What is the peak at 240 Hz in FFT in external plain turning of shaft when accelerometer placed on tool holder?

I get a peak at 240 Hz in FFT plot of tool vibration. The accelerometr is placed at 45 mm from tool tip during machining. Turning of nickel steel of dia 60 mm and length 300 mm at spindle speed...

21 June 2022 6,578 3 View