Wedge action grips induce a wedging action as the jaw inserts slide relative to angled interior walls of the grip ‘chamber’ or grip body. As the jaws close, the clamp force to the test specimen increases both during test sample installation and the test loading.

Mechanical wedge action grips are more popular than power assisted pneumatic or hydraulic action grips because they are generally more compact, more affordable, and simpler to use. Power assist is very beneficial in higher force testing applications.

Mechanical wedge action grip feature either stationary grip bodies or stationary jaw inserts. Stationary grip bodies are coupled to the test machine and remain fixed. The jaws move during opening and closing and sample insertion. Wedge grips with stationary jaw inserts reduce or eliminate undesirable axial compressive loads that can cause sample damage as they are tightened. Stationary jaws clamp the sample without requiring axial movement. With some stationary jaw grips, handles turn a collar that moves the grip body. The jaw inserts couple directly to the test frame. Note that achieving the same goals is possible using adjustable jaws (fixed grip), with a more inconvenient sample loading procedure.

Wedge angle is typically small (e.g. 10-15 degrees) which limits the range of opening or sample thickness range with a jaw inserts. Multiple jaw inserts are then needed to cover multiple sample thicknesses.

All wedge action grips perform tensile tests. In fatigue testing applications, selected grips can perform tension-tension fatigue tests. Hydraulic action wedge grips can perform tension-compression, through zero loading, or compression-compression tests because of their design. The wisest path to selecting the best grip for your applications is to contact our applications engineer who will help you select or design a solution for you.

Please call us at 1.800.430.%6536 to speak with an applications engineer.