole through the part.

A dieless method of hot forming a cylindrical hole in a metal part of substantial thickness comprising:

• heating the part to substantially reduce the hardness thereof throughout the zone in which the hole is to be formed,
• relatively moving a pair of cylindrically shaped tools having axially extending openings therein toward each other to indent axially aligned cylindrical grooves having a depth less than one half the thickness of the part in the heated zone on opposite sides of the part and extrude metal displaced from the grooves into the axially extending openings of the tools to define between the grooves an integral annular wall section having a thickness substantially less than that of the part, and
• separating the annular wall section from the part to complete the formation of a cylindrical hole through the part.