Center Aligning Cones

These are designed to reasonably accurately centre parts under the spindle of a Mill, Drill or possibly even the in the 4 jaw chuck on a lathe when you have a part with a circular hole or bore that needs truing up or enlarging.
You will also need M8 bolt, threaded rod or similar to mount in your chuck.
To use, install a bolt through the centre on the cone and hold the bolt in the chuck or collet. You can then lower the cone onto the circular hole on the face of the part you want to machine to align it with the centre of the spindle. By applying only moderate force on the spindle to keep it in place you can then clamp down your part with its centre now reasonably accurately aligned with the spindle.
I suspect you could use it with a 4 jaw chuck when you are boring out a hole also.
Obviously not as accurate as a dial gauge but perfectly sufficient for a number of applications.