开云体育

That is a edge finder. Mostly used on a mill. There are YouTube videos on how to use it. Basically, you mount it in your quill or chuck. Spin around 1000 rpm. When the small end of the part touches the edge, it will kick out a bit where the spring holds the two parts together. You now know where the edge of your part is after compensating for the tip diameter. If this is imperial size, that small tip should be 0.200" diameter. That mean you are 0.100" away from the edge. Do both sides of the part. Divide by 2, you will have the center of your part.
Al