Grinding is generally used in the final step of machining metallic materials to achieve the necessary surface quality and dimensions. Grinding wheels with flat surfaces are commonly used in the process of grinding. However, due to the fact that there is a great deal of contact length (corresponding to the grinding-wheel width) between the grinding wheel and the workpiece, effective cooling during the grinding process may not be possible and, consequently, the heat in the deformation region is increased. Due to these reasons, some undesired results such as an unqualified surface and a roundness error take place. Various profiles of the grinding wheel were, therefore, proposed to improve the surface quality and decrease the roundness error by modifying the grinding wheel and developing various methods. In this study, AISI 1050, AISI 4140 and AISI 7131 steel materials were subjected to the cylindrical-grinding process using wheels helically grooved at 15°, 30°and 45°and the obtained results such as the average surface roughness and roundness errors were compared with the results of the flat-surface grinding wheels. The experimental results show that the surface roughness and roundness error are reduced when using a helically grooved grinding wheel and, thus, the quality of the machined parts is improved. Keywords: cylindrical grinding, helically grooved grinding wheel, roundness error, surface roughness Bru{enje se navadno uporablja kot kon~na stopnja obdelave kovinskih materialov za zagotovitev kvalitete povr{ine in mer. Pri postopku bru{enja se navadno uporabljajo brusni koluti z ravno povr{ino. Vendar pa je zaradi velike kontakne dol`ine (odvisno od {irine brusilnega koluta) med brusilnim kolutom in obdelovancem ote`eno u~inkovito ohlajanje, zato se podro~je deformacije ogreva. Lahko se pojavijo ne`eleni rezultati, kot so neustrezna povr{ina in napaka okroglosti. Za izbolj{anje kvalitete povr{ine in zmanj{anje napak okroglosti so predlagani modificirani brusilni koluti z razli~nimi profili in razli~ne metode. V tej {tudiji so bila jekla AISI 1050, AISI 4140 in AISI 7131 okroglo bru{ena s koluti z vija~nim utorom 15°, 30°in 45°. Dobljeni rezultati, kot sta povpre~na hrapavost povr{ine in napaka okroglosti, so bili primerjani s tistimi, dobljenimi z brusilnimi koluti z ravno povr{ino. Rezultati ka`ejo, da se povr{inska hrapavost in napaka okroglosti zmanj{ujeta pri uporabi brusilnih kolutov z vija~nim utorom, torej se kvaliteta strojnih delov izbolj{a. Klju~ne besede: okroglo bru{enje, brusni kolut z vija~nim utorom, napaka okroglosti, hrapavost povr{ine