Jaw Face Selection

[00:10] A critical part of getting accurate tensile test results is making sure the grips don't influence the outcome. The jaw faces you choose play a major role in that.

[00:19] In this video, we'll break down the most common jaw face types used on side-acting and manual wedge grips up to 150 kN and help you choose the right option for your material.

[00:31] Let's start by discussing the jaw face options for side-acting pneumatic and manual grips.

[00:36] The pneumatic grips option offers a constant preset clamping force throughout the entirety of the test.

[00:42] Both the pneumatic and manual side-acting grips use the same type of jaw faces, which come in a wide range of styles and sizes. The right choice depends on both the material and the geometry of your specimen.

[00:55] For stiff, hard materials like metals, rigid plastics, and composites, or for material with thicknesses over 1 millimeter like elastomers, serrated jaw faces are typically the best choice. Their teeth provide a strong mechanical bite that helps prevent slippage while the material elongates.

[01:12] For softer or more delicate materials, including thin films, textiles, or other flexible materials, rubber-coated faces generally provide enough friction between surfaces while minimizing damage when the grips close.

[01:25] Smooth jaw faces are ideal for thin materials, such as paper or anything stronger than a typical film, where the flat, metallic gripping surface provides enough hold without damaging the specimen.

[01:36] Smooth and rubber faces can typically be used interchangeably, but rubber can be better for more fragile materials.

[01:43] If you're seeing signs of slippage during the test, or if you're working with extremely delicate materials such as thin films, you can pair a line-contact face with a rubber or smooth face.

[01:53] The rounded line-contact face reduces the amount of contact on the specimen. This helps to reduce the amount of extrusion.

[02:01] For engineered or coated textiles, wave profile faces are best to increase the surface area of contact. This added contact helps prevent the material from slipping during the test.

[02:12] And for round specimens, vee-serrated faces provide four points of contact for improved clamping and stability.

[02:19] You may need more than one jaw face size to properly grip specimen tabs with different diameters.

[02:24] When using manual wedge grips, there are fewer jaw face styles, but they're well suited for wires, plastics, metals, composites, and elastomers.

[02:33] Wedge grips naturally increase the clamping force as the test runs, which can help reduce slippage compared to the side-acting grips.

[02:40] The most common wedge grip faces are flat serrated, which are available with different tooth densities.

[02:46] Faces with 16 teeth per inch have larger teeth and provide a stronger bite, making them ideal for harder materials like steel.

[02:55] Faces with 25 teeth per inch use smaller teeth with a lighter bite, which is more suitable for softer materials such as plastics or soft metals like aluminum.

[03:04] When testing fragile specimens such as untabbed composites, surfalloy faces offer a high friction option without the tooth penetration.

[03:13] And finally, vee-serrated faces are used for round specimens, improving contact and clamping reliability.

[03:20] No matter what grip type you're using, it's important that your specimen tab engages at least 75% of the jaw face length. This helps prevent jaw face pivoting and minimizes the chance of slippage.

[03:32] This has been a quick look at jaw face selection for testing up to 150 kN. For additional support, contact your local Instron^® Sales Engineer or visit instron.com, and make sure to subscribe to our YouTube channel for more testing tips. Thanks for watching!