## Tuesday, April 16, 2013

### The Road to Golf Club Fitting Nirvana - Part IV

In part 3, I analyzed Monte Doherty’s worksheet a little more and discussed the ‘Ascending Weight Shaft’ theory. First, here’s a video going over the tools I’ve used for the MOI Balance Index.

I also use an Air Compressor for my grip installations. This means that I can remove the grip and measure it and then re-install it.

I decided to measure 3 of my clubs.

555C 4-iron

555M 5-iron

555M 6-iron

Each club has a matching MOI of 2,725 kg/cm^2 according to my MOI Auditor machine from GolfMechanix.

It’s really a toss-up between which club I hit the best in my bag…the 4-iron or 6-iron. I generally feel I hit the 6-iron superbly as judging by the wear mark on the face contact

However, I hit the 4-iron extremely well, too. The 4-iron feels a tad light in the head which is a common complaint with MOI matching and one of the reasons for MOI Balance Index.

First, I have to remove the shafts, the grips and the heads and then measure the components and input the data on the spreadsheets.

Simply get a digital scale and measure the weight of the *entire* club. Then when you input all of the data in the spreadsheet, it will total up the entire weight of the club. The weight in the spreadsheet should match (or come close) to what you measure on the scale. I use 2 different digital scales. One of them measures to nearest gram, the other measures to the nearest 0.1 grams. This allows me to triple check my work.

When I measured the 4-iron and 6-iron, I found that the MOI Balance Index were roughly the same. The 4-iron was at 39.6 and the 6-iron at 40.5. Thus, I split the difference and set a ‘target’ MOI Balance Index of 40.0. And the tolerance is +/- 2 from the target. However, I would rather keep it a little above the target MBI because the 4-iron feels a touch ‘head-light.’

If the 4-iron and 6-iron were graded as a ’10’ on a scale of 1-10; I would grade the 5-iron as an 8 out of 10. When I measured the 5-iron components, it came out with a MBI of 44.42.

This is not terribly off from the tolerance of the MBI (42.0). But it explains why the 5-iron’s performance is not quite up to snuff to the 4-iron and 6-iron’s performance.

The reason for this is that the trimmed shaft in the 5-iron came to about 1-gram lighter than the trimmed shaft in the 4-iron and 6-iron. I tend to think this is a bit of a QC tolerance issue in the shaft. However, it is a parallel tip (0.370) shaft that requires trimming from both the tip and butt end of the shaft and perhaps I made a slight error in trimming the shaft.

3JACK