Universal dressing roller and method and apparatus for dressing cup-shaped grinding wheels

A method for dressing a cup-shaped wheel used for grinding teeth on a workpiece, the wheel having inside and outside working surfaces inclined at respective pressure angles with respect to an axis of rotation of the grinding wheel, comprising the steps of:

• providing a cylindrical dressing roller mounted for rotation about an axis and having (a) an outer cylindrical dressing surface parallel to said axis, (b) an end dressing surface extending radially from said axis, and (c) a radiused rim portion between said cylindrical and end surfaces;
• rotating the grinding wheel and dressing roller about their respective axes in the same direction when dressing the inside and outside working surfaces of said grinding wheel;
• positioning said dressing roller in a first orientation relative to said grinding wheel so that part of the roller's outer cylindrical surface contiguous with said rim portion contacts one of said working surfaces at a predetermined clearance angle;
• moving the roller and wheel relative to each other to move said point of contact along said first working surface for dressing same;
• positioning said dressing roller in a second orientation so that a part of the roller's radially extending end surface contiguous with said rim portion contacts the other working surface of said grinding wheel at a predetermined clearance angle;
• and
• moving the roller and wheel relative to each other to move said second point of contact along said other working surface for dressing same.

An apparatus for dressing a cup-shaped grinding wheel mounted on a machine for grinding teeth on a gear-shaped workpiece, said apparatus including a dressing tool mounted for rotation about an axis adjustable to preselected angular orientations relative either to the inside or outside working surfaces of a cup-shaped grinding wheel, the improvement wherein said dressing tool is formed in the shape of a modified cylinder having an outer surface, an end surface and a radiused rim portion connecting said outer and end surfaces;

• and wherein said dressing tool is positioned so that, when dressing the inside working surface of said grinding wheel, part of said outer surface contiguous with said rim portion contacts the grinding wheel, and further, when dressing the outside surface of said grinding wheel, part of said end surface contiguous with said rim surface contacts the grinding wheel, and wherein, when said surfaces of the dressing tool are oriented, respectively, relative to said working surfaces of the grinding wheel, predetermined clearance angles are provided between the respective surfaces of said tool and said grinding wheel, said dressing tool further including at least one of (a) said outer surface extending at an angle less than parallel relative to said axis of said tool, the amount less than parallel being equivalent to one of said predetermined clearance angles and (b) said end surface of said dressing tool extending at an angle less than perpendicular relative to said axis of said tool by an amount equivalent to one of said clearance angles.