Testing Tips

Get a better GRIP on Testing.

One of the most important accessories of a material tester is the grip or fixture used to secure the test specimen while testing. If the sample is not secured properly and is allowed to move or slip during a test, this will invalidate the test and compromise operator safety.
On the surface, this may seem to be a simple proposition especially if the material is relatively generic (such as paper, plastic film, foil or textile) and can be clamped easily in a set of common vise clamps. But what if the material is unique in composition and shape and requires a customized solution to secure it? Let us help you.
Learn About Grip Options for Materials TestingWhen selecting a grip/fixture solution for your testing needs, the following should be considered:
  • The type of test being performed (i.e. tensile, compression, flexural, peel, puncture, etc)
  • The material being tested
  • The dimensions of the test specimen
  • The anticipated maximum strength
  • Type of grip operation – mechanical, pneumatic or hydraulic
  • Are your trying to meet a specific, published test method (i.e. ISO, ASTM TAPPI, DIN, etc)?
    If so, often times the method will provide guidance on the design of the test fixture to use.

Click here to browse the full catalog of grips and fixtures we have available. 

Thwing-Albert can also develop custom fixtures when your test requires a specialized way to secure your sample during a test.  

Grip Options from Thwing-Albert

To learn more about some of the grip options here are some overviews of grip categories:

Vise Clamps
The most popular gripping solution is a set of vise style clamps. These offer versatility and can be configured to meet the needs of most tensile/pull applications for flat, sheet material such as paper, paperboard, plastic film, textile, nonwovens, foil, tapes, flexible packages and the like. The vise clamps can be supplied to operate mechanically, pneumatically or hydraulically. Depending on the material the jaws are available with surface textures such as smooth, rubber coated, serrated and wave pattern. The selection of the jaw surface will depend on the material being tested.  Browse Mechanical Clamps or Browse Pneumatic Clamps.

Wedge Grips
Wedge grips are a good solution for material with high tensile strength as they are designed to apply increasing clamping force when the sample is stressed. Wedge grips are typically used for metals, rigid plastics and composites and can be configured with Vee jaws to accommodate cylindrical specimens such as wire and rods.

Yarn, Cord, Wire, and Rope Grips
Often referred to as Bollard grips, these are specialized grips available in configurations to secure both flat and round samples. For filament material such as string, yarn, threads and suture material, the sample is looped around the bollard and then secured with a vise-type clamp. The larger the bollard the better it helps to distribute the stress on the specimen more uniformly and reduce premature sample rupture.

Drum/Rubber Grips
Also known as Eccentric Roller grips, these self-tightening grips are typically used for rubber and elastomeric materials that exhibit a high degree of elongation. They are available in either single or dual roller configurations.

Pincer Grips
Pincer grips are available in either spring-loaded or vise-clamping configurations depending on the material being tested and the test application. Spring loaded grips allow the user to vary the clamping pressure being exerted on the specimen and be more finely controlled. Vise style pincer grips are ideal for higher strength applications and will provide for a higher level of clamping force. Pincer grips are ideal for applications such as pulling components off printed circuit boards or clamping onto small pull tabs on lidding material in packaging applications.