Want To Know More Information On Shaft Flexes & Tip Size?

One practice I have heard from a few fellow clubmakers which has been troubling me is the installation of 0.335” shafts into 0.370” hybrid clubheads, so I decided to conduct a little research myself. Last week I wrote about the use of brass shims to use a shaft of smaller dimension into a larger hosel opening. So that may spare you with one question you may have – how would you install a 0.335” shaft into a 0.370” bore in the first place? Now, if you are begging the question “Why?” read on.

Brass Shims #JSSHIM $.80 each

I asked that same question to these clubmakers and overwhelming their response was to hit the ball higher. Well I said there are other ways to hit the ball higher like search for a weaker lofted and/or a lower center of gravity hybrid or look at the shaft side and select one that has a more flexible tip (or one described as a lower kick point or high launching shaft). I have been writing about shaft fitting for over 20 years now and have explained that the difference between a high and low shaft kick point is nominal and the difference in trajectory will likely be 2º or less in actual launch angle when all else is the same. So if you want to hit the ball noticeably higher is may take the combination of the two and more of an emphasis on the head.

Shaft diameter effects tip stiffness
Shaft geometry plays an important role in the stiffness and the stiffness distribution of the shaft. One of the reasons why you don’t see much of a trajectory change when you compare a driver shaft to another driver shaft or iron shaft to iron shaft is the tip diameter differs little if any. What usually alters ball trajectory is the length of the parallel tip section, stiffness, material selection or material lay up (the latter two applies when discussing composite shafts).

A smaller diameter like 0.335” is not going to resist bending as much as another shaft of the shaft length, same material, material layup, parallel tip section and weight as the same shaft with a 0.370” tip. On paper I can see that reducing tip diameter significantly could in fact increase tip flexibility and that may cause a higher launch angle.

Shaft flex
Here is a fact shaft manufacturers don’t design the flex of their 0.335” or 0.350” wood shafts for heavier heads.
The flex of a club is not only directly related to the head weight and length of the club, but the flex of the raw, uncut shaft and how much (if any) tip trimming is performed. If you don’t believe me look at the trimming instructions for wood or fairway wood shafts. Typically manufacturers will stop their incremental tip trimming after the 7 wood (or sometimes a 5 wood) if tip trimmed at all.

Consider this many 7-woods on the market today weigh 228g or less. However many #3 hybrids on the market that replace a 7-wood in terms of distance weigh more. If you factor in 4, 5 and #6 hybrids, they can weigh considerably much more than that. In fact the heavier the head weight is going to make the shaft more flexible even at the shorter length without the ability to offset this by additional tip trimming.

Tale of two diameters
I decided to use a couple of shafts that I had used well in the past that I also had lying around – one of which had a 0.335” tip (wood) and 0.370” (iron). These were the Apollo Acculite 80 graphite R-flex shafts that were just recently retired. They were chosen as the separation of flex was pretty typical between the matching wood and iron version and the shaft were very symmetrical being filament wound. I also had a couple of the Caiman X2 #3 hybrids at my disposal which had the exact same specifications to install onto these two shafts.

Apollo Acculite 80 Graphite #APGAC80 $9.95 each
Power Play Caiman X2 Hybrid – Clubhead #IW1009 $22.95 each

The Caiman X2 hybrids require (or I should say designed for) a 0.370” hybrid or iron shaft. Our hybrids, with the exception of the Power Play System Q, all weigh the same as the corresponding iron number so using a shaft designed for an iron and not necessarily a hybrid-specific shaft will usually work quite well. Using my drill chuck on the raw, uncut 40” shaft, the frequency was 314 cpm. This is a good habit for clubmakers to keep good notes like I did. The instructions called for ½” tip trimming and I wanted to make the final length 40” as I usually use a little longer club anyway. With the Karma White Velvet Midsize grip I ended up with a final frequency of 271 cpm at a D3 swingweight.

Power Play System Q Hybrid Iron – Clubhead #I358 $22.95 each
Karma White Velvet Midsize #RF98 $1.99 each

Clubmakers are in uncharted waters using a 0.335” wood shaft into a 0.370” head unless that head happened to be some of the 0.370” driver heads that existed back in the 1990’s like the King Cobra TI or Orlimar Trimetal. In those cases, the weight of the driver is pretty much a standard so all you are doing is shoring up the difference with a shim or adapter.

In my case the head weighed 242g, far beyond that of a 7 wood but the instructions for tip trimming ended after 2” even though there was ample parallel tip section to trim more. Most clubmakers are going to follow the trimming instruction to a tee so only 2” was taken off the tip to see what would happen.

Using my drill chuck on the raw, uncut 46” shaft, the frequency was 240 cpm. Tip trimming the 2” and cutting the overall club down to 40” to match the other hybrid, the final frequency was 249 cpm at a D3 swingweight with the same grip. To put that in layman’s terms, the 22 cpm was basically 2 flexes less than the stated flex or L-flex even though I had used an R-flex shaft to begin with.

The ferrule dilemma
What happens when you use a ferrule designed for a 0.335” shaft onto a hybrid designed for a 0.370” shaft? I can tell you it will be undersized by a lot and it won’t look pretty or professional either. The only solution is to use a ferrule for an iron which the base of it will match up with the top of the hosel. As you can guess the ferrule will slide up and down the shaft unless you were to shim it with something like masking tape and then make sure epoxy gets underneath the ferrule to secure it in place.

Range results
The acid test to see what kind of difference there was by using the same shaft in two different tip diameters was to head to the range and find out first hand. I started with the 0.370” shaft in the Caiman X2 hybrid as this was the control club.

