MTS Series 646 Hydraulic Collet Grips - Manual (Page 17)

Series 646 Hydraulic Collet Grips Introduction 17
distributed between the surfaces of the spiral washers and the stud in a ratio of
the relative stiffness of the parts. The spiral washers have a large surface area and
therefore greater stiffness. They react to most of the load and keep the stress in
the stud below its fatigue runout level.
Couplings
Special upper and lower couplings clamp the grips to the actuator and force
transducer for axial-torsional grips. Each coupling has two different thread
patterns; a right hand thread with a pitch of 3 mm and a left hand thread with a 2
mm pitch. Half of the coupling matches the thread of the grip and the other half
matches the thread of the actuator or force transducer adapter. Each coupling is
marked to indicate which direction to tighten it and how much torque to lock it
down.