The coefficient of friction during upsetting under semi-dry conditions is measured using the ring compression test. A small amount of mist lubricant is sprayed onto the mirror surfaces of cemented tungsten carbide (WC) tools, and pure aluminium specimens are compressed by the tools. It is found that spraying a small amount of lubricant (0.5 g/m²) reduces the friction effectively. The roughness of the workpieces after compression increases as the amount of the lubricant increases to R_a = 0.20—1.0 μm which is in the same order as the lubricant film thickness. Mist lubrication results in very small dots of lubricant particles sticking to the tool surface, and the lubrication mechanism of mist lubricant is discussed.