I wanted to add a little to the explanation related to the frequency charts. A few years ago Jim and I created some charts that showed the actual shaft flex ranges that you get within any flex designation. Part of what is below comes from an explanation Jim gave to someone asking about the differences in Frequency Charts.
Basically, we have two different frequency charts. The GLFMC chart I mentioned before that we include with our Maltby Laser Frequency Machine (MA2014), which is for testing assembled clubs with the grips installed.
https://www.golfworks.com/pad-of-frequency-charts/p/glfmc/ These would also work with the Auditor Frequency Machine because both machines have a 5” clamp.
The other Frequency Charts on the web site with the colored areas are the ones for checking assembled ungripped clubs. As I mentioned before, we believe the correct way to test clubs for frequency is to test them ungripped. With these charts we listed ranges for shaft flex because there is no one frequency line that will work for all R flex or S flexes etc. Even with this colored chart there are shafts that will test outside the ranges. You can see some examples at this link from our web site with some of the shaft sets we tested. https://www.golfworks.com/iron-frequency-chart-examples/a/1656/ You will also see from this chart that not all shafts follow the same frequency slope. These charts are also based on a 5” clamp.
If you do an internet search you will find a lot of different frequency charts. The reality is there never has been and never will be a chart that will work with every shaft on the market. It is just not possible. We feel we did a good job with our colored charts using flex ranges as oppose to a single line. You would basically need a separate frequency chart that has the stiffnesses reference and slope for each different shaft model on the market.
Hope this information helps with the explanation on Frequency.
Britt Lindsey / Jim Yachinich