CPM and flex Matching - What chart to use ? FCM ? What is flex slope?

Howard_Jones · March 6, 2020

This might be the biggest can of worms there is in club making, FLEX MATCHING of golf shafts.....Im a big part of the problem myself, posting a chart that later became pinned Topic, and years of debate after that where i tried to "tone down" what a chart like that actually is, and how limited value it actually got, but i feel like i left you with "half the story", so this tread about the topic should have been written many years ago, maybe things would have been different out there then?

THE FCM SYSTEM

The FCM system or Frequency Coefficient Measurement (system), is a Brunswick / Royal Precision invention by Braley (designer of RIFLE FCM) and Kim Braley (designer of Project X -now KBS shafts). Their system was the first of its kind with a numerical value as Cycles per minute, and part of this system is the FLEX SLOPE or flex progression from club to club or per inch if you like. The original FCM system used a 2.5" inch long clamp on the butt end only, and point zero or the charts starting point was a 43.00" long club. The FCM SLOPE was 8.6 CPM pr inch both ways from point zero like this:

Pay attention to that the FCM number is CPM value where we delete the first digit and divide the last 2 on 10, so a butt CPM value at 43.00" of 255 CPM = FCM 5.5 using a 2.5" clamp (old system pre-2012 , the new system post 2012 is described below) Then we see the difference with 8.6 CPM down pr inch when we go longer, or 8.6 CPM up pr inch when we go shorter.

1 CPM = 0.1 FCM so its 5 CPM from FCM 5.5 to 6.0, or 10 CPM from 5.0 to 6.0 who we consider to be "1 full flex" as difference
(if measured at the same play length with the same SW value)

ORIGINAL FCM CHART
- CPM changes with 8.6 CPM pr inch up or down from the 43.00" long club
Pay attention to that for the 43.00" long club, FLEX NUMBER is what we get if we remove the first digit (250 = 50 = FCM 5.0)

NEW FCM CHART USING A 5.0" clamp

From 2012, RIFLE is no longer making woods, and has changed from the 2.5" Clamp to using a 5.0 clamp - New CPM slope is 4.25 CPM between clubs or 8.50 CPM pr inch with the #6 iron as "point zero", since its now all about IRONS, but the actual point zero is a 45.50" long club where the CPM and FCM numbers match up again. 260 CPM at 45.50" is FCM 6.0 when we use a 5.0 clamp.

THE PRACTICAL USE
So, if we want to use the FCM system to find a starting point for flex on what ever club, we can use Butt CPM on the #6 iron, and then this "offset factors" we see on the line for FCM 5.5, so if i was planning to build a 43.00" long club, the start point for flex testing is a shaft who as 43.00" play ready measure 46.8 CPM less than my #6 iron. This WANT work if we change from HIGH or MID launch to LOW launch in the actual shaft, since LOW launch shafts is often weaker butt side than the matching "high launch" shaft, but we never got anything but a starting point for testing anyway, this is NOT a "buy suggestion" its a direction for where we should start TESTING.

FLEX SLOPE

The biggest issue with CPM and flex matching is that many tries this on NON - RIFLE FCM shafts, and try to force them to fit RIFLE FCM CHART - NEVER DO THAT.

Each shaft model has its own flex slope, and RIFLE FCM is 8.60 CPM pr inch, but thats NOT how other shafts looks like, some might be close, others is far off. Since i worked mostly with TRUE TEMPER product, my focus was TT shafts, and what i found was a difference on butt CPM slopes from 7.67 CPM pr inch all the way up to 12.67 CPM pr inch (vs RIFLE 8,6), so we CANT make our shaft model to fit another flex chart, but we can use parts of it, namely the #6 iron so we get a FCM rating and then we can use the offset factor to find a starting point for the rest of your clubs. To find the flex slope on the actual model we take the difference between butt CPM on the #3 vs the #9 iron / 3 = CPM slope pr inch.

