Sorting Through the Confusion of Golf Shafts

Let us face it – shaft fitting can be quite confusing. Even for those who are immersed in shafts all day long have a tough time communicating with potential customers. For example, try to have someone explain the difference between a $30 graphite shaft and a $300 graphite shaft in terms of performance. Or it is the lingo you constantly hear like low torque, high modulus, frequency, medium launch angle, low spin, among others.

The common guy will just shake his head and say, “Just give me the one I can hit as long and straight as possible and be within my price range.” Even the experienced golfer with enough information to be dangerous wants it explained into plain language which is easy to digest.

diagram of confusing shaft terms on the golf industrydiagram of confusing shaft terms on the golf industry

The 5 Roles of the Golf Shaft

Let us look at the role of the shaft for a second. When you look at the modern shaft in the lowest common denominator, it is really a tapered hollow tube. Think about that for a second. Now ask a myriad of people about the importance of the shaft and you will get just as many varied answers. There will some out there that will say the shaft does little, if anything, and it all comes down to the swing. Then there are others who believe the shaft is the engine or transmission of the club and the most important of all the components. This might come as a surprise and a shock to some, but I fall somewhere in-between.

Provide Feedback to the Golfer

I will insist that the shaft is more than just a “thing” to connect the head to a grip. Imagine if we have no shaft at all. Perhaps you have a Nintendo Wii at home. Golf is one of the games you can play if you are not familiar with the Wii. While it is fun to play on a snowy afternoon, there is one element that is dearly missing. It is the “feel” aspect of the game.

diagram head, shaft and grip and completed club, text The shaft is more of a thing to connect the head to the grip"diagram head, shaft and grip and completed club, text The shaft is more of a thing to connect the head to the grip"

Use your imagination for a second. Let us say we had the technology to incorporate an electromagnet inside the grip to keep the club head a constant distance from the hands. If you were to swing the club and hit the ball, what would happen? The ball might fly as it should, but on impact you would not have any feeling or feedback of where you hit on the face if you ever did. You see, the shaft acts as a transmission device to allow the feedback from the clubhead to hands and then up to your brain.

Before I go any further, I want you all to consider this. Let us say you are currently hitting a 45.75” right handed driver with some sort of 55g shaft in R-flex as that is the most popular combination today. If we just re-shafted the club with 120g steel shaft or sub-40g graphite shaft at the same length, you would still be able to hit the ball. If you changed the shaft from, say as flexible as the most flexible ladies flex shaft all the way to the stiffest extra stiff shaft, you could still hit the ball. The shaft may be less than $10 or cost well over $300 and you could still hit the ball.

So how important is shaft fitting when you can change any of these parameters and still hit the ball? Well, this leads us to the rest of the roles of the shaft.

Providing Sufficient Weight

Aside from the length of a driver, what is the first thing we notice when you pick up the club? Well, it is the weight. Since head weights from one manufacturer to another do not deviate that much, then the overall weight of the club is primarily controlled by the weight of the shaft.

We already stated golfers are most concerned with performance and could care less about the details. Shaft weight should be one of the first considerations after you have established what length club you need. The reason the shaft needs the right amount of weight is to be able to swing the club most efficiently. Most people assume that a lighter weight shaft can be swung faster and provide more distance. Well, that is not always the case. A shaft that is too light, the player ends up playing what I call “Zorro golf” and has no idea where the club is during the swing. If the club is too heavy, then it is difficult to swing the club efficiently.

Every person reacts to weight differently so there is no magic formula. Where you or your customer maximizes distance on the bell curve will need to be evaluated with various weight shafts or at least pay close attention to which shaft weight has worked well in the past and avoid shaft weights that have not provided satisfactory results or have shown a lack of efficiency.

weight distribution chart with bell curve of driver shaft weight and distanceweight distribution chart with bell curve of driver shaft weight and distance

Provide Balance

I should also point out it is not always the weight of the shaft, but the balance point or weight distribution of the shaft that matters too. This is where the importance of swingweighting comes into play, but the shaft’s weight distribution can contribute to the swing efficiency as well. Look at the diagram for a second. The white dot on the shaft denotes where the balance point of the shaft is.

Shafts that are tip heavy may make the club feel heavier or have the same effect as a heavier weight shaft, while a shaft whose weight is concentrated closer to the butt end can give the same sensation as using a lighter weight shaft. Therefore, another role of the shaft is to provide some sort of balance or weight distribution in conjunction with the shaft weight.

diagram of two clubs being balanced with one possessing a golf shaft with a higher balance point for a lighter feeldiagram of two clubs being balanced with one possessing a golf shaft with a higher balance point for a lighter feel

Provide Feel Plus Control

There also needs to be some semblance of feel and control. What I mean by that is golfers covet the concept of feel. Years ago, there was a shaft company called Fiber-Speed. They offered extremely flexible shafts, some which were far more flexible than what is currently on the market today. You could get a lot of whip and feel – even for golfer who had slower speeds.  The problem was for golfers that were stronger or had more of an aggressive swing and had no idea where the ball might land.

On the other side of the spectrum was Ping. For years, their irons came with X-flex and then later S-flex shafts. That was the only option despite the fact whether you were a strong swinging pro, average golfer, senior male or even a lady – you got the same flex shaft. The idea was that the stiffer shaft provided control. However, the feel component was missing from the equation. Over time Ping started offering multiple flexes for their clubs.

I strongly believe there needs to be a compromise between having a shaft that provides for a nice soft feel, but with adequate control. Again, each golfer will have their own interpretation of what feels good. 

Despite what some might say, hitting a club with a softer or stiffer shaft than what is optimal for a golfer is not going to cause huge disparities in distance as you might think (direction and height perhaps). A player’s swing speed and solidness of contact control the distance with all thing else being the same. But it is the feeling caused by the flexibility or lack of flexibility that creates the timing aspect in the swing, which provides the control and the confidence the golfer has in the club.

diagram of average fairway width a tight and a wider landing zone areadiagram of average fairway width a tight and a wider landing zone area

You or your customer maximizes control when you do not have any thoughts about the feel or flexibility of the shaft in the back of their mind where subconsciously you are adjusting. Just like weight, selecting the proper flex for both control and feel needs assessed with various shafts or at least pay close attention to which shaft flexes have worked well in the past and avoid shafts with similar parameters which caused undesirable results.

Feel can be measured in other manners beside just the flexibility of the shaft. Golfers that suffer from joint, hand or other related discomfort from hitting balls might consider graphite shafts – if they are not too light, and the walls are not too thin to dampen vibration as much as a thicker walled shaft. Most golfers however consider graphite shafts for weight savings. 

But in recent years you see graphite iron shafts that weigh the same as most steel shafts. And now you might find steel shafts (at least in the irons) that are as light as many graphite models. There have been steel shafts that had inserts pre-installed inside the shaft to dampen shock.

No matter how well a golfer hits a club, if it does not feel good, they are less likely to use it. Conversely, no matter how good the feel, if they cannot control where your ball lands, they will not be using that club long either. That is why one needs the right amount of balance between the two.

Change Ball Trajectory

Lastly, there is one more role of the shaft and that is to allow for some change in the trajectory through the stiffness distribution and/or the balance point of the shaft. 

