Aluminum-alloyed ultra-high-carbon Steels (UHC-steels) display outstanding mechanical properties combined with a reduced density compared to conventional steels. Consequently, these steels show high potential for industrial applications. A widespread use of UHC-Steels containing aluminum depends strongly on efficient machining processes. Since material processing has been restricted to laboratory scale until recently, only few empirical values exist on machining. This paper is focused on the chip formation and tool wear in external turning of aluminum-alloyed UHC-steels. The mechanical loads on the tool are presented and compared to C70MnVS4, which is commonly used for powertrain components. Furthermore, recommendations for optimized cutting tools are given. The results indicate that adhesive wear and chipping are the predominant tool wear mechanisms due to high cutting temperatures and the distinct microstructure of the investigated UHC-steel.