The drills with internal cooling system should be used also with external cooling. Drill speed should be controlled from 600rpm(thick drills) up to 1000rpm(for fine drills).
Cutting efficiency is coming bad by each use and bad drill will cause heat damages against bone. Only good drills should be used for operation. For very hard bones, it is recommended to use surgical burs prior to implant drills.
Surgical burs will help easy drilling and long life. The fix screw of drill stopper is so small and it can not be bear a strong force. Drills can be used also without stopper.