Just like the type of ball you use or the loft and center of gravity of the head, the shaft can influence the trajectory and the spin of the ball, although it has minor role. We will touch upon this more when we start looking at each of the individual shaft and clubhead parameters.

diagram of 3 ball flights plotting trajectories and distancesdiagram of 3 ball flights plotting trajectories and distances

Traditional Shaft Fitting Methods

For years, shaft fitting was and still is primarily based on how fast you swing the club or how far you hit the ball. In some cases, it may be based on ball speed with the accessibility of launch monitors. But distances can be misleading since many golfers well…exaggerate just how far they hit the ball, or the golfer does not make solid contact with the ball to get an accurate correlation to the speed that a better ball striker can provide. But at least it is a starting point.

Shaft flexes are presented in a generic nomenclature. For example, L or Ladies flex is the most flexible of the five flexes and traditionally designed for golfers with driver swing speeds of 60 mph or less. A-flex or what is also referred to as Senior or Amateur and where the A is derived from, is geared for driver swing speeds between 60-75 mph.

R or regular flex is for the average male golfer whose driver speed is between 75 and 90 mph. S or stiff flex is designed for golfers with a faster swing speed, usually between 90 and 110 mph. The stiffest of the golf club shafts is X or extra stiff and designed for those who can swing their drivers above 110 mph.

diagram of a tachometer but showing swing speed with shaft flexdiagram of a tachometer but showing swing speed with shaft flex

While these make good generalities for shaft fitting, it is nowhere exact for a couple of reasons. After from spending the past 35 years measuring thousands of shafts that have been available to clubmakers and fitters, I can say that there is no standardization when it comes to shaft flex.

Determing Shaft Flex by Deflection

Flex is determined usually by one of two ways today. First is deflection, which is one of the oldest forms of flex measurement. It starts by clamping the butt end of the shaft and applying a known weight to the tip end of the shaft or the assembled club.

The clubmaker simply measures the amount the tip deflects downward with the weight compared to without. The more deflection that occurs – the more flexible the shaft is at the same given length. A deflection board may use a 6 or 7 pound weight to bend the shaft from the butt end. If the shaft is reversed to measure tip deflection, then a lesser amount of weight is required and an effective way of determining relative flex.

measuring flex of a golf shaft by hanging a heavy weight at the tip endmeasuring flex of a golf shaft by hanging a heavy weight at the tip end

Determining Shaft Flex by Frequency

A more common way for clubmakers to measure flex today is with the use of a frequency analyzer. The frequency analyzer is used to measure the stiffness of a completed club or even the raw shaft. In either case, the butt end is securely clamped into the analyzer. Then the head or tip weight of the shaft is “plucked” and set in oscillation. The higher the number of oscillations (at the same given length), the stiffer the club or shaft is said to be.

measuring the flex of a golf club in a frequency analyzermeasuring the flex of a golf club in a frequency analyzer

There are few frequency analyzer options on the market and not all will measure the same. The reason is some analyzers may clamp 2.5,” 3.5,” 4”, 5” or 7” of the shaft or club and some clamp with or without a grip. In each case you will get a different measurement. The key is making sure that all clubs or shafts are measured the same way each time, so you have data that you can compare on an apples-to-apples basis.

The following chart is based upon the measurements of hundreds of assembled drivers and 5-irons with different shafts that are available today. This chart considers the recommended tip trimming by the manufacturers, the differences in the raw lengths of the shaft as well as the swing weights. 

Average Assembled Club Frequency

Driver Steel Shaft Graphite Shaft #5 Iron Steel Shaft Graphite Shaft
L Flex 236 229 L Flex 286 264
A Flex 243 234 A Flex 288 268
R Flex 252 246 R Flex 301 281
S Flex 263 258 S Flex 314 292
X Flex 270 271 X Flex 323 304

All L-flexes measured for Driver and 5-iron, C-6 swingweight
All A, R, S & X flexes measured for Driver and 5-iron, D-1 swingweight
All measurements using a 5” clamp with each club gripped


The concept I want you to take away from this chart is that first and foremost, the difference on average between adjacent flexes is not always a constant, but it is approximately 10 cpms between flexes. This has been the accepted difference within the industry.

Secondly, the frequencies of steel and graphite shafts on average are not the same with the same letter designations. These two shaft materials should be treated separately or as apples and oranges. 

Next, averages are calculated with the highest and lowest readings and everything in-between. The difference in assembled club frequency of identical flex, lengths and swingweights can be quite considerable. If you do not believe me, just look at this next chart.

Assembled Club Frequency Ranges (Steel Shafts)

  Drivers 5 Irons
Flex Low High Deviation Low High Deviation
L 227 255 28 269 321 52
A 232 268 36 270 301 31
R 233 275 42 257 334 77
S 243 281 38 271 337 66
X 259 284 25 307 335 28



Assembled Club Frequency Ranges (Graphite)

  Drivers 5 Irons
Flex Low High Deviation Low High Deviation
L 204 272 68 227 313 86
A 219 267 48 239 303 64
R 225 277 52 260 320 60
S 226 298 72 267 348 81
X 246 309 63 269 347 78


Remember what I stated earlier that 10 cpm is generally considered one full flex. Just look at the L-flex graphite range that I have highlighted. Incredibly there is a 86 cpm range in what two shafts from different manufacturers designed as an L-flex shaft at the same given length. This would represent over a 8 flex range if 10 cpm is considered one full flex. And remember that there are only 5 flexes!!!

I should clarify this part and state this chart is the culmination of all the shafts I have tested over the years and not just what’s available today. With the consolidation in the golf industry and fewer shaft manufacturers, you will not see anywhere near this wide of a range. There is no standardization on the part of the manufacturers, so there will be a variation from one manufacturer to another and even within their own product lines. Part of the explanation as to why these ranges exist, is that this helps to create unique shafts as there are many different philosophies on shaft design. If not, we would all be playing the same shaft.

As you can see from a frequency standpoint there is flex overlap. Potentially, an X-flex shaft  by one manufacture may have been more flexible than an L-flex shaft by another manufacturer. In the end, the generic letter designation tells us little about the true flex of the shaft.

There is another reason the flex of shafts is not all the same and that comes down to the weight of the shaft. One should really compare one shaft to another in with the same weight range and material. This diagram shows you the relationship between the cut weights of S-flex steel 5-irons. I remember years ago when the first ultra-lightweight steel shafts came on the market. In attempt to make them the same stiffness as the heavier shafts, they always felt “boardy” and unresponsive. But over the years, the amount of flex in a design has been more performance-driven than trying to target a specific frequency number. 

The more successful lightweight steel shafts have become progressively more flexible, or I should say possess a lower frequency as they become lighter and lighter. A 75g steel shafts may appear on paper to be 2 or 3 flexes softer than their heavier brethren. But put into play without any preconceived notions and they perform as the flex letter designation would indicate.

graph charting frequency versus shaft weight for S flex 5-ironsgraph charting frequency versus shaft weight for S flex 5-irons

Stiffness Distribution

I mentioned earlier that one of the roles of the shaft was to provide trajectory change. This is often occurs by the geometry of the shaft and why you see different step patterns and parallel tip length on steel shafts or graphite shafts constructed from various materials and laid up at various angles not to mention differing rates of taper from tip to butt. 

