Measuring Instruments for Golf Clubs


Do-It-Yourself Digital Swingweight Scale
The swingweight scale market is going digital. There are a bunch of digital swingweight scales on the market today. They are all priced at $330-$350. You can get a less expensive swingweight balance with a sliding weight for $50-$150; they are accurate enough, but slower and harder to read.

Or you can make your own digital swingweight scale. Here are plans for a digital instrument, where the parts cost is about $50.

Modify Your Swingweight Scale to be Digital
After I posted instructions for making your own digital swingweight scale, I started getting questions about modifying a conventional swingweight scale to be digital. Yes, it can be done, and here is how.

Dave Tutelman's Frequency Meter
In early 1996, I decided I really needed a frequency meter. Since most of my degrees are in Electrical Engineering, it was only natural that I should build my own. Here are the schematic diagrams for the circuit, along with a bunch of photos of the finished product. You might find the design of the clamp interesting, even if you don't build the circuit.

Frequency Matching With a Meter
The question comes up every month or so on various golf forums: "I just got a frequency meter. Now... how do I build a frequency-matched set of clubs with it?" Here's how I do it. It may be a little different from others, but it works for me.

Let's also keep in mind that this article does not deal with: How do I choose a frequency or frequency slope? That's a design issue. This article is limited to shop practice. It assumes you know the frequencies you want, and describes how to build the clubs to those frequencies.

Dave Tutelman's EI Machine
An EI machine shows a shaft's flex profile as the stiffness at the point where the measurement is taken. That may or may not be the best way for custom clubmakers to look at a profile, but it definitely is the way shaft design engineers see profiles. This article describes an EI machine I made and use, and the design considerations that went into it.

Errors in EI Measurement due to Shaft Weight
Instruments that measure EI tend to use substantial forces to load the shaft, forces way more than the weight of the shaft. For that reason, the shaft weight is usually ignored, on the assumption that it is negligible compared to the loading force. In fact, the errors are not necessarily negligible. This article gives an estimate of the errors introduced.

Precision, Accuracy, and Resolution
Too many people use the terms "precision" and "accuracy" interchangeably. They shouldn't. Precision and accuracy are completely different concepts. Let's explore what they really mean, and how to tell the difference. While we're at it, we will also throw in "resolution", which is also too-often confused with precision

Do-It-Yourself Shaft Puller
This article is about a Shaft Extractor, a tool that helps a clubmaker remove a shaft from a clubhead. The featured tool is one you can build for yourself. The original idea (including the key components) comes from Ron Blanchard, and I modified his initial prototype to be easier to build and more practical to use.

Do-It-Yourself Hosel Boring Fixture
If you ream out or re-cone hosels, it is easier, smoother, and an overall better job if you use your drill press and a hosel boring fixture. But the fixtures are expensive enough that most clubmakers do it with a vise and a hand drill. Here's a hosel boring fixture you can build yourself for less than $20 in parts, and it does the job just fine.

Club Ruler - New vs Old
As of 2004, the USGA and R&A introduced a Rule specifying how the length of a golf club is to be measured. Rather than measuring with to sole at the actual lie angle, it imposed an angle of 60. Since then, clubmaking tool catalogs have seen new club rulers designed to the new Rule. The question arises: "How different are the measurements of the old ruler and the new ruler?" This article answers that question.

Testing a Digital Scale
In working with golf club instruments, sooner or later you will encounter a digital scale or force meter. And you may well have reason to want to test it, to see if it is accurate. Most of us don't have lab standard weights around the shop, but it is possible to give the scale a pretty good test with things you are likely to have on hand.

Focal Plane Distortion of Shaft Bend
Pictures of shafts bending often have the bend exaggerated, due to the way digital cameras and even focal plane shutters work. Here is what causes the distortion, and a way to take photos that minimizes the exaggeration of bend.



 NeuFinder

The NeuFinder 4 (NF4) is an instrument to measure shaft flex and flex profile. It uses deflection rather than frequency. It is a major improvement to Dan Neubecker's original NF and NF2, which were not digital and, more importantly, not capable of being calibrated. I got involved with Dan when the NF2's weaknesses became apparent. We engineered the NF4 to allow calibration (so owners can exchange data) and to facilitate flex profiling. Most important, it was designed to allow a lab-quality instrument to be built by home craftsmen. Since that model, we have released a NF4.1 (an upgrade package) and an NF9 (a substantive improvement in ease of use, but no new capability). We keep talking about a complete rework and improvement, but we're both very busy and it stays on the back burner.

NF4 Load Reading vs Frequency
There is ample reason to want to be able to convert between the load reading from an NF4 and the corresponding frequency of the shaft. There isn't a simple conversion, but here is a pretty good estimator.

Shaft Deflection Profiling - Introduction
I have been using the NeuFinder 4 to profile shafts. Frequency profiling ("zone frequency") is a concept that is evolving and starting to catch on. This article shows that deflection can be as good or better than frequency for "zoning" a shaft. It also introduces some data reduction (which works for both deflection and frequency) that highlights the profile differences between shafts -- which might otherwise be masked by overall stiffness differences.

Shaft Deflection Profiling - Better Plotting
It is difficult to learn much about a shaft profile from a raw plot of deflection vs beam length. In the previous article, I introduced the notion of transforming the raw deflection load data to make the graph easier to read. Here is a much-improved data reduction transform. It is easier to understand, as well as no longer dependent on measuring some "standard" shaft. Instead, the data is subjected to a simple calculation not based on comparison with any other shaft.

Calibration Shaft Variation
As people have been building their NeuFinders, they have been posting the profile of their calibration shaft, as measured on their NF4. It turns out this can be a good sanity test, and has helped in finding and fixing bugs in a couple of machines. Here is a sample of six calibration shaft profiles for reference purposes.