Test specimen holder

A test specimen holder for holding a test specimen in a material testing machine applying force loads, the test specimen holder comprising:

• a base member having a piston chamber, a port and an end couplable to the material testing machine;
• a piston movable in the piston chamber;
• a pair of first and second jaw assemblies supported by the base member so as to be opposite each other, the jaw assemblies being operably coupled to the piston;
• and
• valve means for selectively, fluidly coupling the port to the piston chamber, the valve means comprising a twistable user operable knob disposed on the base member in order to minimize unwanted preloading of a test specimen secured by the test specimen holder.

A test specimen holder for holding a test specimen in a material testing machine applying force loads, the test specimen holder comprising:

• a base member having a piston chamber;
• an end plate coupled to the base member to enclose the piston chamber;
• an alignment member coupled to the end plate to align the base member with the material testing machine, the alignment member being couplable to the material testing machine;
• a piston movable relative to the piston chamber;
• a pair of first and second jaw assemblies supported by the base member so as to be opposite each other, the jaw assemblies being operably coupled to the piston;
• a valve chamber fluidly coupled to the piston chamber and coupled to the material testing machine;
• a valve stem supported by the base member coupled to the valve, the valve stem being twistable to operate the valve in order to minimize unwanted preloading of a test specimen secured by the test specimen holder;
• and
• a user operable knob coupled to the valve stem.