Since the butt end is larger than the tip end, it only makes sense that the maximum point of bending on a shaft will be located below the mid-section of the shafts.

There are three different tests to measure the bend profile of a shaft or at least the point of maximum bending. For years, bend point was a method used to describe how the shaft might launch the ball. The assumption was the higher the bend points the lower the ball flight.

Shaft Bend Point

To measure bend point, the shaft is clamped at both ends and compressed. The maximum point of bending was the bend point. 

technical diagram of measuring the bend point of a golf shafttechnical diagram of measuring the bend point of a golf shaft

Shaft Kick Point

Measuring for kick point is slightly different. The butt end is clamped, as if you were holding the grip end and a force or load is applied to the tip. If you drew a straight line from those two points, the position where the maximum deviation occurred is called the kick point.

technical diagram of measuring the kick point of a golf shafttechnical diagram of measuring the kick point of a golf shaft

It should be noted the point of maximum bending, whether it the bend point or kick point test is in the same no matter what the force, only the amplitude or amount of curvature changes. So, shafts are said to have multiple bend or kick points depending upon how hard you swing is impossible. Plus, the point of maximum bending is in a narrow range; not the wide range some may be led to believe.

Bend point and kick point have been defined in the past by:

                1.            High bend or kick point has a firm tip and flexible butt section

                2.            A low bend or kick point has a weak tip and firm butt section       

                3.            Mid bend or kick point falls somewhere in-between

Just like the flex of the shaft, there is no universal testing method adopted by golf industry. Plus, there is overlap from what one shaft from a manufacturer might call low bend or kick point to what another manufacturer might call mid. Lastly the measurements are typically only conducted on the raw, uncut shafts – so what happens when the shaft is cut?

In reality, graphite shaft designers can make the butt stiff, tip stiff and the middle section weaker and it wouldn’t fall into any of these categories. This is all possible by applying materials in specific locations and at different angles on the shaft forming mandrel.

E.I. Curves

Shaft manufacturers and R&D labs are now using E.I. (elasticity times inertia) Curves, or a three-point bending test that measures the load or the stiffness distribution of golf shaft more accurately from tip to butt. This data is fed into a computer and plotted to replicate the deflection curve. Shafts could then be analyzed side-by-side for comparison purposes and launch conditions correlated to robot data.

defecting a golf shaft with an EI shaft profilerdefecting a golf shaft with an EI shaft profiler

This chart shows the deflection amounts along the length (every 2”) of four different cut 5-iron shafts from the tip (left) to the butt (right) end all using an EI shaft profiler. All of these had the exact frequency, yet they were quite different in their stiffness distribution. The higher the reading (deflection) on the chart illustrates a more flexible portion of the shaft.

comparing 5 different Graphite Design shafts for stiffness distribution that all had the same frequencycomparing 5 different Graphite Design shafts for stiffness distribution that all had the same frequency

Today companies will indicate the trajectory relative to other shafts within their own line based on launch monitor and/or robot data, which is a far better system, but still does not accurately compare shafts from multiple manufacturers. 

Even so, humans swing shafts often with unique swings – like fingerprints. The position where the unloading of the shaft takes place in relationship to the impact with the ball as well as how far rearward the center of gravity of the head is - controls the trajectory and even face angle more so than a single maximum point of bending that occurs on the shaft.

Shaft Torque

The term torque is a measure of resistance to twist. Technically it is the wrong terminology, but those within the golf industry have used it so long, that is simply what we refer to it as. Torque is one the most understood of the shaft terms. Most assume that low torque is better and that is not always the case. The right amount can help square up the face of the club at impact as well as contribute to the positive “feel” of the shaft.

Golf shaft torque is measured by usually clamping the butt and applying a force of 1 foot-pound to the tip and record how many degrees of twist that occurred. That is all it is. Once again there is no universal method of measuring adopted by the manufacturers. Some manufacturers will clamp more of the tip than others so there is no way of looking at manufacturer’s published data and confidently comparing it to another manufacturer torque listings. 

technical diagram showing how shaft torque is measuredtechnical diagram showing how shaft torque is measured

I should also say torque does exist in steel, but it cannot be independently changed like graphite shafts can. The weight and stiffness primarily control what the torque of a steel shaft will be and the reason you do not see it listed by the manufacturer or that information is missing in component supplier’s catalogs or websites.

Years ago, I was designing one of Hireko’s house brand graphite shafts using an existing model. We had substituted two layers of longitudinal layers, which control the flex, for two layers of bias ply material to reduce the torque. We also selected a higher modulus material, or a fancy term for high strength, to compensate for the lack of stiffness by changing the fiber orientation.

When we looked closely at the two models, the weight, flex, and geometry of the shafts were identical. The only thing we did was alter the torque and a couple of layers with different materials which completely changed the trajectory, performance and even the feel between the two shafts. One other thing it did was also increases the price of the shaft. 

As you can see this is why there are so many different shafts to choose from as simple alterations like this can give shaft designers an endless array of potential products. This leads us to the next part and that is to figure out what shaft you or your customers need.

Summary: 4 Basic Shaft Fitting Parameters

Let us look at the four basic shaft parameters. We have the flex, stiffness distribution, torque (at least on graphite shafts) and the weight of the shaft to choose from. The only parameter we may be able to confidently fit is weight as all the other parameters have absolutely no universal method of comparing one shaft to another because of the lack of standardization.

Flex (Generic letters – L, A, R, S & X)                        Subjective and NO uniformity of testing

Stiffness distribution (High, Mid, Low)                    Subjective and NO uniformity of testing

Torque (Measured in degrees)                                 NO uniformity of testing

Weight (Measured in grams or ounces)                  Finally, something everyone agrees upon!

Accurate Shaft Fitting Requires Accurate Data

So, this is where I come in. For the last 30+ years I have been testing shafts using the same testing equipment and testing methods. By now this has covered @ 50 different shaft manufacturers and nearly 4000 shafts.

We have compiled these into two books. The first publication is the Modern Guide to Shaft Fitting. This book explains why we started testing shafts, goes in-depth on each of the shaft parameters and then explains our results. The second book called the Shaft Fitting Addendum had been updated annually until the past few years. It has all the data or numbers of the cut shafts as a means of comparison. 

I want you to first understand that accurate shaft fitting requires accurate data. I cannot over-emphasis this part enough. What we have attempted to do is the legwork for you as we have tested all these shafts so you can truly compare one shaft to another.  With the average graphite shaft trending toward the $100 range, you or your customer do not want to make an expensive mistake. However, if you have the means of testing shafts and keeping records, you can do the same thing.

We spent years and continue to this day, studying why certain shafts work well for some golfers and why they do not with others. So, we created an index or a way to rank shafts in order of their stiffness and we call this the Dynamic Shaft Fitting Index or DSFI for short. 

Finally, and most importantly, we produced a relatively simple system that club fitters could use the data to fit their customers. The reason this system had been successfully used by clubmakers and fitters alike for three decades is the DSFI is based on the actual cut data we accumulated. This data includes the final club frequency, cut torque, tip, and butt deflections as well as length and then put into an algorithm. The DSFI system is unbiased as we are only concerned with the data points.

