Swing Speed and Frequency Analysis

Standard Flex Designations
As we like to say in Silicon Valley, "the problem with standards is there are no standards".

Most of the confusion relates to different techniques employed to measure CPM. When Dr. Braley invented the concept of electronic calibration measured in CPM to describe relative stiffness, he also invented a machine. It was a big, heavy clunker with a clamp on one end and a stationery electric eye on the other. The clamping length was 2 7/8 ", clubs were usually tested with the grip on, and the club was oscillated in a vertical plane, usually "toe up" to prevent banging on the machine.

Over the years, competitive equipment for measuring CPM came on the market. The manufacturers focused on cheaper, modular components and more accurate technology. The butt clamp turned into a 5" clamp, the measurement was done with the grip off to narrow irregularities caused by grip textures, and the optimum oscillation plane was horizontal, or "face down the line". These differences result in readings that can vary 10-15 CPM from the Royal Precision method. That's well over a full flex difference. Consequently, a 6.0 is not necessarily a 6.0. The actual stiffness "depends" on the variables previously described.

When you discuss CPM, it is imperative to know what method was employed to find CPM in the first place. If you want to look like you know it all, you can simply ask: "3 or 5 inch clamp" and that will put your salesman on notice that you know more about frequency than you're supposed to.

The Professional Clubmakers' Society (PCS) has devised a calibration system that gives clubmakers who are "standardized on the PCS system" the opportunity to compare "apples to apples". The PCS standard is based on a 5" clamp, grip off, and horizontal oscillation. On the PCS standard, there is still no universal agreement on what the numbers mean. However, debate has narrowed the range. Consensus is developing that "Regular" is between 4.5 and 5.0. Stiff is between 5.5 and 6.0.