This Equates to a Hypotenuse, at a 45 Degree Angle, of 0.007 (Radius) Times 2 = .014 True Position RFS.
Not Considering the Tolerance for the MMC, the 0.002 MMC, would be a severe and dramatic reduction of the total tolerance.
0.002 True Position is…[Read more]
The General Rule of Thumb is +/- 25% of the Sample Size.
Example: Average Sample Size of 100 +/- 25% = +/-25, it is OK to use the same Control Limits.
If the Sample Size is <=74, or >=126, then use Different Control Limits.
These different control limits are sometimes referred to as a Manhattan Skyline.
If you have a negative CPk, it means you have at least 50% Failures, assuming the formula is correct.
The lower the negative CPk, the more Percent failures.
As an Example; Negative 1 CPk would be about 99.7% Failures, to the Specification
I would like to provide some additional insight.
1.) Assure that the Gage is Acceptable for the measurements.
1.1) Check Increments and Resolution, Gage Resolution should be less than 10% Resolution, I recommend 5%.
Example: +/- .010 = Total Tolerance of .020. Increments to be less than .001 = 5% Resolution.