I will tell you this, club fitters should be more concerned with selecting a shaft that is going to fit their customer instead of selling what we have most in stock or providing the greatest profit. This is how you continue to maintain your customer base.

Getting Started in Shaft Fitting

Measure Swing Speed

For shaft fitting, obtaining a swing speed with a driver or mid-iron is our starting point. Manufacturers might suggest a swing speed range (as much as 10-15 mph) for each of their shafts and there are reasons for that.

Detrmine Length of Golf Swing

One factor is the length of a golfer’s swing. I want you to look at the diagram for a second, look at the hand position of the two golfers. On the right, the golfer is taking the club back parallel to the ground. We will call this a full swing as the hands reach the top of the swing and there is a wrist cock to get the club in that position.

technical diagram of a golfer with a 3/4 swing versus a full swingtechnical diagram of a golfer with a 3/4 swing versus a full swing

Over on the left side, the golfer has more of a ¾ swing or short of being parallel. That is the hands are between waist high and at the top of the swing like the golfer to the right. You may have heard of this as a “laid off” position. 

Unless you are a swing instructor, we really do not care how the club is swung. We are only trying to identify certain traits. There have been many golfers over all these years with unique swings that have managed to play this game well.

Clubhead speed or velocity is typically measured in mph but could very easily be converted to feet per second. To make things easier to understand, let us say both golfers had a constant velocity of 85 mph or 125 feet per second.

In this diagram we are going to say it illustrates two golfers using a 45” driver. The golfer on the left with the ¾ swing might have that clubhead travel a total distance of 8.13 feet from the top of the back swing until impact. The golfer on the right taking the club to parallel might see the clubhead travel a total distance of 12.19 feet from the top of the back swing until impact. These are approximations to help state our point.

I am sure you realize the elapsed time of a golf swing is short. For most golfers it is in the 0.9 to 1.3 second range and there have been devices on the market over the years to measure this. However, it rarely breaks this down into the back swing and down swing components. The back swing may take 0.8 second to 1 second leaving the down swing or the part of the swing we are most concerned with somewhere just below 0.2 seconds to a little more than 0.3 seconds. Does not sound like much difference, does it?

Let me put this in perspective. If these two golfers both have the same velocity, then it will take a shorter amount of time for the golfer on the left to go from the start of the back swing until impact. In this case, the golfer on the left may complete the down swing in two tenths of a second and the golfer on the right may take twenty-nine hundredths of a second to complete the downswing until impact.

We spoke earlier about the frequency of a shaft. If we look at the average frequency chart, an average A-flex driver might oscillate 234 cycles per minute. 234 cpm is also 3.9 cycles per second (divided by 60 to convert minutes to seconds). To complete one full cycle, it would take a little over ¼ of a second or 0.256 seconds. Again, there is no secret how I produced that as all I did was divide the number 1 by 3.9 to show the time to complete one full cycle.

If a shaft oscillates 255 cpm like an S-flex shaft in a driver, it can be converted to 4.25 cycles per second. If you divide 1 by 4.25 you end up with 0.235 seconds or the time it takes for one full cycle to complete. This is the reason why a stiffer shaft is suggested for a golfer who takes less time to complete the down swing even though the speed at impact is the same. This is why we suggest a stiffer shaft for a golfer with a ¾ swing than their swing speed would suggest.

Let me add one quick note about swing speed. From swing to swing and even day to day, our swing speed can fluctuate. That is another reason a golfer should have a swing speed range rather than relying strictly on the golfer’s average swing speed. Secondly, shafts have a manufacturing tolerance that by luck of the draw could end up slightly stiffer or more flexible from one to the next or from batch to batch.

Determine Golfer’s Tempo

In our next diagram, we want to further explain why swing speed alone is not always the best determinate for shaft flex. I am sure you have heard of the term tempo. It really refers to the rate of acceleration, which is the relationship of velocity over time. A golfer definitively does not possess constant acceleration throughout their swing.

technical diagram illustrating a fast, moderate and slow swing tempotechnical diagram illustrating a fast, moderate and slow swing tempo

If you look closely, notice the curved arrow in black. This represents the area of peak acceleration in the swing. The illustration on the far left shows were peak acceleration occurs early on in the swing and what I will refer to as a fast tempo. That is the time to go from the start of the down swing where the initial velocity is zero until peak acceleration occurs quickly.

For starters, the shaft would be subjected to a tremendous amount of deflection or bowing from the golfer pulling the club down from the top of the swing so abruptly (some may say loading the shaft). To compensate for the greater amount of deflection that will occur, the shaft should be stiffer to counter this effect. 

Some of you may also refer to this as an early release where the golfer is trying to hit the ball with force starting at the top of the swing. In fact, the shaft is basically on cruise control as it comes into the impact zone. I have heard people say that the shaft flex will not matter if the release occurs early in the swing, but it has been my experience that a shaft that is too flexible will throw off the person’s timing and rhythm. Again, one of the roles of the shaft is to provide feel and control.

Shaft Fitting Examples

Let us use an example of a golfer with a 100mph swing speed and a fast tempo and ¾ swing. By scouring the manufacturer’s websites or product literature, you find 3 potential shafts of the 4 below that fit your customer’s swing speed. But which would be the best choice?

Model Swing Speed Range
Shaft #1 85-95 mph
Shaft #2 90-100 mph
Shaft #3 95-105 mph
Shaft #4 100-110 mph

As we mentioned previously, the ¾ swing would need a stiffer shaft than their swing speed would indicate. How much? You could add another three to eight percentage increase to their swing speed or 103-108 mph to compensate for the abbreviated speed. In this case, the “Shaft #4” would be the best candidate.

If the player possessed a 100 mph swing speed with a fast tempo and a full swing, then that player would need a shaft within +/- 3% of their swing speed for a comfortable range to allow for day-to-day fluctuations in their speed. In this case, they would be better off selecting “Shaft #3”

In the middle diagram we have labeled as moderate tempo, the dark gray arrow shows a gradual build up speed. The black arrow shows the area of peak acceleration which occurs later in the swing when the wrists un-cock. Then prior to impact the shaft starts to decelerate. This is common among golfers, but the release point will vary.

Because of the gradual build-up of speed verses the rapid acceleration caused by the fast tempo, the shaft will not have near as much deflection, at least in the upper portion of the swing. Therefore, we feel that the shaft does not have to be as stiff as the golfer with the faster tempo and the same swing speed. Let me reiterate that again. 

With the same swing speed, the golfer with the moderate tempo (and full swing) should be able to use a slightly more flexible shaft. By how much. A reasonable amount is by three to eight percent lower or between 92-97 mph range. . In this case, the “Shaft #2” would be the best candidate.

In the diagram on the right labeled slow tempo, the golfer loads or deflects the shaft the least at the top portion of the swing. Some might consider this a late release or when the wrist releases right before the impact with the golf ball.

But think about this for a second, if the golfer has a very late release, then the peak velocity is at or very close to impact.  The person with a fast tempo who reached impact at the same speed has a higher velocity somewhere else in the swing.

The slow tempo golfer (with a full swing) should be able to use a shaft even more flexible (and potentially lighter) than the moderate tempo golfer and still maintain control. Our DSFI system, we suggested between 8-13% lower or to look for a shaft that was rated close to an 88-92 mph range or in this case, the “Shaft #1” that you may never had thought of before.

