GRR for troque driver.

We just did one and used 5 torque wrenches of the same nominal value, 3 operators, and 3 replicates. In the GRR platform, substitute “torque wrench” for “part”. Our wrenches have a +/- 6% tolerance so we translated this to in-lbs and plugged this in as the upper minus lower in Minitab. Our R&R / Tol was horrendous. We did a what-if, and used a wider tolerance based on drawing requirements for the screws we are torquing. Even using this tolerance, the R&R/Tol was real bad. We have a new torque analyzer on order.
 

A few questions;

How did you verify the resultant torque from each of the 3 operators?
What was the range of torque values that you have them tighten to?
How did you select the 6 tools & 3 operators? 
I would set it up as follows;
Select ten torque values representative of the range used in your shop (if you torque from 1 – 10 in lbs, use 1, 2, 3, 4, 5, 6…… 10).  Select 3 operators and 3 tools.  Using a desktop torque tester, have each operator use each tool (twice) to tighten to each of the ten settings.  record the actual values from the torque tester. 
With this method, most of your variation should be part-part.  If it’s not, then I’d bet that you’d have some operator variation (applied torque would vary by how fast torque is applied, where on the shaft the driver is held, environmental conditions, etc).  If you’re seeing a lot of operator variation, I’d recommend refresher training followed by a repeat of the GR&R

Its only destructive if you’re using actual fasteners and mating surfaces.  Using a desktop torque tester allows you to avoid that.

I may be wrong, but I believe the “500” reference was to the number of torque drivers being used on the floor rather than the number of fasteners.  Mountz is a brand of drivers.

the GRR applies to the measurement system. (the torque analyzer).
It is not intended to assess the capabilities of the torque wrenches.
is the customer interested in how well you torque things, or how well you measure torque?