Most holder discussions stop at the taper, but the pull stud deserves equal attention in through-coolant machining. Once drawbar force, coolant passage design, and actual cutting load come together, the small part at the back of the holder stops being a detail. It becomes part of the system’s structural limit.
That is why some SK holders are paired with CAT-style pull studs. The reason is not appearance or naming preference. It is usually about section strength and how the pull stud behaves under clamping load when coolant also needs to pass through the center. If a slimmer form leaves too little support in the stressed area, the weak point moves to the wrong place.
Why the geometry matters more in through-coolant work
Through-coolant holders already ask more from the rear connection because the internal passage changes the available material around the load path. Under higher drawbar force, that difference becomes more meaningful. A shorter or thicker CAT-style pull stud can make better sense when the machine and holder arrangement put more demand on that section.
Heavy machines expose weak details faster
This becomes easier to understand on rigid boring or heavier CNC platforms. Stronger machines do not create the weakness, but they do expose it sooner. If the holder system is being pushed hard, small structural differences in the pull stud no longer stay theoretical.
Review the holder system as a complete assembly
The taper, the pull stud, the coolant route, and the actual cutting load belong in one conversation. That is especially true when the job uses special holders, boring tools, or other application-led assemblies. If the needed holder format sits outside common catalog combinations, the Custom Tools section is the right starting point. For machine-specific review, the Full RFQ page is the cleaner path because the taper, drawbar, coolant, and machine details all need to be read together.