The hybrid with the iron shaft performed well producing nice solid shots that went straight. It comes as no surprise since I had used that shaft well in the past. On the other hand I couldn’t say the same with the same club with the wood shaft as it only produced wicked slices and fades. I even went back and forth to make sure the swing wasn’t off but the only time I could hit the hybrid with the wood shaft reasonably straight was when I slowed it down to a crawl.

On the positive side, the ball flight was indeed much, much higher. But that was a direct result of having a wide open face at impact just like opening up the face of a wedge to create more dynamic loft. As is, I could not in good faith give that club to my worst enemy to play.

Back to the workshop
Maybe the wicked slice came from a club two flexes too soft and nothing to do with the smaller tip size and subsequent flexible tip section. So I decided to retry the experiment, but this time using the S-flex version of the shaft and tip trim more to nail down the target frequency.

I heated up the hosel of the Caiman X2 hybrid and used my graphite shaft puller just in case I wanted to attempt the same experience but in a draw biased hybrid. Plus I needed a head with the exact same specifications. In pulling the clubhead, I was able to reuse the brass shim from the previous installation.

One again I wanted to document the procedure starting with the raw frequency of the shaft. With my 205g drill chuck attached on the raw, uncut 46” S-flex shaft, the frequency analyzer recorded 254 cpm. If I wanted the frequency with this shaft to match the 271 cpm as the club that performed well, I would have to tip trim more off of the tip than the instructions called for.

My raw shaft was already 14 cpm more than the R-flex version, but I still needed and additional 8 cpm. Luckily there was 5” of parallel tip section which is much more than the majority of today’s wood shafts. After some tinkering around I was able to duplicate the length, swingweight and frequency. I ended up tip trimming 3” from the S-flex wood shaft to obtain the same frequency of the R-flex iron shaft.

Range results (part two)
Now I had two clubs with the same loft, lie, face angle, head weight, grip, length, swingweight and frequency. The only real difference were subtle changes to the shaft weight with the wood shaft being about 6g lighter due to all the extra material cut off the extended length shaft, plus the wood shaft exhibited a much softer tip section and higher torque as a result of the smaller diameter tip section. In essence I was able to isolate my test down to the difference between tip stiffness.

By choosing the S-flex wood shaft and trimming more than what the tables called for made a big difference in ball flight – no more wicked slices. I alternated hitting 3 balls which each club. After about a half a large bucket of balls were struck and scattered across the range, I had a hard time drawing a real conclusion on which one went straighter, higher or farther on a consistent basis. The iron shaft felt more stable while the wood shaft had a little more feel and if there was one tendency the misses tended to be more of a pull shot. I will tell you this it was an awful lot of work for little benefit.

I plucked another golfer off the range to test the two clubs without his knowledge of what we were testing for. That is the great thing about golfers at the range – they will try anything you hand them. In his case he preferred the softer tipped shaft as it didn’t require as much force to propel the ball. Even though the frequency analyzer measured them the same, they didn’t have the same feel or stiffness. The ball flight might have been a smidgeon higher (would have needed the launch monitor to detect it) and the ball seemed to go farther for him.

What is the conclusion?
The moral of the story is it all comes down to shaft selection. I am sure if we looked hard enough, we could have found another shaft of the same weight and stiffness as the iron model used, but with a softer tip section and a higher torque to essentially do the same thing we did by going to the 0.335” wood shaft. Secondly, if you use a 0.370” tip diameter when choosing a certain shaft for a .370” hybrid it makes the assembly much easier otherwise you will have to be creative in flex selection and tip trimming to achieve your desired final flex. Most customers aren’t going to want to chop up a bunch of expensive graphite shaft shafts until they achieve their final result they wanted if they had the right equipment to do so in the first place.

Another consideration is liability. As a clubmaker you are liable for anything you build or repair. By using a shim in order to use a 0.335” shaft into a 0.370” hosel, you have more likelihood something could come loose rather than using the proper sized shaft.

If you are the club manufacturer, that is another situation. You control the stock shaft you put into a particular product rather than having a gamut of shafts to choose from probably after trying a multitude of samples and getting the opinion of your target market. This goes the same for a component supplier who might make a particular shaft strictly for a clubhead series that has been battle tested and put through all the rigors to make sure the head and shaft combination worked as designed. Plus the manufacturer will control to hosel diameter to accept the smaller tipped shaft.

Hopefully you gained a little more insight into flex distribution, especially if you had curiosity to try it yourself.

4 comments

  1. Rod Clemmons says:

    The experiment revealed that someone with a slow swing speed might like the feel of a .335 shaft in a hybrid better than the .370, even though real performance might differ very little. Since the .335 shaft is typically lighter, this might be a way to reduce the overall weight of the club for the weaker player?

  2. Jeff Summitt says:

    Rod:

    Actually the player I plucked off of the range was a pretty average to borderline stronger-than-average golfer. I think we could look at not only more flexible tipped shafts, but lighter models too as now you are finding hybrid and iron shafts down in the 50g range now.

  3. Gary says:

    Very interesting Jeff. I appreciate all the work you put into this experiment. For now, I will continue putting .370 shafts into heads with .370 holes and .335 shafts into heads with .335 holes. How about an “after market” variable length putter shaft for belly putters?

  4. Jeff Summitt says:

    Gary:

    Your suggestion has been in the work for at least 6 months now. Latest roadblock is USGA rules unless you guy don’t care whether it conforms or not.

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