Clubmakers frequently ask us how to frequency match their Harrison grapite
iron shafts. Since clubmaker associations and trade magazines continue to
make frequency matching a hot topic, we decided it was time to share our
knowledge of frequency matching with you.
Frequency Matching Graphite Iron Shafts
The charts on the following pages describe how to frequency match a random
set of shafts. After following our instructions for frequency matching a
random set, you will be able to take your shafts and match them following
the same instructions.
The first chart (figure 1) lists some sample desired frequencies for
A, R, and F flex shafts. While your desired frequencies may be different
than the samples listed below, the increment between clubs should be 4 CPMs.
1: Desired Frequencies (sample only)
FLEX||R FLEX||F FLEX|
Sorting By Frequency
Now it is time to take a set of nine different iron shafts and begin
the matching process. The chart below lists nine assumed shafts and their
frequencies. Frequency should be obtained by using a 235 gram weight because
it is the most popular 2 iron head weight available in the component industry.
Notice that each frequency is matched with an iron (2 iron through PW)
2: Shaft Frequency Sorting Form
The matching process is very straight forward. First, take the lowest
frequency shaft (in this case, 284 CPMs) and mark it your 2 iron. Then,
take the next highest frequency (285 CPMs) and mark it your 3 iron. Continue
this process until all of your shafts are numbered. After you complete this
process, you should make sure the frequency and iron number are clearly
marked on each shaft for future identification.
Adjusting for Weight Discrepancy
Before you can actually frequency match the shafts, you must account
for how the iron head weights will affect your club frequency. The chart
below describes exactly how to do this.
The chart lists the "DESIRED" and "ACTUAL" weights for
a sample set of nine iron heads (column 1 & 2). In order to determine
how weight will affect your frequencies, you must first determine the gram
variances (A-B) between the actual and desired weights of the heads.
If an iron's actual weight is below the desired amount, you need to add
a weight pin to make up the difference. If an iron's actual weight is over
the desired amount, you must determine how much this weight overage (Column
C) will reduce shaft frequency.
4:Weight Conversion Chart
Weight (A)||Actual Weight (B)||Underage
(A-B)||Weight pin for underage||Overage||Overage
Difference (CPMs)||Standard Weight increment (CPMs)||Total
Overage and Weight Difference (CPMs) C+D|
The Weight/CPM chart shows how weight overage equates to reduction of
CPMs. The Weight/CPM chart is obtained by frequency testing a representative
iron shaft at 235 g, 237 g, 239 g, and 241 g to determine the respective
reduction in CPMs for increased weight.
|Weight (g)||CPM Equivalant
The information shown in the Weight/CPM chart is only an assumption.
Please keep in mind this chart will change for every model and every
flex of shaft. After you have obtained your weight overage, you can
use this Weight/CPM conversion chart to decide the overage differences in
terms of CPMs. The desired weights listed in column A of the Weight Conversion
chart were chosen after reviewing numerous component providers' specifications
and noting that these were the most widely accepted weights. The seven gram
increment between each iron head also seems to be an industry standard.
Based on the Weight/CPM chart, we know that for every seven gram weight
increase, the shaft frequency will be reduced by roughly 5 CPMs. Notice
that the Standard Weight increment listed in column D increase by 5 CPMs
for every 7 gram increase in iron weight shown in column A.
Now, take the overage figures in column C and add them to the CPMs in column
D. You now have the Total Overage and Weight Difference figures necessary
to match you set of irons.
Deriving Total CPM Adjustment
The next step is to take your nine shafts, each marked with a frequency
and an iron number, and place them in ascending order (see figure 5 column
A). Once you have done this you need to decide what the desired frequency
for each shaft is. (Figure 5 lists the desired frequency for a set of random
R flex shafts). Your desired frequency will always depend on how stiff you
want the shafts to be.
After determing the CPM difference between the desired frequency and the
frequency obtained using a 235 g weight, you must now factor in the Total
Overage and Weight Difference figures from the last column of Figure 4.
You will notice from the chart the various CPM differences between the raw
and desired frequencies. There are also CPM variations derived from the
Total Overage and Weight Difference. Add these two figures together (C+D)
to determine how much you need to tip trim each shaft.
Figure 5: Tip
Frequency CPMs) A||Desired Frequency (CPMs) B||CPM
Difference C (A-B)||Total Overage and Weight Difference
Taken from fig. 4 D||Total CPM Adjustment (C+D)||Tip
Trim Amount (inches)|
Deciding Tip Trim Amount
To determine how much tip trimming is necessary to obtain the desired
frequency for each shaft, you do not need to tip trim small increments to
acheive the desired frequency. Instead, you can push the shaft in the frequency
analyzer toward the direction of the tip while keeping the position of the
tip weight constant.
By doing this you will be able to see the frequency of a simulated, tip
trimmed shaft. If the frequency is what you desire, mark the position of
the tip that extends beyond the leading edge of the tip weight and trim
it off with a circular saw. Upon completing the tipping process, you can
now butt cut each frequency matched shaft to their respective length.
Remember, the tip trim charts describes a random set of shafts and does
not intend to give proper tipping amounts or desired frequencies for your
set of shafts. Because every shaft model and every shaft flex is different,
you need to determine the proper tipping amounts for every shaft model that
As a result, you need to take your own set of shafts and iron heads, measure
their frequencies and weight, determine tipping amounts, and decide on desired
frequencies and weight, determine tipping amounts, and decide on desired
frequencies in order to match your set. However, by carefully following
the above process with your shafts and iron heads, you should end up with
a frequency matched set.
While frequency matching is an effective way of building a set of clubs,
it is not the only way to determine flex. Harrison has always provided clubmakers
with tipping instructions based on shaft flex. These instructions, based
on flexes defined by a static deflection board, continue to be supported
by the great majority of shaft manufactureres worldwide.
Finally, whether flex is determined by frequency or static deflection,
it is very important to remember that flex is only one of many important
shaft specifications. As a club builder, you know that all golfers should
be matched with the correct torque, weight, flex point, and length. While
determining the correct flex for a player is important, it means very little
if the other specifications are ignored or minimized.
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