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**General Mach Discussion / find a circle centre and radius from three points on a arc - How?**

« **on:**May 10, 2007, 08:30:47 AM »

Wizards now seem to be appearing that will find the centre and radius of a circle from three points on a arc. Can anyone help with the maths for this so that I can create the appropriate G code.

Is it possible to produce a modified centre finder in the shape of a sword, whereby the tips of the handles touch the arc at a fixed distance apart and the top of the handle slides to touch the arc. A datum line at centre of the sword then gives a reading of the radius and hence you have the centre and radius. A depth micrometer could possibly be modified. I do need the maths to try this though as I presume that the scale will be non-linear.

John

Is it possible to produce a modified centre finder in the shape of a sword, whereby the tips of the handles touch the arc at a fixed distance apart and the top of the handle slides to touch the arc. A datum line at centre of the sword then gives a reading of the radius and hence you have the centre and radius. A depth micrometer could possibly be modified. I do need the maths to try this though as I presume that the scale will be non-linear.

John