I have 2 circles that I scanned. I drew a line between the 2 and that is being used as my Datum. Can runout be measured using a line drawn between to circles? I was told that using cones makes it nearly impossible to get good runout data.
if these circles are 2 locations on a shaft for example, I construct a line using 2 circles to define the part axis then use it as a datum to check concentricity or runout of other features against, I think this is what he means
yes you can use two circles to level to, for establishing a datum axis.
Measurement of runout is not relative to the axis line however, it is measured as a circumferential "total indicator readout" of the part surface.
yes the total variation of the surface while rotated about that axis line, the axis is just the datum not the runout itself. Move the axis and the runout value changes though so it is not really as independent of center point as a circularity measurement is, but yes the error is on the surface in both cases
I was working on some rotor parts. My datum A was the center of the part, a line from one end of the part to the other. (Had to use centers to check the runout as there were chamfers or cones on either side of the rotor). The measurement was a runout callout.
