Ask The Expert

What you read is correct. Over-tightening grips is a common mistake many users make when trying top prevent specimen slippage when using mechanical wedge grips. Unfortunately, over-tightening wedge grips is not really an effective way to prevent test specimen slippage. In fact it can damage the grip and exert unwanted load on the specimen Mechanical wedge grips are designed to be self-tightening – the higher the tensile load, the harder the jaw faces squeeze in on the specimen. When a tension force is applied to the specimen, the tension force causes the specimen to pull downward on the jaw faces (provided there is good bite between the jaw faces and the specimen). The faces slide down through the grip body along the wedge path causing them to squeeze the specimen. Users can further minimize slippage by improving the bite through the use of proper jaw faces, ensuring the specimen contacts at least 2/3rds of the grip faces and that the faces are clean and in good condition. Grip faces are consumable items and should be replaced when damaged.