A map describing the flank wear characteristics of uncoated high-speed steel (HSS) tools is constructed under the condition of drilling die-cast aluminum alloy. Several wear mechanisms are revealed which describe different wear modes observed by SEM in uncoated HSS tools, including adhesive wear, adhesive and abrasive wear, abrasive wear, severely plastic flow, and thermal wear. In the map, there exists a minor wear region, which is called ''safety cutting zone'' to the HSS tools. This map will be a good reference for choosing suitable drilling parameters of uncoated HSS cutting tools.