NDT custom reference standards

EDM notch shapes

Knauer & Rösch is highly-specialized in producing artificial discontinuities known as electrical discharge machined (EDM) notches. EDM notches are typically produced from an otherwise acceptable production item supplied by the manufacturer of the part or the test lab performing the inspection. When selecting what type of EDM notch is right for your application, it is important to consider both the width and length cross-section of the notch. There are various geometries available that all have their purpose for testing applications.

wide min: 0.13 mm 30mm depth – wide 0.8 mm
Corner Radius 0.03 mm


Square Notch

This notch has parallel-sided walls and minimal corner radius at notch bottom from 0.03 mm. Minimal wide of notches are 0.13. With increasing depth, the min wide of notch is increasing by some 1/100 (example: with depth 30 mm the min. wide is 0.8 mm).


This notch has parallel-sided walls at the entry surface and a corner radius at notch bottom.


This notch has angled side walls that meet at the notch bottom. Typical V-notch included angles (a) are 40°, 45°, 60°, 70°, 75° and 90°.

Wire EDM Notch

This notch is made using a wire EDM machine instead of a sinker EDM. Our wire machine allows for extremely narrow notches (down to 0.4 mm wide).

"Crack-Like" Notch

A variant of the wire EDM Notch. The Crack-Like Notch is made via wire EDMas well. The wire EDM can be programmed as the customer requires. The options are nearly endless!

Stepped Notch

This unique notch type is typically used when burning to extreme depths, where a narrow reflecting surface is needed at the bottom of the notch.