Knife Edges for Epsilon Extensometers

All of the following knife edges will fit all models of Epsilon extensometers that use knife edges. The exceptions are high temperature extensometers that use ceramic rods, specialty extensometers that require conical point contacts, asphalt extensometers, clip-on gages, and deflectometers.

38 EXTENSOMETER MODELS are available in many thousands of variations. Our focus on helping customers has led to the development of models to cover nearly any test method.


to the materials testing community, you know we will be there to stand behind our products when your critical application requires it.

Operation of these, and all of Epsilon’s extensometers, are


using in-house calibration systems that are calibrated with Epsilon’s laser interferometer system.

Standard Knife Edges

(Part No. 350210-01)

Produced from hardened tool steel, these knife edges are used for a wide range of applications and can be used on both round and rectangular shaped specimens. These are the standard knife edges supplied with most Epsilon extensometers.

Three-Point Contact Knife Edges

(Part No. 354299)

These knife edges are recommended for flat specimens. They ensure stable contact on flat test samples due to 3-point contact. For flat specimens <10 mm wide, one standard and one single-point knife edge may be used. 

Wear-Resistant Carbide Knife Edges

(Part No. 9903-05-02)

Designed as an alternative for customers who experience slipping or accelerated wear of the standard knife edges when testing hard materials, these ultra-hard, dual-bevel knife edges will retain a sharp edge and last much longer. They are not for use with rebar. They are also extremely sharp and not suitable for applications that are sensitive to stress concentrations. Rated to 540 °C.

Knife Edges for Notch-Sensitive Materials

(Part No. 350210V2-01)

The dual-bevel design and robust tool steel construction of these knife edges make them an ideal choice for applications that tend to cause chipping damage to standard or wear-resistant knife edges at failure. As they are not as sharp as their counterparts, these knife edges are also well-suited for working with notch-sensitive applications.

Vee Knife Edges

(PART NO.9903-01-01)

Designed for use on round specimens, these knife edges will self-center the extensometer on the specimen.

Due to the contact point variation that can occur between specimens of different diameters, units with these knife edges must be calibrated with posts of equal diameter. On extensometers with longer arms, errors created by this variation are not so pronounced, but on units with shorter arms lengths, this must be taken into consideration.

Extended Knife Edges

(Part No. 350210EXT-01)

Knife edges for applications where the additional length is required, such as where the grips are very close together. Only available by special order. Requires recalibration when retrofitting an existing extensometer.

Corrosion-Resistant Stainless Steel Knife Edges

(Part No. 350210-02)

These hardened knife edges are designed to be used in environments where corrosion resistance is required. Primary applications are in biomedical testing where the knife edges may be exposed to saline solutions.

Rounded Knife Edges

(PART NO. 350210-BLUNT)

Knife edges designed for use on transverse extensometers and applications where blunt edges are required. These are primarily used on transverse / diametral extensometers such as the 3575.

Ceramic Knife Edges

(Part No. 350210C2-01)
These knife edges are typically used in low cycle fatigue applications on hard metals where metallic knife edges would likely experience undue wear. They are also used on the submersible Model 4030 extensometer to prevent galvanic corrosion between the extensometer and the test specimen.

Bolt-On Knife Edges for Fracture Mechanics

(Part No. Bolt-On Knife Edges)

Reusable bolt-on knife edges for attaching COD gages to fracture mechanics and fatigue crack growth specimens. Sold in sets of two. 30° knife edge angle. Made of nickel-plated tool steel. Includes 4x 1/4″ 2-56 screws and hex wrench. Hole size also fits M2 screws. Rated to 500 °C (932 °F).


If your unit is in need of service, calibration or repair, initiate the RMA process with us and we will be happy to assist.

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