How to Match Shafts - 3

Dave Tutelman -- November 25, 2005

Matching an existing club

So far, we have talked about matching clubs in a set. But there is another matching scenario that clubmakers face all the time. Given an existing club, build another that matches the flex of the first. With the NF4, you can do a good job without disassembling the first club.

Actually, there are two levels of similarity to which you can match:

Match the overall flex of the existing club.
Match the flex profile of the existing club.

The first is flex matching of the sort you have been doing with the spreadsheet. It involves expressing the flex of the shaft as a single number, the target load. (Conventional frequency matching is also single-number matching; the number they use to represent shaft stiffness is the butt frequency.) The second matches the flex of the existing club at several points along the shaft; it is more likely to result in a club that plays and feels just like the first club.

Matching the flex of an existing club

If you just had to match a new shaft to an existing shaft, not a complete club, then you would know how to do it. The obvious steps are:

Place the existing shaft in the NF4 at an appropriate beam length, with the tip against the tip stop.
Measure the load. That becomes the target load for the new shaft.
Place the new shaft in the NF4 at the same beam length, and find the position of the shaft where it matches the target load.
Mark the shaft using the tip stop as a marking guide, and trim the shaft at that point.

The third step could be accelerated by the use of the spreadsheet, specifically, the "Woods" page.

But we have a few problems matching an existing assembled club:

The tip is covered by the clubhead, which extends beyond the tip. In fact, we don't even know for sure where the tip is, unless the club is a bore-through and we can see it.
The butt is covered by a grip, which adds diameter and perhaps takes away some stiffness.

How do we cope with these problems? Here's the procedure for matching an existing club. In this case, we are trying to match a new driver to an existing driver. But the approach can be extended to match dissimilar clubs: say, a new three-wood to an existing driver.

Choose an appropriate beam length: for instance, 32" for an iron or 38" for a wood. Place the club in the NF4, with the clubhead close to the tip stop. But be sure that the club only touches the NF4 where the bearings touch the shaft; if there is any interference between the NF4 and the clubhead or ferrule, move the club to give more clearance.

I usually position the club with the top of the ferrule even with the tip stop, as shown in the photo. That is close enough to give good results, and generally eliminates any problem with clearance.

Don't worry if the the back bearings rest on the grip instead of bare shaft. Theoretically, this could result in a less stiff reading than the actual shaft. But in practice, the error is less than 0.04Kg, so it can be ignored.

The grip does present a more troublesome problem: placing the club in the bearings. That's because the grip does not slide in the bearings the way a shaft does.

The best way to deal with this is to position the head end close to the correct position before you insert the club into the bearings. Then set it into the rear bearings first, and work the head end into the front bearings . That way, you minimize having to slide it. But you probably will have to slide it a little, perhaps up to an inch. Here's how. Hold the rear bearing block to keep it from rotating, while your other hand relieves the pressure between the grip and the rear bearings. You can master this with a little practice.

(Yes, you could remove the grip for the measurement. But, once you have mastered the technique of placing the club, it is much easier than removing and replacing the grip.)

If the digital scale on your NF4 is not on at this point (because you forgot to turn it on, or because the auto-off kicked in while you were positioning the club), you will have to turn it on. It is possible that the added diameter of the grip will provide enough load so the scale will refuse to turn on. If so, press down on the rotator board to take pressure off the scale while it turns on.

Now take a reading of the stiffness of the shaft. It should be repeatable to 0.03Kg or better. Record the reading, since it will be the target load for the new club.

Without moving the club from the position where you took the stiffness reading, measure the distance from the tip stop to the ground line of the club. This measurement, shown in the photo, is taken along the centerline of the shaft. Call this distance D.

Why do we measure D? The club's flexibility depends on the distance from some reference point on the shaft to where the centerline of the shaft would meet the ground. We are going to make sure this is what we match.

Remove the existing club from the NF4 and set it aside. All we need from it is the target load and D, and we have measured those.

Place the new shaft in the NF4 with the tip extended, and dry-fit the new clubhead on the tip. It is not necessary that this be a tight fit; in fact, a tight fit is probably undesirable. Carefully slide the assembly in the bearings until it has the same D measurement as the existing club. Be sure that the shaft is still properly bottomed out in the hosel.

Temporarily mark the shaft, using the tip stop as a marking guide. (A washable marker or a scrap of masking tape will do fine here.)

Carefully remove the head from the shaft, making sure that the shaft stays in the same position in the bearings. If it slides forward or back in the bearings, you have your temporary mark so you can replace the shaft as it had been.

Measure the distance from the tip stop to the tip of the shaft. Record that distance as T.

Alternatively -- and more simply -- you can remove the assembly from the NF4, remove the clubhead from the shaft, and measure the distance from the temporary mark to the tip as T.

