Exchangeable measuring-rod type small-bore groove depth measuring tool

The utility model relates to an exchangeable measuring-rod type small-bore groove depth measuring tool which comprises a ruler body, a measuring rod, a spring, a rear cover and a measuring rod seat. The exchangeable measuring-rod type small-bore groove depth measuring tool is characterized in that a through hole is arranged at the center of the ruler body in the length direction; one end of the through hole is blocked by the use of the rear cover; the spring and the measuring rod seat are successively packaged in the through hole; the bottom end face of the measuring rod seat is contacted with the spring; the measuring rod is threadingly connected at the top of the measuring rod seat; the measuring rod extends out of the ruler body; an observation window which communicates with the through hole is arranged in the length direction of the ruler body; a scale is disposed at one side of the observation window on the ruler body; and the measuring rod seat is provided with a measuring rod seat scale which fits with the scale of the ruler body. The utility model has advantages as follows: as vernier principle is adopted to measure the groove depth of a small-bore groove part, the precision can reach 0.05mm; the exchangeable measuring-rod type small-bore groove depth measuring tool has strong versatility and has a simple structure; and the measuring rod has small diameter and has good interchangeability.