Copyright Goodheart-Willcox Co., Inc. 200 CNC Manufacturing Technology Notice the following features: ■ G98: Returns to last Z position (.25″ in this case) between holes. ■ G81: Turns on spot drilling. ■ Z: Final depth of hole. Note: Different Z positions can be programmed on subsequent holes. ■ R: The rapid position in Z that spindle goes before drilling. ■ F: The feed rate while drilling. 9.8.4 G82 Cycle (Counterbore Cycle) The G82 is a cycle to create counterbores in a predrilled hole, most often made with an end mill or specific counterboring tool. The purpose is to create a flat-bottomed hole or smooth finish by adding a dwell while the tool is at the finished Z depth. G90 G54 X1. Y1. M3 S2500 (X1. Y1. is location of first hole) T1 M6 G43 H1 Z1. M8 G0 Z.25 G98 G82 Z−1. R.1 P500 F10. X2. Y2. (Second hole) X3. Y3. (Third hole) G80 Notice the following features: ■ G98: Returns to last Z position (.25″ in this case) between holes. ■ G82: Turns on counterboring cycle. ■ Z: Final depth of hole. Note: Different Z positions can be programmed on subsequent holes. ■ R: The rapid position in Z that spindle goes before drilling. ■ P: The dwell time in milliseconds. 500 milliseconds equals .5 seconds. ■ F: The feed rate while drilling. Thinking Green Recycling Tungsten Carbide Drills Machine shops collect and store worn-out tungsten carbide drills for resale. Industry recyclers pay high rates for scrap tungsten carbide and recycle it into raw material ready for new uses. Tungsten carbide is one of the most sought-after ceramic scraps because of its strength and suitability for reuse. Reselling these old tungsten carbide drills benefi ts shops economically while also saving resources. 9.8.5 G84 Cycle (Tapping Cycle) G84 allows a machinist to tap holes with a single line of programming. This is an amazing feat when you consider the intricate steps in tapping. A tap must enter a hole at a feed rate with an exact relationship to its spindle speed, go to depth, stop and reverse the spindle, and then feed out with the