The double capstan grips can be used to grip threads and thread-like tensile
With this deflection principle a force slope occurs in two stages. The specimen break takes place in the gage length without causing slippage of the specimen on the lower roller or jaw breaks.
The specimen is looped over the load cell roller. The specimen is then deflected to a lower roller and guided to a third height-adjustable roller.
After the deflection of the double thread, a pre-load weight (not included in scope of delivery) is attached. During this stage all three rollers are movable. The extensions, which are created when the pre-load weight is attached, are balanced. The three lengths are aligned to the material being tested.
The double thread is clamped into the wedge grip. This is also height adjustable.
After the specimen grip is closed the deflection rollers are locked. Frictional forces between the rollers and the specimen prevents slippage of the specimen. The roller diameter is dimensioned in such a way that the occurring friction does not influence the test results.
A specimen grip with constant gripping force is used to clamp the double thread because the specimen to be tested can frequently slip out from between the gripping areas.