The study investigates machine tapping of threads in aluminium alloy Al 6082 using commercially available taps with DLC and conventional coatings. Seven M10 × 1.5 taps were tested under flood lubrication, minimum quantity lubrication (MQL), and dry conditions. The comparison was based on average tapping and withdrawal torque, while thread-flank line roughness was additionally measured for the Garant 13110 and Guhring 8082 taps. Flood lubrication produced the lowest and most stable tapping torque. Under MQL, the torque values were slightly higher, but lubricant consumption was substantially lower. Dry tapping proved unreliable because most tools failed due to aluminium adhesion and chip clogging. Among the DLC coated tools, Garant 13110 and Guhring 8082 achieved particularly favourable results. Roughness measurements showed that R$_{a}$ and R$_{z}$ increased as the amount of lubricant decreased, while Guhring 8082 achieved lower roughness than Garant 13110 under all three lubrication conditions. The results indicate that the effectiveness of a DLC coating also depends on the intended tool application and lubrication conditions.
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