Re: Tol vs. Part to Part is it ndc?
This spreadsheet evaluates the guage for two very distinct purposes.
The tolerance method is calculating the P/T Ratio. This compares the gage variation to the total tolerance, and assesses the guages suitability for part inspection to tolerance. Your gauge is very suitable for part inspection.
The "Using Part to Part variation" method calculates %GRR. This compares the gauge variation to the part variation, and assesses the guages suitability for process control (e.g., SPC), or for use in statistical studies (e.g., DOE, t-tests, etc.). ndc is a related measure to %GRR. It does not relate to P/T Ratio at all. If the variation of the parts accurately represents the variation of the process, then this guage is not suitable for process control. If you need this guage for process control, you will need to reduce the repeatabilty (within operator) variation.
Most guages are used for inspection or for process control, but not usually for both. Determine what this guage is used for, select the appropriate method (P/T Ratio for inspection; %GRR for process control), then make your decision based on the result of that method. The results of the two methods will not typically match each other, so don't let that worry you.