We started Shaft University as an introductory journey into golf shafts focused on a single question. “What is involved in creating a golf shaft?” From there, we explored the topics of materials, design, and production, which brings us to the end of this design cycle – testing.

As a trusted colleague likes to say, “The proof of the pudding is in the eating.” Whether a shaft design results in a physical product that achieves the target objectives isn’t clear until the shaft is tested. Or, think of it this way – everything is theoretical until it isn’t.

In a sense, shaft testing is the seminal moment when a product either checks all of the boxes, or it doesn’t. This isn’t to suggest that every shaft manufacturer uses the same checklist or maintains identical spec tolerances. However, leading brands produce higher quality products more often and more consistently.


With that, welcome to Testing 101, the final component of this edition of Shaft U. Particularly with high-performance (and high dollar) shafts, engineers are likely to argue that of all the steps, testing might be the most critical one.

Quick note – Most of the topics we address in this article apply information and terminology from the previous four “Shaft U” articles. If you start feeling a little lost or your eyes start to glaze over, grab a Diet Coke and sift through the articles that explain materials, design, and production.


In this session, we’ll cover the steps and procedures shaft manufacturers employ to ensure the performance and quality of products before factories get involved with production.

When a company like Fujikura owns the facilities where its shafts are designed, tested, and produced, it’s reasonable to assert that this gives it more control over the entire process. The same is true for companies like Mitsubishi Chemical and Graphite Design.

For Fujikura, the three specific steps of testing are:

  • Prototype Specification Checks
  • ENSO and Prototype Player Testing
  • Proprietary Durability Machinery Development

The best brands in the industry all use some form of these three steps, though they vary a bit based on available technology and processes.

Side note: Over the last several years, several DTC (Direct-to-Consumer) ball companies have provided consumers an alternative to the more recognizable names and market leaders. These brands don’t own or control the entire ball manufacturing process. As a result, the range of quality from so-called DTC brands can vary significantly. The same is true in the shaft industry.

As with any process where a 3rd party is involved, or some piece of the supply chain is exported, the OEM loses some control over the final product. Often, it’s a factory overseas performing durability and QA (quality assurance) tests.

The extent of the testing at these factories isn’t uniform, but as a general rule, it is less extensive and precise.

Fujkura Motore X Shaft

Prototype Specification Checks

It is 2020 after all, so it’s not shocking that manufacturers have the ability to create digital prototypes. Still, it’s pretty cool. Effectively, creating multiple digital prototypes reduces the need to create as many physical prototypes.

In general, working in a digital space is more time and cost-efficient. Think of it kind of like the transition from film to digital photography. It also helps eliminate some guesswork. Again, it’s worth noting that leading companies often use proprietary software to aid in this process.

Once a physical prototype exists, the raw shaft (before it’s sanded or painted) is tested and checked for design intent and to verify measurements such as:

  • Balance Point
  • Outer Diameter
  • Tip and Butt Flex
  • CPM (cycles per minute, ultimately flex)
  • Torque

From here, the shaft is sanded and retested. The purpose of sanding is twofold. It prepares the shaft for the application of paint/graphics, and it removes any inconsistencies. In doing so, it also replicates the actual production process.

Next, technicians apply paint and decals, both of which are tested for durability and repeatability. Some common assessments include:

  • Crosshatch Test – A painted shaft is scraped in multiple locations in a crosshatch pattern to ensure the paint adheres properly.
  • Rub Test – This is just as it sounds. The paint finish is rubbed against various materials to check for durability.
  • Chemical resistance Test – Acetone is rubbed on the painted to make sure the paint is resistant to outside agents.
  • Feasibility Test – A process to ensure that the specific paint color and/decal adhesion can be replicated in a mass-production setting.

The prototype shafts then go through a series of player tests and undergo mechanical testing to evaluate the strength and endurance of the shaft. For Fujikura, its ENSO® system plays a critical role alongside more standardized strength tests such as:

  • 3-point bend tests in multiple locations
  • Tip bend
  • Twist to failure
  • The Rack – endurance testing

We’ll dive into these more in the Propriety Durability Machinery Development section below.

ENSO and Prototype Player Testing

ENSO is a unique tool. There are only three ENSO systems in existence, two of which belong to Fujikura. The other one is located at PING headquarters in Phoenix.

Here’s your two-minute ENSO primer.

ENSO is a 3D motion capture camera system used for R&D and fitting. Fujikura developed the system in 2013 to better understand the relationship between the shaft and the golfer throughout the entire golf swing.

ENSO utilizes ten high-speed motion capture cameras (2,000 fps) that track strategically placed sensors. The sensors are the same as those used in CGI animation for box office films. Three cameras track multiple sensors that are affixed to the shaft and clubhead throughout the golf swing.

The system allows engineers to see how the shaft bends, deflects, and twists. It also provides insight as to how the shaft affects the clubhead.

According to Fujikura, “ENSO eliminates the guesswork of shaft design and allows it to design with tangible data.”

At a very basic level, ENSO allows Fujikura to design shafts more specifically around a desired performance metric. Basically, ENSO quantifies how an individuals’ swing impacts a shaft and vice versa.

Because it assesses the relationship between swing-shaft-clubhead, the resulting data applies to both amateurs and professionals who want to understand how a certain shaft may influence impact location and shot patterns.

