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.
My part was approx 1.5feet tall and 3" in dia..had a bunch of runouts that were "G-H" on my print (the blue surfaces).
Datum -H- was kind of small so I only did two circles on it. But you get the idea.
Ray Harvey
This is pretty much what I've done on several parts and I like it, our in house engineering drawings don't use much GDT so it is up to me to define datums as I see functionally important... and I report the form deviations I want to, but it all saves our ass when assemblies fail and we need to defend our parts. Often the root cause is never really determined but those with the least inspection data are on the hook. Those 2 datum surfaces on a shaft will often be the bearing journals for example and the rest of the shaft can be checked for runout functionally the way it will be restrained by the bearings in service.
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.
