G87 Back Boring cycle

                                                            The G87 Back Boring cycle is a special cycle, its practical usage is limited due to the special tooling and setup requirements. Use the G87 Cycle only if the total costs can be justified economically. The boring bar must be set very carefully, it must be preset to match the diameter required for backboring, its cutting point must be set in the spindle oriented mode, facing the opposite direction than the shift direction.

Code line for G87 Back Boring cycle:

                There are two program formats available for the G87 back boring canned cycle. Unfortunately G99 is never used with the G87 cycle.

First one using the Q, which is commonly used:

N100 G98 G87 X… Y… R… Z… Q… F…

Second one using I and J:

N100 G98 G87 X… Y… R… Z… I… J… F…

Diagram for G87 Back Boring cycle:

Steps for the G87 Back Boring cycle:

 1.       Rapid motion to XY position of the hole position.

       2.       Spindle Rotation Stop.

       3.       Spindle Orientation.

       4.       Shift OUT (OSS) by the Q value or shift by the amount and direction of I and J.  

       5.       Rapid motion to the R level, i.e., to the bottom of the hole position.

       6.       Shift IN (OSS)by the Q value or shift back in the opposite direction of I and J. 

       7.       Spindle rotation ON (M03).

       8.       Feedrate motion to the depth in Z.

       9.       Spindle rotation STOP.

      10.   Spindle orientation.

      11.   Shift OUT (OSS) by the Q value or shift by the amount and direction of I and J. 

      12.   Rapid motion to the Initial level, i.e., to the top of the hole position.

      13.   Shift (OSS) IN by the Q value or shift back in the opposite direction of I and J. 

      14.   Spindle rotation ON.