System and method for cracking a connecting rod

1 . A method for creating a cracking line in a connecting rod, the method comprising:

etching, using a first pass of a laser, a groove in an inner surface of a larger bore of the connecting rod by removing material from the inner surface, the groove being discontinuous, including a plurality of holes that are spaced apart and that have different depths, and including at least a first segment containing a first group of holes, a second segment containing a second group of holes, and a third segment containing a third group of holes; and

removing more material from the groove using a second pass of the laser with a different number of laser pulses for each of the first segment, the second segment, and the third segment to increase the depths of the holes to a different depth for each of the first segment, the second segment, and the third segment, thereby increasing a stress concentration factor of the groove.

2 . The method of claim 1 , wherein the holes are spaced apart by 0.04 millimeters.

3 . The method of claim 1 , wherein the groove has a general V-shape.

4 . The method of claim 1 , wherein the connecting rod includes two grooves on opposing sides of the larger bore, wherein a first groove has a general V-shape and wherein a second groove has a general inverted V-shape, wherein the general V-shape and the general inverted V-shape indicate a correct realignment of separate components of the connecting rod after cracking.

5 . The method of claim 1 , wherein the groove is etched at a 30° angle with respect to a plane defined by the surface upon which the connecting rod is placed and wherein the holes are angled 30° with respect to a plane defined by the surface upon which the connecting rod is placed.

6 . The method of claim 1 , further comprising:

using the cracking line, cracking the connecting rod into a connecting rod shaft and a connecting rod cap;

installing a bearing to the larger bore; and

re-assembling the connecting rod by connecting the connecting rod shaft to the connecting rod cap.

7 . A method for creating a cracking line in a connecting rod, the method comprising:

etching, using a first pass of a laser, a groove in an inner surface of a larger bore of the connecting rod by removing material from the inner surface, the groove being discontinuous and including a plurality of holes that are spaced apart and that have different depths;

removing more material from the groove using a second pass of the laser to increase the depths of the holes, thereby increasing a stress concentration factor of the groove, wherein the groove includes a first groove segment containing a first group of holes, a second groove segment containing a second group of holes, and a third groove segment containing a third group of holes; and

using the first pass of the laser:

etching the holes of the first groove segment using five pulses to achieve a depth of 0.38 millimeters for the first group of holes;

etching the holes of the second groove segment using six pulses to achieve a depth of 0.45 millimeters for the second group of holes; and

etching the holes of the third groove segment using four laser pulses to achieve a depth of 0.32 millimeters for the third group of holes.

8 . A method for creating a cracking line in a connecting rod, the method comprising:

etching, using a first pass of a laser, a groove in an inner surface of a larger bore of the connecting rod by removing material from the inner surface, the groove being discontinuous and including a plurality of holes that are spaced apart and that have different depths;

removing more material from the groove using a second pass of the laser to increase the depths of the holes, thereby increasing a stress concentration factor of the groove, wherein the groove includes a first groove segment containing a first group of holes, a second groove segment containing a second group of holes, and a third groove segment containing a third group of holes; and

using the second pass of the laser:

etching the holes of the first groove segment using an additional five pulses to increase the depth of the first group of holes to 0.45 millimeters;

etching the holes of the second groove segment using an additional six pulses to increase the depth of the second group of holes to 0.51 millimeters; and

etching the holes of the third groove segment using an additional four pulses to increase the depth of the third group of holes to 0.37 millimeters.