Some lathing products such as Pistons or Pins have counterbores, and the end surfaces of counterbores are required to be flat as the upper pictures. Producing flat end surfaces needs extra machining process with extra machining tool which increases production costs.
Allowing to remain drill tip shape at the center of the end face of counterbores as the bottom picture, then extra machining is not necessary that reduces production costs.
We, E&H Precision, Asia's Largest CNC Machine Lathe Turned Part Manufacturer has more than 700 CAM CNC automatic turning machines and specialized drilling machines with internally produced drill tools in Japan, Thailand & India.
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