A pull stud is a threaded component in a CNC machine that secures a tool holder to the spindle. It acts as a connection point for the machine’s drawbar, which pulls the tool holder tightly into the spindle taper to withstand severe cutting forces. Pull studs are critical for preventing tool holders from dislodging and must be the correct style, size, and be properly installed to avoid damage, as they are not interchangeable between all machines.
Function and purpose
- Secures the tool holder: The pull stud is screwed into the end of the tool holder.
- Connects to the drawbar: The machine’s drawbar grips the pull stud to pull the tool holder into the spindle.
- Withstands cutting forces: It must be strong enough to resist powerful forces generated during machining.
Key characteristics and variations
- Standards: They are manufactured to specific standards, such as BT, CAT, SK, or DIN, which are not always interchangeable.
- Size: Pull studs come in different sizes (e.g., BT30 vs. BT40), and using the correct size is essential for a secure fit.
- Coolant-through capability: Some pull studs have a through-hole to allow for “through-tool coolant” delivery to the cutting edge.
- Material: High-strength materials are used to prevent breakage under high stress.
Importance of proper use
- Machine damage: Using the wrong or improperly installed pull stud can lead to spindle damage.
- Reduced tool life: An incorrect pull stud can cause poor performance and reduce tool life.
- Poor surface finish: A secure, interference-free fit is required for a quality cut, so an improperly installed pull stud can lead to poor surface finish.
