What the numbers on a build sheet actually mean

Flex letters do not measure anything

The letter printed on a shaft is a marketing designation, not a standard. There is no governing body defining what stiff means, and there never has been. Take two shafts both labelled stiff from two respectable manufacturers, trim them to the same playing length, and clamp them in the same analyser: nine to twelve cycles per minute apart is completely routine. That gap is larger than the difference between many houses' regular and stiff.

So the letter tells you which shelf the manufacturer wanted the shaft on. It tells you nothing about how it will behave in your hands. What does tell you something is a measured frequency at a stated length, and that is the number we write on every shaft in the rack.

Butt frequency, in cycles per minute

Clamp the grip end, hang a standard mass on the tip, pluck it, and count how many times it oscillates in a minute. Higher number, stiffer assembly. It is a crude measurement in the sense that it describes the whole club rather than the shaft alone, and that is exactly why it is useful: the whole club is what you swing.

The number is meaningless without a length attached. Cut an inch off any shaft and the frequency rises roughly four cycles. This is why a sheet that says 265 cpm without saying at what length is not a specification, it is a rumour.

Frequency slope across a set

Individual numbers matter less than the gap between them. In a well built set the frequency rises by a consistent step from the long irons down to the wedges, typically four to five cycles per club. That consistency is what makes a set feel like a family rather than a collection.

Factory sets are rarely measured for this. A set can arrive with a slope that jumps eleven cycles between two clubs and then goes flat for the next two, which produces exactly the complaint we hear most: one iron in the middle of the set that behaves unlike its neighbours. Matching slope is most of what an iron bench session buys you.

Tip trim, and why raw length is on the sheet

Most graphite shafts have a specified tip trim schedule. Removing material from the tip stiffens the section that loads last, which changes launch and spin far more than the same amount removed from the butt. Removing from the butt changes overall frequency without touching the tip section behaviour.

Because both are options, the sheet records raw shaft length and tip trim separately. Without both numbers, nobody can reproduce your club later. This is one of the five fields on our sheet that is not for you at all: it is for whoever rebuilds the club in three years.

Torque

Resistance to twisting, quoted in degrees. Lower means less twist. It gets far more attention in marketing than it deserves, largely because it is one of the few shaft numbers manufacturers publish and it is easy to sell a smaller number as a better one.

In practice torque is a feel variable more than a performance one for most golfers. It contributes to whether a shaft feels harsh or smooth through impact. Where it genuinely matters is at the extremes of speed and at the extremes of off-centre strike, and if you are neither, chasing a low torque number is spending money on a specification you will not perceive.

Balance point and swing balance

Two different things that get confused constantly. Balance point is where the assembled shaft itself balances, measured from the tip. Swing balance is the traditional letter-and-number scale that describes how heavy the head feels relative to the rest of the club when you swing it.

You can hold total mass perfectly constant and move swing balance by two full points just by changing where the mass sits. That is why the sheet carries both total mass and swing balance rather than one or the other, and it is the subject of the longest entry in our bench log.

Total mass

The whole club on a scale, in grams. The number nobody asks about and the one that most often explains a tempo problem. A driver at 298 grams and the same head at 331 grams are different instruments, and the golfer who swings them will produce different transitions with each, regardless of what the swing balance says.

Total mass also drifts. Grip changes, ferrule replacement, a build-up of tape over three regrips: all of it adds grams somewhere. A club that felt right when it was built and feels heavy now has usually gained twelve to twenty grams at the butt end without anyone noticing.

Grip build-up, measured in wraps

The sheet records how many layers of tape sit under the grip, because that is the only way to reproduce the hand size you settled on. A single extra wrap is roughly a hundredth of an inch of diameter and around two grams. Neither sounds like much. Both are enough to change how much a hand can rotate through impact.

Most golfers who believe they need a midsize grip actually need a standard grip with two wraps under the lower hand, which is a five dollar solution to a problem usually treated with a fifty dollar one. There is a full entry on this in the bench log.