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A golf club fitter needs to know the properties of the shafts he is fitting you with. I first learned about shaft profiling from Tom Wishon. He assembled a database of linear shaft bend profiles using a strain gauge frequency instrument. It got my interest and I put a great deal of time into frequency profiling shafts on my own and developed a rudimentary database of my own.

During a visit to a shaft company R&D site I was introduced to the concept of EI profiling. That began my exploration of other methods of describing the properties of a golf shaft. I learned the term EI from engineers in the business of designing shafts. The instrument used was in the $10K+ range, not affordable to most. Not even all shaft companies had these instruments.

It took about 2 years to come up with an workable, affordable EI measuring design. After many years of use, I decided it was time to redesign and improve the original. I knew all the sources of error in the original design and fixed them. The machining was beyond the capacity of my mill and I had to outsource the cutting of the parts. The precision of the parts made by a machine shop further improved the instrument and made designs I could only imagine possible.

The new design far exceeded expectations. Most of the original instruments have been upgraded. A number of my instruments are now owned by shaft companies. The latest to acquire one has reported it is the fastest, easiest to use and most accurate instrument in the business. The first production run of the new instruments is nearly sold out and a second production run is commencing.

Recent promotion of hoop strength by a shaft company lead me to explore how hoop strength is measured. One method is compression testing. A tube is placed on a block and a weight is placed on it. The amount it bends under this load is a measure of hoop strength. After a few tests I designed a support and added hoop strength measurement to my instrument and database.

With a driver shaft database of 1200 shaft profiles that include stiffness, torque and hoop profiles, I and my affiliated fitters know the shaft you are being fit with. That knowledge makes us exceptional fitters. Six of the fitters using this system are on the recent Golf Digest Top 100 ClubFitters list.  To learn more about the instrument and software look at the bottom of the Products page for links.


Custom Built Clubs – Golf Shaft Set Certification

I have been using the prototype of our new version shaft EI instrument for several months. The parts are now being machined and distribution of the upgrade and the new instrument will begin in July of 2014. Much of my software is being revised.

When I custom build iron sets I document the measurements taken. Often the measurements include checking every shaft in the set. This is offered as an additional service. On occasion a shaft in a set is an outlier. It does not match the rest of the shafts in the set, or it has a weak or hard spot along its length. That shaft gets returned to the manufacturer and replaced. Without having each shaft checked, you will never know if your set is consistent. The following report is provided to document the certification and building specifications on custom built sets.


This is a study of the radial properties of 6 shafts.  It is a supplement to the golf shaft alignment video. I discussed bow vs spine in that video, and mentioned that the two did not necessarily align with each other. But the example used in the video very closely aligned with one of the FLO’s. In this larger study of 6 shafts, there are examples showing more clearly the point that was made in the video.

The charts below show the effectiveness of the Three Point bearing tool, often referred to as a spine tool and a tip weight laser tool in locating the radial stiffness high and low points of a driver shaft.  The tip laser device, often refered to as Flat Line Oscillation FLO or Vertical Oscillation Plane VOP was an effective tool for finding the stiff and weak planes of the shaft.  This can be accomplished by the club maker by FLOing the shaft in a CPM device and noting the CPM of the shaft at each of the two FLO planes.  The stiff and weak planes are easily identified.

The bearing based Spine tool is not a reliable device for identifing the stiff and weak planes of a shaft.

This study was inspried by the writing of my friend, Dave Tutelman.  This link is his article on the subject,

Four properties were measured as follows:


The stiffnes of the shaft as measured every 10 degrees.  The shaft was clamped at the butt end, the tip was deflected 1″, the load cell was set to zero.  The shaft was then deflected 5″.  This method measures the stiffness of the material without any affect from any bowing or curvature in the shaft.  The readings are shown as the blue line.  The readings were smoothed to eliminate measurement ‘noise’.

Vertical Oscilation

A weighted laser tip was attached to the shaft.  The shaft was deflected 3″ and released.  The laser trace was recorded in a 5 second timed exposure.  The shaft was rotated until a stable plane of oscillation was found.  The photo of the trace is shown to the right of the shaft.  The shaft was then turned 90 degrees and the second stable plane was located.  The solid red line shows the stable plane of the shaft closest to the stiff side of the shaft.  The dashed red line, the stable plane that was on the softer side of the shaft.


Using a three point bending tool the bow of the shaft was located.  This tool is a pair of bearings in a tube.  The shaft is inserted into the ID of the bearings and a third bearing is used to deflect the shaft.  The shaft turns to the bowed side to minimize the stress of the loading force.  The Bow is shown as a Yellow line.

Tip Deflection

The shaft was inserted into a machining chuck which can be rotated.  Two pieces of card stock were bent 90 degrees and set against each side of the tip.  The shaft was rotated.  The cardstock was pushed away from the shaft as the tip moved during the rotation.  The points of maximum deflection to the right and left were noted and indicated by the black line.



We recently updated this blog and changed our video hosting platform. I had to go through all the posts and relink the videos. This post falls into a category I must call legacy material. It was early in my discovery of EI profiling and shows version 6 of my instrument. Its crude compared to the current instrument, and so is the production. But, it has been watched thousands of times. It is on the list of productions that need a remake.

Golf Shaft Flexural Rigidity – EI Profiling

Young’s modulus is a measure of the stiffness of an elastic material.  It is often used to determine the strength of a beam.  Shaft stiffness varies along the length of the shaft.  Using Young’s modulus, the ratio of stress to strain, a shaft can be measured at different points along its length.  This has come to be known as shaft profiling.  When the values are expressed per Young’s modulus, this is called EI Profiling.  Other databases, using different methods to measure stiffness, are also used for the same purpose.  A fitter uses knowledge of the flexural profile of shafts to quickly find a shaft that fits a golfers swing.

Golf Shaft Stiffness Measurement

The flex terms one commonly sees, R, S, X have little meaning to a fitter that knows the EI profiles of the shafts he uses.  As one comes to understand the many, many shaft stiffness profiles available today, flex letters become little more than a shaft manufacturers method of swing speed rating their shafts.  There is no uniform standard for defining shaft stiffness.  And as you develop a knowledge of EI profiles, you understand the futility of thinking that a standard could be defined.  Each design will load and unload differently in the hands of different golfers.  What works for one style of swing at a particular speed will behave differently with a different swing style at the same speed.

Golf Shaft EI Measurement Instruments

When I learned about EI profiling, I discovered there was no uniform system for measuring beam stiffness of golf shafts.  Laboratory instruments used by some shaft companies, cost in excess of $10,000.  A friend and I undertook the design and creation of a EI measuring instrument.  Our objective was to use gravity to apply the load that is applied by hydraulics in the expensive laboratory equipment.  When an early version of the instrument was shown at a club making convention, many asked that we make a machine for them when making our own.  Guiding weight without introducing friction lead us to invest in a milling machine.  Producing 15 machines for friends took all of our spare time for 6 months.  Today, 2 years later, databases with hundreds of shafts, are shared among the owners of the EI measuring instrument.

Shaft Alignment Author: | Posted in: Golf Club Making, Golf Shafts |

Shaft alignment has been debated by club makers for a long time.  A esoteric language evolved with terms like type 1, 2 & 3, N1, N2, NBP.  My experience and my understanding of the 8 page article, written by my friend, Dave Tutelman is the basis of this video.  There is a lot of misinformation about shaft spines.  Most of which is a based on so called spine finders.  These three point deflection devices show an apparent tendency of a shaft to snap to a particular plane.  This video show exactly what they measure and goes on to truly measure the radial profile of a shaft.