LACK OF CHART COMPARABILITY DUE TO FLEX SLOPE
Since each shaft model has its own flex slope, "the chart" will not fit the terrain if we tried to use RIFLE FCM chart on a True Temper Constant weight shafts, because the natural flex slope of TT Constant wgt shafts is 5.87 CPM pr club, (BLUE) and RIFLE FLIGHTED (YELLOW) want fit the standard flight FCM chart either since FLGT uses a progressive flex slope to make them flighted so we need a separate chart for FLIGHTED. Here is how a club thats 328 CPM as a 37.50" club, equal to FCM 6.0 will look like as a SET #3 to #9, all numbers plotted on RIFLES FCM chart. The GREEN flat line is the values RIFLE FCM 6.0 would have as a SET of irons, the RED line is the average slope of True Tempers Descending wht shafts (very close to RIFLE FCM), and the BLUE line is the average for True Tempers Constant wgt shafts, who has a slope very close to RIFLE FCM FLIGHTED.

But make no mistake here, Constant weight gets its steeper slope because we dont loose weight when we go shorter, so if we look at the average slopes of 4.33 vs 5.87 the difference is 1.5 CPM who is LOST on the descending weight model, or added as extra wall thickness on the Constant wgt shaft. That means Constant wgt shafts has BOTH the tip trim slope, AND shaft wall thickness variables who both influence on flex, while the Descending wgt models only have the tip trim difference, and for that reason a flatter flex slope with lower CPM steps from club to club.

Compared we have this 4 we can use.

RIFLE FCM STANDARD - 4.25 CPM between clubs

TT DESCENDING WGT AVERAGE - 4.33 CPM between clubs

RIFLE FCM FLIGHTED - 5.66 CPM between clubs

TT CONSTANT WGT AVERAGE 5.83 CPM between clubs

IF WE MAKE CHARTS WITH IRONS WHERE THE #6 AS "POINT ZERO" IS USED FOR COMPARE
- WE GET 4 CHARTS LIKE THIS FOR "FCM 6.0" BUT EACH WITH ITS NATURAL FLEX SLOPE

If we now remove the decimals, we get to see that we have 2 charts really that actually covers the need. (see about TOLERANCES below)

TRUE TEMPER CONSTANT WEIGHT FCM / CPM CHART

Based on this knowledge, we can make a chart for DESCENDING WGT and another for CONSTANT WGT where we like RIFLE use the #6 iron as point zero, but here with the AVERAGE CPM slope for that weight type of shafts. Since the slope does vary from model to model, 1 club from #6 can be off by 0.5 CPM - 2 clubs 1.0 CPM and 3 clubs from #6 = 1.5 CPM (plus or minus from chart). We also have a tolerance from production we should set to plus minus 1, so the SUM TOLERANCE 3 clubs from #9 (#3 or #9 iron) is plus minus 2.5 CPM, so this chart can be used is we absolutely want a FCM vale for our IRON SET.

(+/- 3.0 when we round up the numbers to full numbers without decimals)

SUGG FLEX L is based on the earlier "conversions" between TT and Royal Precision - DO NOT think it will match the label on your shaft, its NO connection, so the chart is only compatible in one direction, we use CPM from the #6 iron to find the FCM value, the rest of the set is expected to be like this values, with the tolerance factors we see in the bottom of the chart.

True Temper Constant wgt models

TRUE TEMPER DESCENDING WGT FCM / CPM CHART

HOW MANY CPM IS "S FLEX" AND HOW MANY CPM IS "X FLEX"

This is the most misunderstood parameter of all. THERE IS NO COMMON STANDARDS for flex letter, they can NOT be used to judge how strong 1 model is compared to another. The flex letter is ONLY a address in that shaft model series with the actual weight. Example True Temper XP 95 S is SOFTER than True Temper XP 115 R, so all we get to know is that IN THIS MODEL AND WEIGHT, R is softer than S, and X is stronger than S, NOTING ELSE, so DONT even ask the question, it makes no sense what so ever since there is no standards for whats "S" or "X". We can only use this letters to navigate stronger or softer withing THIS model at THIS WEIGHT for that model, noting else.

