Steep taper Large manual machines and CNC machines use toolholders that have been precisely ground with a male taper that mates with the machine’s speci c female taper. There is also a way to secure the toolholder in place with a pull stud or a draw bar thread. With CNC machines, the pull stud is more popular because it allows for easier automatic tool changing. A toolholder consists of ve basic components: Pull stud Tapered shank Gripper groove: circular groove Adapter Opposed Slot Tapered shank The standard de nes six basic taper shank sizes including SK 30, SK 35, SK 40, SK 45, SK 50, and SK 60. The proper Taper Shank for the Type of Machine ISO 60 Very large machines ISO 50 Medium size machines ISO 40 Small size machines ISO 30 Very small machines j i Coolant supply form AD/B Toolholders form AD/B have internal coolant supply. To use form B (coolant supply through the collar) the two headless screws must be removed and a sealed pull stud must be inserted. To use form AD (central coolant supply) the two headless screws must remain at the collar and a pull stud with drill through must be inserted. j.23