A trimmer gauge for a case trimmer. The trimmer gauge may include a fixed-length shaft that is a threshold length of a case and sized to precisely set a blade extension distance for a case trimmer. A first end of the fixed-length shaft may be flat and a second end of the fixed-length shaft may be tapered. At least a portion of an outer surface of the fixed-length shaft includes a first groove located a threshold distance from the first end. The groove may be shaped to receive arms of a collet of the case trimmer.