Bone drill bit and handpiece for using the bone drill bit

A medical bone drill bit comprising:

• a metal drill shaft body configured to extend from a drilling device for drilling into living bone, the metal drill shaft body comprising a drilling section at a distal end, a clamping section at a proximal end, and a passive heat-sensitive non-numeric optical indicator, defined by a color-changing substance which changes a visible-spectrum color depending on amount of heat sensed, wherein the color changing substance changes color by more than 30 nm in the visible spectrum when a temperature shift from 40° C. to 47° C. of the metal drill shaft body occurs, the passive heat-sensitive non-numeric optical indicator is fixed to the metal drill shaft body so as to be visible to a user as the drill bit is in use on living bone, the passive heat-sensitive non-numeric optical indicator is coupled to a thermal-conducting conductor that extends from the drilling section through the metal drill shaft body when the bone drill bit is drilling into living bone, such that the passive heat-sensitive non-numeric-optical indicator changes its indication based on a change in an amount of heat at the drill bit distal end created by friction between the drill bit and living bone, so as to provide a non-numeric warning of excessive heat on the living bone during use, the metal drill shaft body comprising a reference color area adjacent to the passive heat-sensitive non-numeric optical indicator and configured to facilitate human detection and evaluation of the color of the passive heat-sensitive non-numeric-optical indicator.