As a recap, here are the adjustments to their swing speed to find an appropriate swing speed range.

Player's Swing Speed Multiply By 3/4 Swing 1.03 - 1.08
Fast Tempo, Full Swing 0.97 - 1.03
Moderate Tempo, Full Swing 0.92 - 0.97
Slow Tempo, Full Swing 0.87 - 0.92

Narrowing Down Shaft Choices


Once we have found an appropriate swing speed range based upon the golfer’s swing speed, length of swing and tempo, we may find several shafts to choose from. Our first consideration (or I should say customer’s) is cost. Individual shafts can range from just over $6 to $400 or more. Be certain to select the best shaft choice that is within the customer’s budget. If they cannot afford then it doesn't matter how good the shaft is.


Remember the fundamental rules of fitting. Whenever a golfer has a quick tempo, opt for a heavier weight shaft in whatever material you are seeking. For slow tempo golfers, they are candidates for using lighter weight shafts. The length of the swing arc can also play importance in the proper shaft weight. The longer the golfer’s swing arc, potentially they could use a lighter weight shaft, while a shorter golf swing may need a heavier weight shaft for added control.

Trajectory and Flight Bias

Next sort the shafts based on the manufacturer’s trajectory description (such as high flight, mid-flight, or low flight). There may be variations of these like mid-to-low or mid-to-high, but regardless this may help optimize the launch angle and create the desired feel by the player. Typically, the more flexible the tip, subsequently a higher launch angle may occur. Another thing we have found is a shaft with a softer tip section produces a draw bias or assists in allowing the clubface to close. Shafts with a stiffer tip section as well as low torque could be considered fade biased or assist those who tend to hook the ball.


You might see (at least with graphite shafts) a range of torque values. If the golfer has a slow(er) swing tempo, you might select a shaft with a lower frequency / lower torque combination within the selected range of shafts. If the golfer has a faster swing tempo, then opt for a shaft with a higher frequency / higher torque relationship within the selected range of shafts. The stiffer shaft will stabilize the clubhead, while the higher torque will typically offset the stiff feel.

Other considerations

By now, you might have already chosen an appropriate shaft. However, you might find certain shafts from one manufacturer that is like another manufacturer. A popular type of shaft is bound to breed competition. The player may want a shaft to color coordinate with the head, grip, or golf bag. Believe me, I have heard it all. Brand name loyalty helps generate sales or it’s the manufacturer’s warranty that is the driving factor that might sway you one way or another between two shafts that on paper look very similar.

Performance Based Shaft Fitting

There are some club fitters who do not use club head speed to fit shafts at all. They use performance based fitting, which is to have their customer demo different type shafts – different weights, different stiffness, different stiffness distribution, different torques, etc. until that find a shaft that works well for the golfer. Just think of an ophthalmologist or eye doctor by asking the question “Is A better than B?”  Instead of an array of lenses to choose from, the club fitter will have an interchangeable head and shaft fitting program.

Remember, the customers only care they hit the club well. They do not want to be concerned or confused by all the technical terms. You are the professional and they rely on your expertise to fit them correctly. 

Performance based fitting may very well be the best way to fit, but it will take longer as the customer may get tired, and the testing may have to be repeated to really nail down the right shaft. For the fitter it can be very expensive to offer a wide array of shafts that could conceivably fit each golfer that walks into their shop. That is why they need to be smart and make sure that they do not have shafts that duplicate one another.

Shaft Demos

A club fitter may select from between one or three shaft manufacturer’s lines. Here is an example of a basic matrix of driver shaft options to use in your demo clubs. By choosing one shaft you are assured you are not duplicating your efforts. You might select higher launching shafts at the low end of your range and mid or lower launching shaft at the high end of the swing speed ranges.


Driver Swing Speed Range
<70 mph 70-80 mph 80-90 mph 90-100 mph 100-110 mph
40-49 g        
50-59 g 50-59 g 50-59 g 50-59 g  
  60-69 g 60-69 g 60-69 g 60-69 g
      70-79 g 70-79 g
Higher Launch ------------------------------------Lower Launch


By offering one iron shaft in each of these categories you will be sure not to duplicate. By adding additional models in selected swing speed ranges (based on driver speed), make sure the weights are different enough and the ball flight description by the manufacturer is not the same. Again, it will not take long to build up your demo program but at least this way it forces you to think it through.

Iron Shafts by Shaft Material
  <70 mph 70-80 mph 80-90 mph 90-100 mph 100-110 mph
Steel     X X X
Graphite X X X X  

Creating Alternative Shaft Flexes

You may find from time to time that a customer is caught between two flexes. There is a way to remedy this situation called the principles of soft and hard stepping shafts. This is probably not something that is commonly taught or you might not have heard of this process before. But the concept is a way of altering shaft flex. 

These terms mostly apply to taper tip steel iron shafts, but the concept can also be applied to parallel tip shafts in general as I will explain a little later. I should give you a little background on taper tip shafts first. For one, the entire component industry works exclusively with parallel tip shafts, so when we talk about taper tip steel shafts it will come up only in retrofitting of an existing name brand's pro-line iron sets or wedges. 

Taper Tip Shafts

Taper tip steel shafts come in various lengths with each length designated for a different head. The only example that did not was the Apollo Hump due to its unique geometric profile. One of the first things you should know is that each shaft pattern has various suggested lengths, and those lengths are not the same from one shaft pattern to another. Plus, some shafts are designed for 1 and 2 irons which do not exist anymore. Lastly, in certain patterns, the wedge shaft is the same as the 9-iron and in other sets it is shorter.

The tip to first step dimension on each raw length is the major reason the flex is built into the shaft. This dimension is proportionally shorter by 1/2” as each shaft decreases in length almost as if it were pre-trimmed by the manufacturer. The beauty of this is that is saves on one additional step in the assembly process, which is the tip is trimmed. 

This diagram shows what a typical set may look like when you buy them. In this case we start out with a 40” raw length for the 3 iron and goes down to 36 1/2” for the wedges. As I said before, each length is suggested by the manufacturer so this would be the length you would normally order for the True Temper GS85 or 95 shafts. A Dynamic Gold or a KBS Tour may require totally different lengths for the same 3 through PW.

diagram of tip to first dimensions and raw shaft lengths for a set of taper tip iron shaftsdiagram of tip to first dimensions and raw shaft lengths for a set of taper tip iron shafts

If you look from the butt end down to the first step, the shaft will look identical. It is the tip section that determines the flex. Now the negative aspect of taper tip shafts is this requires the clubmaker to carry a greater amount stock keeping items than you would in most parallel or I should say unitized tips shafts. Therefore, taper tip shafts are geared more for mass produced pro-line OEM clubs. You will not see them in boxed sets or in some of the manufacturer's game improvement models.

Soft Stepping Golf Shafts

Soft stepping refers to the assembly practice of choosing a longer than normal raw length taper tip shaft for the clubhead than suggested by the manufacturer. It is for the purpose of achieving a stiffness that is more flexible than what the shaft has been designed to be. 

It is also a term describing the practice of trimming less from the tip than required in the shaft installation process for the purpose of achieving a stiffness that is more flexible than what the shaft has been designed to be. I will get into that in a little bit.

