A guide (12) for setting the depth of cut of a rotary cutting tool, or other hand-held power tool, which automatically locks into a desired position to set the depth of a cut without requiring manual operation of a locking knob or similar structure. The depth guide is released from the locked position by actuation of a release switch (94). The depth guide includes a depth guide base (50), a depth guide shaft (52) attached to the depth guide base, and an automatic locking and release mechanism (54) coupled to the depth guide shaft. The automatic locking and release mechanism and depth guide shaft may be mounted in a handle (24) of the hand-held power tool, such as a detachable handle, for mounting the depth guide to the tool.