Originally Posted by
Edward Weber
The main reason is that there is no support under the steel. With a tool anchored in the V arm and only the bevel touching the wheel, any imperfection in the wheel can be a dangerous dig in of the tool. It is easy to damage the tool or the wheel or both if rotated too far.
CBN wheels don't have that issue, mostly happens on friable wheels.
The other thing is that a SRG's bevel are not always in-line with the center of the handle. When rotating the tool, the bevel angle changes.