As we mentioned before, taper tip shafts receive no tip trimming at all, but require the clubmaker to purchase a specific raw length for each head. For example, if we wanted a taper tipped shaft for a 3-iron, we would normally select the 40” raw length for the Dynamic Gold.


  Dynamic Gold
Club # Recommended Raw Length Soft Stepped Once Soft Stepped Twice
1 iron 41"    
2 iron 40.5" 41"  
3 iron 40" 40.5" 41"
4 iron 39.5" 40" 40.5"
5 iron 39" 39.5" 40"
6 iron 38.5" 39" 39.5"
7 iron 38" 38.5" 39"
8 iron 37.5" 38" 38.5"
9 Iron 37" 37.5" 38"
PW 37" 37" 37.5"
SW 37" 37" 37"


If we wanted to soft step the shaft once, we might take the shaft for the 2-iron or the 40.5” raw length in the Dynamic Gold pattern and place that in the 3-iron. What this will do is make the club more flexible because the tip to first step length is ½” longer than the 40” version. 

The extra 1/2” will be removed when we butt trim the shaft. It is important to remember the butt diameter is larger than the tip end making it stiffer. By adding more to the tip section and reducing the length of the butt makes the shaft more flexible.

By soft stepping once, this will make the club about 3 cpm lower in frequency. In some shaft patterns it may be as much as 4. If we soft stepped two lengths or used the 41” shaft which is suggested for the 1-iron and put it in the 3 iron, this would make the club approximately 6-8 cpm lower than using the recommended shaft length. Most in the industry regard 10 cycles per minute as a whole flex. So, you can see what magnitude the effect of soft stepping has on the final flex.

You might be trying to match shaft flex amongst different patterns of shafts. A Dynamic Gold S300 might be the equivalent of a Rifle 5.8.  By soft stepping once, you will achieve something closer to a 5.5 flex and soft stepping twice will approximate a 5.2 flex. On the wedges, you could elect to use the same raw length as the 9-iron or make them progressive for greater control like shown in the table.

Hard Stepping Golf Shafts

Hard stepping is the opposite. It refers to the assembly practice of choosing a shorter than normal raw length taper tip shaft for the clubhead than suggested by the manufacturer, for the purpose of achieving a flex that is stiffer than what the shaft has been designed to be. It can also be a term describing the practice of trimming more from the tip than is required in the shaft installation process for the purpose of creating a stiffer shaft than what the shaft has been designed to be.

  Dynamic Gold
Club # Reccomended Raw Length S300 Hard-stepped once X100 Soft-stepped twice
1 iron 41" 40.5"  
2 iron 40.5" 40"  
3 iron 40" 39.5"  
4 iron 39.5" 39"  
5 iron 39" 38.5"  
6 iron 38.5" 38"  
7 iron 38" 37.5"  
8 iron 37.5" 37"  
9 iron 37" 37" 38"
PW 37" 37" 38"
SW 37" 37" 38"


By hard stepping, you would choose a shorter raw length shaft to make the club stiffer. We might take the shaft for the 4-iron or the 39.5” raw length in Dynamic Gold and place that in the 3-iron making it 3 cpm stiffer. One word of caution regarding hard stepping, it will be difficult to do for a full set because you are going to run out of raw lengths.

Look at those entries as indicated in light shade of blue. In this case, you will not have the additional stiffness you need in your most important clubs. That does not happen generally when soft stepping as most golfers never carries a 1 or 2 iron. But in hard stepping it does. However, there can be a solution.

If these were Dynamic Gold S300's hard stepped once, you might be able to take Dynamic Gold X100 and soft step twice for the 9 iron and wedges to try to match the set up.

Parallel Tip Shafts

These same principles apply to unitized parallel tip shafts or a master shaft that is designed to be used for a complete set of irons or woods. Just because the trimming charts say you need to trim a certain amount from the tip, does not mean you have to.

You should already be familiar with the term parallel tip. It is where the tip is made to be one constant diameter up to a certain point on the shaft. Parallel tip diameters are typically .335" and .350" for woods, and .370" and for irons. Unitized is a term you may have not heard of. It describes shafts in which one shaft can be used to build a complete set of irons and one shaft can be used to build a full set of woods through successive trimming of the parallel tip section. Unitized shafts allow for a decrease in the clubmaker's inventory of raw length shafts when building a set of clubs.

The two terms are not interchangeable though. For example, parallel tip True Temper GS-85 and 95 shafts (which are no longer available). The parallel versions all had dedicated lengths to allow for their constant weight design. In these cases, these can be soft or hard stepped as we outlined in the taper tip shafts.

There is another option. Being parallel tip, you could elect to tip trim the shafts additionally as there would be adequate parallel tip length to do so and still allow the shaft to bottom out in the bore of the club. Plus, the shafts are long enough you are trimming off at least an inch from the butt on standard length clubs. If you tip trimmed 1/2” off each of the raw lengths that would be essentially the same as hard stepping once.  Tip trim 1” more would be like hard-stepping twice. But whatever you do, be consistent throughout the set. Secondly, as a clubmaker, you have the ability to cut to in-between flexes in cases where a person may fall in-between two flexes or create additional flexes that do not exist.

For example, let us look at the Apollo Phantom R/S combination flex iron shaft. This shaft can be either cut to either a regular or stiff flex by following the recommended trim charts by the manufacturer. Here is a chart showing what the manufacturer recommends for R-flex in gray and S-flex in black.

Apollo Phantom Tip Trimming
Flex 2 iron 3 iron 4 iron 5 iron 6 iron 7 iron 8 iron 9 iron Wedge
Soft R     0" 0.5" 1" 1.5" 2" 2.5" 2.5"
R 0" 0.5" 1" 1.5" 2" 2.5" 3" 3.5" 3.5"
Firm 1" 1.5" 2" 2.5" 3" 3.5" 4" 4.5" 4.5"
S 2" 2.5" 3" 3.5" 4" 4.5" 5" 5.5" 5.5"
Tour S 3" 3.5" 4" 4.5" 5" 5.5" 6" 6.5" 6.5"
X Tip Trim to Length


You will notice that there is a 2” difference in the tip trimming between these two flexes. If we cut the shafts to each of the two flexes in identical heads, lengths and swingweights we would see a 10 cpm difference. However, let us say we wanted to make the shaft between R and S flex or what may be called a firm flex. We can tip trim 1” more than chart for the R-flex or 1” less than S-flex chart. We would have confidence that a 1” difference in tip trimming would result in a 5 cpm change.

As a clubmaker you can create even more flexes by just applying the principles of soft and hard-stepping. The shaft has nearly 10” of parallel tip section so we have plenty of room to trim more if we wanted to create a stiffer flex or hit a target frequency.  And since fewer and fewer customers are carrying 3 and 4 irons, you can create softer flexes by trimming less.

Apollo Phantom Frequency
Flex  2 iron 3 iron 4 iron 5 iron 6 iron 7 iron 8 iron 9 iron PW
Soft R     276 280 284 289 293 297 302
R 272 276 281 285 289 294 298 302 307
Firm 277 281 285 290 294 299 303 307 312
Tour S 282 286 290 295 299 304 308 312 317
X 287 291 295 300 304 309 313 317 322


Even though the manufacturer may have stated this was a combo R&S shaft, we created five flexes out of one shaft. Just understand the limitation you have regarding parallel tip length and overall shaft length. You may have to work out on paper ahead of time if you can create the desired flex, you, or your customer needs.

