An improved and reliable method for making sharp scanning tunneling microscopy (STM) tips is described. It is based on the widely used drop-off electrochemical etching procedure, here modified to improve the control of the tip shape. A second etching is applied not only to remove the oxide layer from the tip surface, but also to sharpen the STM tips further. A tip radius less than 20 nm can be obtained reproducibly. The quality of the produced tips was inspected with transmission electron microscopy, and micrographs of tips produced with different times of second etching are shown. To produce tips which are all without an oxide layer an electronic phase control unit is necessary. Even without this etch controller more than half the tips are oxide free, and then only standard laboratory equipment is used for the tip production. Review of Scientific Instruments is copyrighted by The American Institute of Physics.