High launch profiles most often has a stronger butt CPM than its brother model as low launch, both with the same flex letter. Thats why flex charts who specify what flex letter a certain butt CPM is, in reality is useless and based on misunderstanding of what its all about. Ive added the letters above, ONLY to show off what the old conversions between Royal Precision and True Temper was when TT bought Royal Precision, but they are anything but "correct for all", since thats NOT how shaft companies uses this letters.FULL SET CPM SLOPE -

TRUE TEMPER BOTH CONSTANT AND DESCENDING WGT. - SORTED by FCM rating strong to weak.#6 iron is basis for FCM ratio -
CPM SLOPE is ACTUAL and measured for the actual model. (used as basis for the average charts but here is the actual for each model)
Specs is "all standard" length, classic 4/8" between clubs, and SW value D2 or D3 depending on shaft /head combo.
Measured without grips using a 5.0" long clamp.

FLEX SLOPE EXTENDED - UNDERSTANDING CPM SLOPE FROM IRONS TO WOODS.

The FCM system was meant to be a system that covered ALL clubs in the set, so if we have #6 iron CPM so we can get a FCM value, we can look at that FCM value for a Hybrid or wood shaft using RIFLE FCM chart since those ratings is quite good if we stay in profile. (Consider RIFLE to be HIGH LAUNCH here, so if you look for a LOW launch shaft, SUB 10 CPM).

If we use each models NATURAL CPM slope (see row all the way to the right), and extend it into woods, the steeper the slope is, the weaker will the driver be.

A observation is that DYNAMIC GOLD X100 who has the steepest slope of them all, (makes the weakest wood) suggest a butt CPM of 269 for a 3W/43.00 club. If we look into HIREKOs databases for flex ratings, DG X100 WOOD shaft played to 43.00 has a butt CPM of 269. (but they was NOT designed by butt CPM but this tells that the steel wood shaft was designed as the counterpart to DG X100. Today we use Graphite to gain some club speed and play them longer, so flex need has gone up vs "back then". The same DG X player should look at woods in the FCM range 6.0 to 7.0 or 282 to 291 CPM if the club is 43.00 long. Thats a difference of 22 CPM UP, but if we use the FCM system instead it would have sent us to 289 CPM (High launch - butt stiff profile) or 279 (Low launch - butt soft profile).

One example for how we can use the FCM system to find a matching wood, again the DG X100 player - FCM 6.8 looking for a 45.00 Driver. The FCM system for FCM 6.5 is 269 + 3 up to FCM 6.8 = 272 CPM as HIGH Launch - Down to 262 as LOW launch. For compare a shaft like Grafalloy ProLaunch RED X flex who we know is a good match, has a average butt CPM at 45.00" of 266 (CPM Range suggested from the FCM system was 262 CPM as LOW launch to 272 CPM as High Launch), so it sends us to the right ball park, plus minus half a flex for a start point.

RIFLE FCM CHART STANDARD FLIGHT USING A 5.0" CLAMP (>2012)

Field 45.50" is color coded since thats where we can see the origin of the flex label where 250 CPM become FCM 5.0 etc. (it was the 43.00 club in the old system with 2.5" clamp)This chart should ONLY be used for RIFLE FCM IRON shafts- AND to identify starting flex for testing of woods where we use the #6 iron FCM rating as basis.

RIFLE FCM FLIGHTED MODEL 5.0 CLAMP (>2012)

Since the flex slope is way steeper, we ends up to soft with this slope to find woods of interest, so the FLIGHTED chart goes #1 to LW or 41" to 35" on Play length.

