Does anyone knows how to test pull stud gripper force? And the standard pulling force for BT50 tapper.

I had 2 identical toyoda's horizontal MC, one of them was unstable for fine boring.

I have suspicion on tool clamping force, since i check the tapper with test bar and got only 0.004mm runout at 300mm away from spindle face.
And it has a tendency to dent pull studs more than the other machine.

Thankyou