Extensometers for materials testing

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 units 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 were designed for use on flat specimens. They ensure stable contact on flat test samples due to 3-point contact.

Dual Bevel Knife Edges

(Part No. 350210V2-01)
Produced from high toughness tool steel. These knife edges are used in applications where the standard knife edges may experience excessive chipping, such as on very hard metals. They are also ideal for high modulus composites.

The dual bevel design and tougher material of construction provides a greater resistance to damage during testing. These knife edges are also recommended for biomedical testing (especially bone) where stability of the contact point can be compromised due to the softness of the test specimen. The dual bevel edge prevents slight output shifts on the sample that can result from the standard knife edges biting into the sample.

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. Longer lengths are available on special order.

Hardened Stainless Steel

(Part No. 350210-02)
These knife edges are designed to be used in environments where additional strength and 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)

bolt-on knife edges for fracture mechanics testing

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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