Drilling operations have an important role in manufacturing industries and the application range is about 33% among the machining methods. In drilling processes, hole quality is affected by workpiece material, drilling parameters, drill diameter, drill bit features. In this study, the surface quality of the hole and the drill bit wear were investigated experimentally when drilling AISI 1040 steel and Al7075 aluminum workpieces with twist drills. Three different types of twist drill bits (polished, rolled and TiN coated) with diameters of 8 mm and 10 mm were used for drilling. Hole surface roughness was investigated at the hole entry and hole exit. While revealing the surface quality change at the hole entry-exit, the effect of the drill feature difference on the surface quality has been tried to be determined. In general, hole surface quality decreased with increasing drill bit diameter when drilling both materials. The lowest surface roughness values were obtained in the use of TiN coated drill bits. Drill bit wear was also measured in the study, and it was seen that the drill bit wear increased with increasing drill bit diameter. The least drill bit wear value was also observed in TiN coated drill bits.

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