In an internal grinding machine, it is common practice to provide for the occasional dressing of the abrasive wheel. Usually, this dressing operation involves the removal of a small layer of the material from the surface of the wheel to expose new abrasive particles. This is because (even in a diamond wheel) the cutting particles that protrude from the matrix become worn and the wheel becomes dull. Not only does such dullness produce a slower cutting cycle, but it produces forces on the wheel and on the spindle that distort the geometry of the finished surface. The usual method of dressing is to use either (1) a single point dresser, such as a large diamond that is passed axially along the cylindrical abrasive wheel and actually cuts the wheel and removes approximately 0.001 inch from its surface, or (2) a rotary dresser consisting of a cylinder similar in shape to the grinding wheel itself formed with a matrix in which large particles of diamond have been embedded. What this means is that the rotary dressing wheel is simply made of a harder substance than the abrasive wheel (which is also rotating) and, while each wheel removes a certain amount of material from the other, the dressing wheel removes more material from the abrasive wheel than vice versa. The fact that the abrasive wheel must be traversed longitudinally across the diamond means that a substantial part of the time used in the grinding cycle is consumed in this unproductive dressing procedure. Furthermore, the wear on a single-point diamond dresser produces a "drift" in the size of the finished workpiece. The complex mechanism necessary to support the rotary-type dresser also introduces inaccuracies as well as considerable cost. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a grinding machine having a dresser which is capable of being mounted very close to the work area so that the run-out of the abrasive wheel for dressing is short.
Another object of the present invention is the provision of an internal grinding machine having a dressing mechanism which is simple in construction and inexpensive to manufacture.
A further object of the present invention is the provision of an internal grinding machine having a dresser which is firmly mounted, so that it does not introduce inaccruracies to the surface of the abrasive wheel during dressing due to moving of its mount.
It is another object of the instant invention to provide a dressing mechanism for an internal grinding machine which can be readily adapted to use on an older machine for replacement purposes.
A still further object of the invention is the provision of an internal grinding machine with a dressing mechanism which is subject to very little wear and involves no complex mechanisms.
Another object of the present invention is the provision of an automatic grinding machine having a dresser capable of a long life of useful service with a minimum of maintenance.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.