Method of and machine for grinding internal threads

DETAILED DESCRIPTION I claim: 1.
A method of grinding an internal thread having a predetermined lead angle, especially a ball thread, in a rotary workpiece by means of a grinding wheel which is mounted on a rotary grinding spindle, comprising the steps of introducing the grinding wheel into the workpiece and maintaining the axes of the grinding spindle and the workpiece at a predetermined grinding angle smaller than the lead angle; and thereupon dressing the grinding wheel including correcting the profile of the grinding wheel, said correcting step comprising contacting the grinding wheel with a rotary diamond profiling tool including maintaining the axes of the profiling tool and grinding wheel at a predetermined dressing angle greater than the lead angle of the internal thread.
2.
The method of claim 1, wherein said dressing step includes maintaining the axis of the profiling roll in a horizontal plane.
3.
The method of claim 1, wherein said maintaining step includes locating the axis of the workpiece in a horizontal plane.




Description:
BACKGROUND OF THE INVENTION The invention relates to improvements in methods and machines for grinding internal threads, especially ball threads.
Presently known machines for grinding internal threads in nuts and other types of workpieces normally employ grinding wheels which are made of corundum.
Such grinding wheels are dressed, almost invariably, with radius dressing tools employing a single-point diamond.
If, in some rare instances, the grinding wheel is dressed with a diamond profiling roll, the inclination of the axis of the roll with reference to the axis of the grinding wheel must conform to the lead angle.
In the course of the grinding operation, the axes of the workpiece and grinding wheel also make an angle which equals the lead angle of the thread to be ground.
Thus, when the working surface of the grinding wheel is being dressed by a diamond profiling roll, the axis of the dressing roll is parallel to the axis of the grinding wheel