Magnetic particle testing (MT) is a useful technique, typically used to detect surface cracks in ferromagnetic materials. In MT, the yoke method is mainly applied because of its easy operation. The detectability in MT depends on the magnetization intensity of the test object, which can be determined by various methods, such as tangential magnetic field measurement with a Hall probe. Japanese researchers have developed a standard test shim to examine the magnetization state of a test object [1,2]. In Japan and United States, similar standard test shims have been used for many years to determine the magnetization intensity of a test object [3–5]. In Japan, the type A standard test shim is widely used [1–3], which comprises a thin plate with soft magnetic properties. The shim has an artificial groove, which is formed by etching the center of the test shim with a chemical solution. Type A standard test shims exist with thicknesses of 50and 100 mm. The width of the groove is approximately 70–90 mm. For the type A standard test shim with 50 mm thickness,groove depthsof 7,15 and 30 mm are available. Similarly, for the type A standard test shim with100 mm thickness, groove depths of 15,30 and 60 mm are available. In order to use the type A standard test shim in MT,