Years ago, we were working with a VERY LARGE company on optimizing their tooling. They were having severe fretting on the tapers, One thing we noticed is that their pull studs could not be screwed into the toolholders by hand. This is a tell tale sign. We brought in a ring gage to prove that the knob threads were out of spec. But, it could also have been the toolholder, so inspecting incoming holders and pull studs with a thread and ring gage is a good practice.
Additionally, the guy in the tool crib (I hope he has retired and is not on LinkedIn) welded a 4 foot cheater bar to the retention knob socket. To remove a knob he installed, we had to heat the shank in a shrinker. Despite what we told him, he wouldn't even consider using a torque wrench. So, the next time we came in, we brought with us a NASCAR logo'd pneumatic impact wrench with a retention knob socket, but in between we installed what is pictured below, a torque limiting adaptor (they are known as torque sticks). They are made with different shaft OD's and will twist when its designated torque rating is reached. The tool crib guy wailed away on the knobs with his new gun and the problem was fixed.
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