# Points to Establish Maximum Inscribed Diameter

[weisusu]

Hell All: I am going to conduct a Gage R&R study on CMM touch probe machine (software is PC-DIMS). The feature that will be measured is maximum inscribed diameter, which is tricky depending on the spots on the circle where the points are obtained. How do you determine a sufficient/adequate number of points to establish a maximum inscribed diameter so that I won't flunk the Gage R&R study?

 

[dingy2]

First of all, an R & R study compares the Repeatability of the same person measuring the same part 2 or 3 times. It doesn't make any difference about the number of points but it does make a difference on the consistency of each of the points.

The second "R" is repeatability. I hope that there are at least 2 Operators measuring the same parts two or three time and, hopefully, the same points.

Usually one uses 10 parts, measured either 2X or 3X by the same Operator and either 2 or 3 different Operators.

Anytime one is measuring a diameter, the higher the number of points, the more confident one is in the results. Make sure that you are over 12 points to achieve a reasonable value.

Dave D.

http://www.qmsi.ca