T-720 GENERAL
The magnetic particle examination method may be
applied to detect cracks and other discontinuities on or near
the surfaces of ferromagnetic materials. The sensitivity is
greatest for surface discontinuities and diminishes rapidly
with increasing depth of subsurface discontinuities below
the surface. Typical types of discontinuities that can be
detected by this method are cracks, laps, seams, cold shuts,
and laminations.
SE-709
1. Scope
1.1 This guide describes techniques for both dry and
wet magnetic particle examination, a nondestructive
method for detecting cracks and other discontinuities at
or near the surface in ferromagnetic materials.
These are the only direct mention of "near surface" that I can find in Section V or it's referenced docs as it relates to MT. (2007)
In short, they are still only refering to surface. "near surface" is poorly defined, but getting below .1" and calling it "near surface" is asking for trouble.
Regards,
Gerald