Does this mean ENSO could theoretically help produce shafts as individualized as someone’s fingerprint? While that might seem like an extreme application, extracting connections between shaft properties and performance has immediate benefit as a fitting tool – and who knows, perhaps bespoke, custom, one-off golf shafts might not be as far off as one might think.

To clarify and bring a measure of brevity to all of this, the primary club performance attributes that ENSO measures are:

  • Club performance during a swing pre and post-impact
  • Shaft deflection and twist during the swing
  • Clubhead alignment at impact
  • Clubhead performance based on shaft movement

Why should I care about these metrics?

It’s pretty common to think about a shaft and how it impacts typical metrics like clubhead and ball speed, angle of attack, spin rate, and distance. It’s easy to focus on the outcomes because golf is such a results-oriented game. However, the relationship between the golfer the entire club starts as soon as the golfer initiates the backswing – and it doesn’t stop until the golfer completes the through-swing.

Compiling this data produces a bank of information that helps Fujikura design shafts it believes are most likely to benefit the largest percentage of target golfers.

Player Testing

Ultimately, humans swing golf clubs, not machines. As such, player testing is a vital component of shaft testing. Depending on the target audience, shaft companies will leverage tour staff, and other ad hoc groups made-up of trusted advisors and others inside the industry, as well as players of varying abilities and swing characteristics.

In general, shaft companies keep player testing protocols in-house, and those protocols vary from shaft to shaft depending on the intended end user – swing speeds, tempo, launch, etc..

As expected, player testing tends to center around performance, feel, durability, and playability. Launch monitor technology (Foresight/Trackman) helps companies quantify and put numbers around each player’s perceptions and experiences. It also allows manufacturers to test and see how their products stand up to shafts from competing companies.

Typically, the last step before the factory gets a green-light start production is a final durability check. After all, if there’s one thing a shaft absolutely shouldn’t do is break. At least not more than about 0.1% of the time.

Proprietary Durability Machinery

Every company designs to a particular spec, and every manufacturer has tolerances. No company makes a perfect product 100% of the time. That said, the most reliable companies tend to dedicate more resources throughout the process to help ensure a more consistent final product.

Here are some examples of machines and processes used by Fujikura to test the durability of each shaft it produces.

Torque to Failure Machine:

You have to love a machine that does exactly what the name suggests it should. With that, this machine clamps the shaft at both ends and twists the shaft in different directions to simulate the load during the swing and at impact.

As the name suggests, it pushes the shaft until it fails. To be clear, the load the machine places on the shaft is well beyond the capabilities of any typical golfer, professionals included. As a bonus, this machine can also read the torsional stiffness at different locations along the shaft.

The Rack “Torture” Machine:

Maybe the name is slightly hyperbolic, or perhaps too macabre for some. But again, it does exactly what you think it does. The patented machine simulates years of use in less than 20 minutes. As evidenced in the video, it takes the shaft and places it in a tip adapter, similar to what you’d find on pretty much every adjustable driver on the market. From there, the shaft is rotated up to 1680 rpm and then bent using 250 in-lbs of pressure.

Compared to an air-cannon test, “The Rack” is more efficient and yields more consistent results. In an air-cannon test, a cannon fires balls at various speeds and impact locations on the clubface. However, it can take 8-10 hours of air-cannon testing to get similar results compared to what The Rack can do in roughly the time it takes to watch an episode of a Schitt’s Creek.

Several equipment manufacturers use the same machine to test equipment, which provides an industry quasi-standard for durability. Also, it’s the key piece of testing responsible for Fujikura’s less than 0.10% return rate.

EI Profiling

Golf shafts are often classified by launch and spin. It’s not an inaccurate assessment, but it is an oversimplification. The same is true of CPM (cycles-per-minute) measurements, which only measure how stiff a shaft is in a specific section. But really, EI is where it’s at.

An uncut shaft is 1168 millimeters in length. Its EI profile is a graphical depiction of a shafts’ characteristics (e.g., bend profile) over that entire length. More specifically, EI is the bending stiffness that determines tip flex, midsection flex, butt flex, and frequency measurements.

Frequency measurements are like character traits. EI profiles are like DNA code.

Even given the granular level of shaft analysis, there isn’t uniform agreement on how exactly to measure the EI profile of a shaft. Cool Clubs – a company with which MyGolfSpy collaborates on shaft testing – uses a proprietary S3 system to create a database of shaft profiles. Fujikura has its platform, and the same is true for other custom fitting enterprises and shaft companies. Any repository of shaft EI profiles generally includes shafts from multiple vendors and competitors.

So, just like pretty much every other industry, each company tries to know as much as possible about as many products on the market as is feasible – and always those of direct competitors.

And there you have it. Deep breath. The next step is to work with the supply chain on a production schedule, iron out all of the details for a retail release…and then start all over again.

There’s no doubt this series probably provided some clarity for you, but hopefully, it inspired some questions as well. As always, we want to dig a little deeper and welcome any thoughts or questions you might have.

With that, here are a few questions you might consider the next time you are in a fitting or planning to purchase an aftermarket shaft:

  • “Where was the shaft engineered?”
  • “How was the shaft tested?”
  • “Who is responsible for the different stages of production?”

Ask away. The answers might surprise you.

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