23. Selecting different tap holder combinations by machine feed system Description of products The function of machine feed systems Fully synchronous feed (Rigid) tapping system Spindle revolution and machine feed are synchronized, a perfect thread lead and feed per revolution are realized. Feed by lead screws A better-feed condition is realized because the tap is fed by a master lead screw shaft that has the same thread lead as this tap. Feed by gear The tap is fed at the same thread lead by a combinations of gears. This creates a better-feed to thread lead condition. Asynchronous feed system Best used when the spindle rotation and the machine feed are set indepen- dently, especially, if the machine feed value cannot be accurately predicted to be that of the tap thread lead. Hydraulic or Pneumatic pressure feed system Feed is controlled by a pressure regulation system which normally results in an inaccurate feed per revolution compared to the tap thread lead. Manual feed Technical Information Feed is controlled by operator which is difficult to keep a stable amount of feed per revolution. Technical-69 840