The ratchet thimble mechanism helps to ensure repeatable results by transmitting micro vibrations along the spindle to the contact face to provide a constant measuring force and encourage good contact with the work piece. The ratchet works from the thimble as well as the speeder so it is always easy to use even when making measurements one handed. The sound of the ratchet provides the user with a sense of confidence and the speeder enables the rapid spindle feed needed when measuring widely different dimensions.