What is a Spine on a Graphite Shaft and Why Should You Care?

This topic may be more prevalent in our companion clubmaking book but does enter the club fitting picture because not all shafts of the same kind will feel or perform alike due to manufacturing tolerances. A “spine” (sometimes referred to a spline) is an imbalance or inconsistency created during the manufacturing process of a graphite shaft. Let us show this phenomenon in diagrams so it is easier to understand.

Important note: Finding the spine on a shaft or where it exhibits FLO by rotating a shaft into a frequency analyzer or shaft clamp is not to be confused with PUREd shafts or the SST PURE technology. This is a patented process to find the most stable orientation using a proprietary device. This process is only available through a network of licensees.

How is a Graphite Shaft Constructed?

 There are two primary techniques used: sheet-wrapping and filament winding. Sheet wrapping is by far the most common method of composite shaft manufacturing today. In the sheet wrapping process, pennant-shaped sheets of pre-preg graphite (known as flags) are wrapped around a forming mandrel. The various flags of pre-preg can be wrapped one by one around the mandrel or can be compressed together on a forming table and then wrapped all in one procedure around the mandrel. After wrapping, the layers are then compressed tightly around the mandrel to eliminate as many air pockets or voids between layers as possible. Depending upon individual design, as little as five layers of composite material up to thirty layers may be used in the manufacture of a single shaft.

During the filament winding process, multiple series of continuous strands consisting of blended graphite materials are coated with a binding resin and machine wound around a rotating forming mandrel to produce the shaft.

Because of the continuous winding process, filament wound shafts do not have a start and stop point for layers as do the sheet wrapped type of shafts. All fibers are laid up at angles to prevent them from slipping on the mandrel and as such there are certain design limitations.

technical diagram how a filament wound golf shaft is producedtechnical diagram how a filament wound golf shaft is produced

Filament wound shafts are said to possess a higher level of uniformity in wall thickness from one shaft to the next but is not necessarily a superior method of construction as there are pros and cons with both methods.

Due to the lesser amount of consistency, we are going to target our focus on sheet-wrapped graphite shafts but note that filament winding does not devoid the possibility of some kind of spine on a shaft is possible. Another thing to be aware of is on a sheet-wrapped shaft, each layer is not all the same.

 Graphite layers, which are applied with the fibers aligned lengthwise to the shaft are what controls stiffness, while the layers that are wrapped with the fibers at an angle to the forming mandrel play the key role in determining the torque value of the shaft. Most are at 45° angles, but you can also see designs incorporating fiber at 30°. Lastly in some more advanced designs, graphite layers are wrapped perpendicular to the mandrel to increase the “hoop strength” or limit the shaft from becoming out of round during the swing, therefore providing improved shot dispersion.

technical diagram how a sheet wrapped golf shaft is producedtechnical diagram how a sheet wrapped golf shaft is produced

These wraps of pre-preg flags will not be full length around the forming mandrel. Some of which will be small lengths to reinforce certain portions of the shaft or control the stiffness distributions. The more layers, the more expensive the shaft becomes due to the labor involved.

How A Spine is Created on a Golf Shaft

Now we have a little better understanding of these layers, how exactly are they placed on the shaft? As the shaft increases in diameter from tip to butt, the flags must be carefully cut because they are wrapped around a tapered mandrel, and they need to minimize the amount of overlap.

Some overlap might be OK as the shaft will eventually be sanded during finishing. Where the problems lie as follows. Think about this for a second, once you wrap one layer of material around the mandrel, the diameter will become larger. This means that the next flag of material must be correspondingly wider, so the edges meet up when wrapped completely. If not, then you can get a gap.

technical diagram of creating an overlap when wrapping graphite shafts around a mandreltechnical diagram of creating an overlap when wrapping graphite shafts around a mandrel

In addition, the layers need to be staggered, for example, every 90 degrees so any overlap does not continue to build up and make the shaft more out of round or where one portion of the shaft wall is thicker or a so-called “spine” than the rest.

Consumers assume the shafts they receive are perfectly round and they are not due to manufacturing tolerances. Remember these are hand rolled onto the mandrel, so placement is the key. Mass-produced shafts will be more likely to see a build-up of material as the operators are focused on speed and may not be as careful making sure of the precise placement of the flags on the mandrel or making sure to stagger the layers evenly. As they say, you pay for what you get.

 The name “spine” or “spline” implies that the ridge build-up will be a straight running the length of the shafts. That is not the case in a sheet-wrapped shaft. Any overlap will occur at the same rate of the taper at that position on the mandrel. The most expensive or premium shafts are not mass produced, and the flags are more precisely cut as there are far more quality control measures in place to reduce overlap and not create a noticeable spine.

diagram with the overalled seam running at an angle on the shaftdiagram with the overalled seam running at an angle on the shaft

What Effect Does a Spine Have on Shaft Flex?

 One measure of shaft flex is the use of a frequency analyzer. By clamping the butt of the shaft and plucking the shaft with a weighted object on the tip to set it in motion, one can get the relative stiffness of a shaft (or club).

oscillating a golf shaft in a frequency analyzer with a tip weightoscillating a golf shaft in a frequency analyzer with a tip weight

In this example, the sensors pick up the oscillation of the shaft when going in the up and down motion. Another frequency analyzers may have the sensors pick up the frequency when the shaft is oscillating side to side. In the diagram, a tip weight is attached to the shaft tip rather than a head. In most cases, a tip weight has some sort of quick release mechanism like a thumb screw or the ability to twist (like a drill chuck) so it can be attached and removed quickly.

 In this diagram, we are looking directly at the end of the tip weight (drill chuck). The wonderful thing about a drill chuck compared to a golf club head is the weight distribution is even around the shaft whereas the head is not. So, if we plucked the shaft in an up and down motion, you would expect the shaft to oscillate in an up and down motion as well.

 A well balanced shaft is one where regardless of orientation the shaft would oscillate the same. This is not always the case because of manufacturing tolerances.

a well balanced golf shaft oscillates in a nice up and down motion in a frequency analyzera well balanced golf shaft oscillates in a nice up and down motion in a frequency analyzer

If a shaft has a definitive “spine,” then the shaft will want to oscillate in more of a Figure 8 pattern; some might be so severe they smack against the sensors. I call these Harvey Wall Bangers.

an unbalanced golf shaft oscillates in a figure 8 motion in a frequency analyzeran unbalanced golf shaft oscillates in a figure 8 motion in a frequency analyzer

Flat Line Oscillation

It is possible that if you have a shaft with a pronounced spine that the shaft could oscillate straight up and down. What you say?  Shafts that oscillate in figure 8’s can be loosened in the frequency analyzer, turned several degrees, tightened and then re-oscillated. For instance, if a shaft was oscillating in a figure with a noticeable patter, by rotating the shaft 90 degrees, it will oscillate in the reverse pattern. Somewhere in-between these two areas you may find two planes (positions) that the shaft will exhibit in what is referred to as a Flat Line Oscillation (FLO) or where the oscillation is straight up and down or side to side.

