G74 Reverse Tapping cycle

                                        The G74 Gcode cycle is the standard reverse tapping cycle used for the Left hand thread in a hole. At the start of the cycle the Reverse spindle rotation M04 must be In effect.  The machine switches on the control panel cannot be accessed until the cycle of thread is completed. As said in G84 the spindle speed and the feed of the lead thread is very important, these relationship must be maintained at all the times of the tapping cycle.

Code line for G74 Tapping cycle:

N100 G98 (G99) G74 X… Y… R… Z… F…

Diagram for G74 Tapping cycle:

The cycle is the standard reverse tapping cycle used for the Left hand thread in a hole. At the start of the cycle the Reverse spindle rotation M04 must be In effect.  The machine switches on the control panel cannot be accessed until the cycle of thread is completed. As said in G84 the spindle speed and the feed of the lead thread is very important, these relationship must be maintained at all the times of the tapping cycle

Steps for the G74 Tapping cycle:

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

       2.       Rapid motion to the R level, i.e., to the top of the hole position.

       3.       Feedrate motion to the depth of the thread in Z with CCW Spindle rotation (M04).

       4.       Spindle rotation stop in bottom of hole.

       5.       Spindle Clockwise rotation (M03) and back in feedrate to R level.

       6.       Spindle rotation Stop.

       7.       Spindle rotation Reverse (M04) and Rapid retract to the initial level (with G98) or Rapid retract to R            level (with G99).