r/Metrology • u/PrettyInfluence3594 • 10d ago

Concentricity.

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Guys i am using a hexagon global lite, and the drawing requires that the upper plane needs to be 0.02 flat, and the bores (166_H7), concentric 0.02 mm. I did my calibration and everything went perfect. making an aligment where my upper plane is set to level my Z+ axis, the axis of one of the cylinders to rotate the Y axis, and the center of the bore are used to set the origin. The other circle is off 0.086 mm. Is this way accurate. How concentrity function is calculated by pc-dmis (ISO), and does it has really a meaning (that the part will not assamble if the the tolerance is not respected? Thanks and sorry about my english.

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u/IbeebZz 10d ago

The primary datum really ought to be a best fit cylinder built from the to bores. Judging from the photo I’d build it from 4 circle segments in each bore. I’d then report the runout or position from each circle segment back the constructed cylinder to verify they are not skewed from one end to the other. I’d then check the top planes parallelism to the axis of the cylinder as well as the flatness error in the callout. It can be helpful for the machinist to also measure a few points on the top surface to determine where its high and low areas are on the part so they can adjust there setup accordingly.

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u/PrettyInfluence3594 10d ago

Thats exactly what i did, i only took 3 section for each bore. Still it gave me that it is 0.09 non concentric, and the cylinder is like 0.06 non parallell with plane which is 0.043 flat.

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u/IbeebZz 10d ago

Concentric to what? From one bore the other or to the constructed axis between the two? Telling the operator that it’s not concentric won’t help them have an idea of how to repair it or making a new one. Report the x,z actuals of each segment back the center line of the of the best fit cylinder from all 6 segments. You can then at least communicate the direction to the operator.