This is the goal for those that “spine” a shaft and can be time consuming to find the exact position. Some clubmakers may go as far as to use laser pointers on the end of the tip weight so they can see how straight they can get the shaft to oscillate rather than eye-balling it.

As we mentioned before, by turning a shaft 90 degrees, you will usually find the opposite rotation. In the case when flat line oscillation occurs, by rotating 90 degrees either way, it too should exhibit FLO. In this diagram we have found one FLO plane and the frequency with our tip weight measures 227 cycles per minute (cpm). After rotating the shaft 90 degrees we again have FLO, but this time the frequency  measures 238 cpm. The higher the number, the stiffer the shaft so the plane with 238 cpm reading is the stiff plane and the soft plane is the one with the 227 cpm reading.

frequency oscillations of a golf shaft in two planes; stiff plane and soft planefrequency oscillations of a golf shaft in two planes; stiff plane and soft plane

One interesting tidbit is when FLO has been found try rotating the shaft 45 degrees one way or another then watch the oscillation. This typically will be the worst non-linear oscillation or where you will see figure 8s. Shafts with a variation of +/- 2 cpm (or less) around the circumference of the shafts are very good. While FLO may not occur in all 360 degrees around the shaft, any wobble in the oscillation is minimal. Almost all your premium shafts will fall into this range.

Shaft Symmetry

As mentioned, shafts with a variation of +/- 2 cpm (or less) around the circumference of the shafts are very good. To put that in perspective, 10 cpm is considered a full flex so this amount would be @ 2/5ths of a flex or less. Here is the deflection profile of a shaft that showed a 3 cpm variation from the strong to the weak plane. The two deflection curves drape over one another except in all but a few areas. Chances are this shaft could be installed in any orientation into the head and have the same feel. Even though the shaft in this example is not perfect in terms of looking at the frequency around the circumference, some tolerance is acceptable if it is minimal.

deflection analysis of a shaft with a tight frequency tolerancedeflection analysis of a shaft with a tight frequency tolerance

But what happens when the tolerances are not minimal? In our previous example, the frequency between the soft and stiff plane was 11 cpm. First, you will not see steel shafts exhibit anywhere near this degree of difference in frequency as steel shafts are made of the same material throughout and for these reasons, we are not addressing it at all in this section.

 Here is another example along with a deflection curve. In this case we have a shaft with a delta in frequency of 11 cpm or a little more than a whole flex depending upon the shaft orientation. You guessed it, depending upon how this shaft is installed into the head could feel, play, or perform quite differently. This is one reason there is flex overlap or inconsistency from one shaft to the next and why two identical clubs do not always feel or play the same.

deflection analysis of a shaft with a large spine and wide frequency tolerancedeflection analysis of a shaft with a large spine and wide frequency tolerance

This part is especially important. Let us say you have taken the time to fit the player with a demo club. For starters you should have recorded the raw frequency of the shaft long before and kept good records. That way when you reorder another of the same shaft to build or retrofit into another head you will know whether there could be a potential problem with the flex and the final product when you go to hand the club to the customer.

Golf Shaft Installation

If you install a graphite shaft with the logo in the “up” position, there is no guarantee where the so-called spine is or that the shafts will FLO. In most cases it is Russian roulette, especially in lower cost, mass-produced, entry level shafts. Clubmakers may also have some sort of device in their shop to locate the shaft “spine.” While Hireko does not sell one, a spine-finding devise can be found on the Internet or plans to build one. Each type of device has its own nuance so be sure to read directions carefully.

If you have found the FLO planes and identified and more importantly marked the shaft, the next decision is how to install the shaft into the clubs. According to the Rules of Golf Appendix II (2.) Shaft (a.) Straightness, the USGA addresses this issue.

“However, many graphite shafts have a small “spine” running along the length of the shaft which may make them bend differently depending on how they are fitted to the head. As previously noted, the USGA recognizes that it is difficult for manufacturers to consistently produce a perfectly symmetrical shaft and, provided that the shaft is manufactured with the intention of meeting the above requirements, the USGA may incorporate a reasonable tolerance when evaluating shafts for conformance. Additionally, manufacturers of clubs may orient or align shafts which have spines for uniformity in assembling sets, or to make the shafts perform as if they were perfectly symmetrical. However, a shaft which has been oriented for the purpose of influencing the performance of a club, e.g., to correct wayward shots, would be contrary to the intent of this Rule.”

I remember when a patent to “spine” shafts first came out in the late 1980’s (yes, this is not new) there were provisions to orientate the shaft in such a method to help eliminate hooks or slices. This was accomplished by placing the shaft at 45 degree angles to the “spine” into the head or in our nomenclature FLO. Before you get all excited that you can cure the common slice, realize the USGA only wants the orientation in the FLO or neutral planes. Plus, golfers will still slice, and any shaft orientation may only help alleviate a bad shot at best.

 There are two positions you should install the shaft after you have found the FLO planes. There are different opinions on which is better so you may have to experiment yourself to find out which you believe works better. I prefer the first position as shown in the diagram where the stiffer plane is orientated in the 12 o’clock to 6 o’clock position into the club head’s hosel. This reduces the amount the shaft droops or flattens out in the swing.

The soft plane is now in the 3 o’clock to 9 o’clock plane or toward and away from the intended target line. This would be the same whether this was for a right or left-handed player. Conversely, some clubmakers prefer the stiffer plane to be placed in line with the target or the 3 o’clock to 9 o’clock plane.

The purpose of determining FLO and orientating the shaft into the head accordingly is to create impacts on the face that are more clustered together. That will result in straighter shots and more confidence. Realize that inexpensive entry-level shafts WILL exhibit a higher degree of inconsistency in the flex around the circumference of the shaft compared to the more expensive premium shafts. However, do not construe that as being inferior unless the shafts are installed willy-nilly. If properly spined or FLO’d, a shaft with a prominent spine can perform well for a golfer assuming it is the right weight, stiffness, and bend profile (for launch conditions).

diagram of shaft installation in the head once the spine has been identifieddiagram of shaft installation in the head once the spine has been identified

Shaft Fitting Synopsis

While shaft fitting can be confusing, it all starts with having accurate information. In the end, the customer should have a shaft that is the proper weight and balance to control their timing and tempo. The shaft’s stiffness distribution and torque should complement the club head’s loft, face angle and clubhead bias to deliver the face to a suitable position upon impact. Lastly, the shaft should provide a balanced amount of stiffness for a positive feel or feedback to the golfer. Any change in the feel of the club, due to the bending and twisting of the shaft, is going to elicit a change to the response of the golfer subconsciously. By matching the weight, stiffness, stiffness distribution and torque to the golfer’s natural swing, fewer adjustments are made by the golfer resulting in more consistency from swing to swing.

You also see how it is possible to create customized flexes for the cases where a customer is in-between flexes, or a shaft flex does not exist as in the case with A-flex taper tip steel shafts when retrofitting an existing set of irons or wedges for a customer. 

Shaft fitting is important. But it should be no more important than fitting for the right size and style grip, club head angles and the length. The golf club is a system rather than comprised of independent parameters.

Modern Guide to Golf Clubmaking

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