Once you have recorded T, you can discard the temporary mark.

At this point, you want to find the position of the shaft that gives the same target load that you measured for the original existing club. You can find it purely by trial and error, or you can use the spreadsheet to give you an estimated trim.If you use the spreadsheet, use the page labeled "Woods".

Once you have found the position that gives the target load, leave the shaft in the NF4. As the photo shows, measure the distance T (the same T you measured before) to the right of the tip stop. Mark and trim the shaft there.

Now simply prep the tip and build the club.

Here are a few variations on the theme that you may encounter:

Not every shaft on the market will give you a match to an existing club. Here are a few problems that indicate you need a different shaft in order to match the existing club:

If the final step gives a mark beyond the tip of the shaft, you started with a shaft that was too stiff. A more flexible shaft is needed in order to match the existing club.
If the final step gives a tip trim that is too close to the end of the parallel tip -- so you can't seat the trimmed shaft in the bottom of the hosel -- you started with a shaft that was too flexible. A stiffer shaft -- or perhaps a shaft with a longer parallel tip -- is needed in order to match the existing club.

Suppose you are given an existing driver and asked not for an identical driver, but rather for a three wood with a compatible flex. The process is almost the same. The only difference is that you go for a different target load on the new 3-wood than you measured for the existing driver. Based on the stiffness slope you want and how much shorter the club will be, make the target load bigger than the measured load of the existing club. For instance, suppose:
- You measured the driver load at 3.25Kg.
- You want a slope (target load increment) of 0.30Kg/inch.
- The driver was 45" and the 3-wood will be 43", a difference of 2".
Then the target load for the 3-wood should be (3.25 + 2*.30) or 3.85Kg.
If you have a broken shaft in a set, you can read the completed club on one or both clubs in each side of the club in the set, using the techniques described above. Then interpolate between these two readings to determine the target load for your replacement shaft. For example, if it is a broken 8-iron shaft, you can measure the 7-iron and 9-iron, and average their readings to get a target load to fit the new 8-iron shaft to.

Matching the profile of an existing club

It is possible to match an existing club not just by a single flex number, but by the entire flex profile.Using the same type of methods discussed above to place the completed club in your NF4, you can profile the shaft of the completed club. Once you have a profile of the existing shaft, you can determine what other shafts that you have profile information for would work as the best replacement for the existing shaft. This is useful where:

The existing club is an OEM club, where the shaft is not available as a component.
The old shaft is no longer available.
The golfer wants a shaft that plays like the old one but is less expensive.

The process is a combination of matching an existing club and profiling a shaft. Here are some essential differences in practice:

You can't just slide the existing club from position to position. First of all, the shaft tip is not being pushed by the tip stop. Second, the longest one or two positions have the grip under the rear bearing, so the club will not slide. Therefore, you have to set the club at the proper position after you have changed the beam length. That is why it is useful to have a reference position that you can match by eyeball -- such as the top of the ferrule even with the tip stop.
Now that you are matching profiles, your choice of shafts is much more limited. It's obvious once you think about it, but you must choose a shaft that has a very similar profile to the existing club -- as well as a close enough flex so it can be trimmed to match.
Once you have found a shaft with a similar profile and a not-too-different flex, you will match the flex to the existing club exactly as you did before. In this step you are doing a single-number match, but you are doing it using a shaft with the same profile as the existing club.

A personal experience

Dan Neubecker relates the following example:

Here is a personal example where I combined several of these techniques to find the right replacement shaft on short notice. I had a college player come to me with a Titleist driver with a broken YS-6 shaft in it. He needed a replacement shaft installed immediately for a several day tournament that started the next morning. He had a Callaway Hawkeye driver with the same shaft in it and he brought that along, thinking I might pull that and use it. However, the Callaway was a .350” and the Titleist a .335”. He said that if I could match the Callaway shaft with one I had on hand, that would be close enough for him, but he needed it by the next morning.

I started by profiling the YS-6 in the Callaway, using the bottom of the through bore as the reference point to position the club. Then I went about profiling a bunch of shafts I had on hand. It turned out that an Aerotech Steelfiber 65 was a very close match in both profile and flex. I had to do a little tip trimming to match the flex. Then, when I installed the shaft in the Titleist head, I removed the old shaft to the depth of the Callaway through bore, leaving the dummy tip in place for the remainder. I did this so that the shaft would not play stiffer in the deeper bore Titleist than the YS-6 did in the Callaway.

The results were a resounding success. When the golfer played the finished club, he said he could not tell the difference between it and the original. And the shaft cost was about fraction of the cost of a replacement YS-6, had there been one available at that short a notice.

Last modified by DaveT - 12/19/2005