Patent Number: 051587408
Section: abstract

A trepan is provided in a flat end face of an end plug about an external opening of an axial bore through the end plug. The trepan includes an annular groove encircling the external opening and an annular end face portion extending between the annular groove and the external opening. The ratio of the depth of the groove to the diameter of the annular end face portion of the trepan is within a range of from about 1:3 to 1:6. The ratio of the depth of the groove to the width thereof is within a range of from about 1:1 to 1:2. When an axially-directed welding arc is applied to the trepan in the flat end face of the end plug a melting of the material of the trepan into the end face occurs which forms a weld seal such that the trepan is replaced by a shallow concavity overlying the weld seal and extending across the region substantially encircled originally by the annular groove of the trepan.