| 摘要 |
A hole sizing tool uses a swaging tap to move material which deforms the sides of a generally cylindrical hole toward the axis of the cylinder and is followed by a portion of the tool having a generally flat flaced helical spiral configuration with the turns increasing in radius as the tool advances but with all portions of the surface of the helical spiral including lines parallel to the axis of the tool whereby only radial forces are exerted by said portion to force the sides of the hole gradually toward a final diameter larger than that left by the tap but smaller than the original dimension. In an alternate form of the tool the flat surfaces of the helical spiral are inclined slightly, so that the edge of such surface nearest the nose of the tap is at a slightly greater radius than the edge of the turn nearest the tool in which the tap is held, to generate a slight axial force tending to pull the tool into the work. The portion of the tool following the helical spiral is a smooth burnishing surface for the purpose of burnishing the hole to final size and finish. Both the increasing helical spiral portion and the constant size burnishing portion desirably have the periodic increases in radius (or lobes) characteristic of the threads of a swaging tap, but without thread crests and roots. If desired, the nose of the tap may have a cylindrical lead portion for alignment, particularly if the tool is not intended for blind holes.
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