RT Journal Article SR Electronic A1 Popov, Alexey A1 Khramenkov, Mikhail T1 Effect of Hydraulic Oil Entering the Cutting Fluid on the Tool Life and Roughness in Milling of Structural Steel JF Manufacturing Technology Journal YR 2019 VO 19 IS 3 SP 482 OP 486 DO 10.21062/ujep/316.2019/a/1213-2489/MT/19/3/482 UL https://journalmt.com/artkey/mft-201903-0021.php AB Thanks to their chemical and physical properties, the cutting fluids can significantly affect the process of machining - the use of cutting fluid reduces the roughness of the machined surface and increases the tool life. However, during the machining the oil from the hydraulic system of the machine often gets into the cutting fluid, which can alter the properties of the cutting fluid. In scientific literature there is no information on the effect of the hydraulic oil entering the cutting fluid on the tool life and roughness in machining of the structural steel. In this regard, at the laboratory of the Department of Machining and Assembly of the Technical University of Liberec, there has been conducted a study to ascertain the effects of hydraulic oil getting into different types of cutting fluids during the milling of structural steel.