Abstract: The present study is an experimental study on the effects of sharp and worn tools on the vibration frequency of the tool in turning operation. For this purpose, two forms of cutting were used that is orthogonal (knife edge tools) and oblique cutting (Vee shaped tools) conditions with varying rake angles and tool overhang. Machining test cuts were conducted on a CNC lathe machine (Okuma LH35-N) without coolant for different depth of cut. In addition, the work piece material was mild steel and the cutting tool was made of high speed steel (HSS). Flank wear and vibration signals were measured by surface texture and accelerometer instruments, respectively. The experimental results show that, the majority of the sensitive portion of the spectrum to sharp and worn conditions is within the frequency range of 0 to 3.5 kHz such that worn tools may be detected by increasing the spectrum amplitude. Also it was found that the proposed detection method is robust against changing of the rake angle and tool overhang conditions within the specified range.