We investigated the form of the shavings obtained during turning on a lathe and also the roughness of the surface thus produced in 50G, 30KhGSA, 30KhGSN2A, and 50KhN steels melted from pure charges.* The chemical composition of the steels corresponded to the GOST 4543-71 standard. The blanks were turned on a standard lathe by a hard alloy tool made of a reground T15K6 steel slab. The turning speed was equal to 38 m/min and the frequency of the spindle was 2000 rpm, the depth of cut was 0.5 mm, and the feed was 0.2 mm/rev. The final diameter of the machined samples was 6 ram. Preliminary heat treatment of the blanks was carried out under the following conditions: I) complete annealing at 820900°C for 1 h, slow furnace cooling to 650°C (Vcool = 30°C/h), and then cooling in air; II) incomplete annealing at 740-760°C for 1 h, cooling to 650°C (VeooZ = 30°C/h), cooling in air; III) low-temperature annealing at 680-730°C for 3 h, cooling in air; and IV) improvement: quenching from 820-900°C (0.5 h) in oil, tempering at 700-720°C (3 h), cooling in air. The above temperature ranges are overall values for the steels investigated. The specific temperatures for each steel were located within these ranges. The surface roughness values (Ra and Rz) were measured with a T1000 profilograph-profilometer manufactured by "Hommel Werke" (FRG). Then the class of cleanness of the surface (see Table 1) was determined. Classes 4-6 belong to semiclean treatments whereas class 7 belongs to clean treatment (this class is usually achieved by fine turning at high cutting rates). It can be seen that, upon turning the blanks subjected to a prior heat treatment, the surface is the smoothest in spite of the low cutting speed. In the majority of the cases, fine fragmented chips were formed and no "build up" was observed on the cutting edge of the instrument. Conclusions. 1. At a constant cutting rate of structural steels, optimum results with regard to the cleanness of the surface and the form of the shavings formed are obtained after a prior thermal heat treatment. Annealing (complete, incomplete, low-temperature) produces worse results. 2. After the thermal improvement, the surface becomes cleaner even for low rates of cutting. 3. Under identical conditions of cutting, in the majority of the cases the surface is found to be cleaner for steels with higher carbon content.