Use it ONLY for RIFLE FCM FLIGHTED. - BLUE indicated "softer and higher" - RED indicated "stronger and lower" all due to a different tip trim and butt CPM slope.

So now you have 4 different flex charts to use. RIFLE FCM only for RIFLE (and KBS shafts that has a FCM rating - see notes below)

For all other shafts, we either need to know the shaft models NATURAL slope. Look over the BUTT CPM chart above, you might find the model there so you get to know its FCM and butt CPM slope, but if its only for a "judgement", and its NOT RIFLE or KBS, then use the RED CHART for DESCENDING WGT sets (slope 4.33) or THE BLUE chart for CONSTANT wgt shafts (slope 5.83). That way you will have a chart that "fits good" since its based on the average for TT with a small deviation and tolerance. (be aware of that some taper tip shafts is descending wgt and some parallels are constant wgt, so never mix tip type and think its implicit what weight system that shaft belongs to. RIFLE FCM is descending wgt as both Taper and Parallels and PROJECT X is Constant wgt as both taper and parallels, while from True Temper we find mostly tapers as Constant weight, and mostly parallels as Descending wgt, but exceptions exist.

FLEX MATCHING

What do we try to match really? if its anything we try to "fix or match" its the shafts NATURAL slope, we should NEVER tune flex to please a chart on the wall, so "matching" is about to get the ORIGINAL FLEX SLOPE as "strait" as possible. That means if we want to judge each model correct, we need to start by making the slope and a chart for THAT model.

SLOPE = #9 iron butt CPM minus #3 iron butt CPM / 3.0" = CPM slope pr inch / 2 = between clubs in a standard set.

TIP TRIM or FLO?

Since flex matching involves a CPM reader, we can use that and take advantage of it to FLO shafts and mark them for WEAK and STRONG FLO lines. All shaft has a natural variable, they are not 100% no matter how its installed, and we can take advantage of that variable for flex match, by choosing some shafts with the WEAK FLO line target line, others STRONG, so the SLOPE for flex is matched, and tip trim avoided as long as possible. This way we eliminate or reduce the needed tip trim, since the shafts tip section is important for over all feel and flight pattern, and thats what we try to "even out" to be as "natural" and correct THIS SHAFT MODEL was designed to be.

Here is some specs from a set of True Temper Tour Prototype Monaco as TX flex. This shaft model had a slight progression in butt CPM as we go shorter (not constant from shaft to shaft, but stiffer and stiffer). I have put up 4 options for install to show how we can even out this progression so we keep the nature of this model. All shafts are first FLO tested and marked for WEAK and STRONG FLO lines. The first option is how the RAW uncut shafts looks like if they are all set to WEAK and the slope we get (not to be confused with play ready shafts, since this test is done with the same 285 grams wgt on all).

What we try to avoid is the RANDOM SLOPE where flex bumps op and down and quite a lot, so by mixing weak and strong FLO lines, we get the natural slope this model has who is "progressive". We can use the same method on all shaft model, and this way we can avoid using tip trim when flex matching, or reduce it to a absolute minimum. The "Suggested" option is the one i suggest using, non of the others, so look at the "improvement" on the Suggested vs Random, and think in terms of tip trim for how much we would have to alter tip trim to make the random option to become good....we should avoid that, and by using this method we can.

SPINE FINDERS is a useless tool, if we want to judge the shaft we need to know how strong it is in that position, so Spine finders and FLO without CPM might send us to the RANDOM slope since all shafts FLO good in that position, but flex ends up "all over the place", so dont use spine finder or FLO without CPM testing.

NEVER TIP TRIM WOODs for CPM REASONS

Woods is NOT designed to be "CPM matched", and todays woods often has a very limited length of the tip section, typical 3.0" only. Since insert is normally 1.25" and the ferrule takes a little, the maximum tip trim on wood shafts is considered to be 1.50" or equal to tip trim for a 7W. Wood shafts often respond with only 1 CPM for each 2/8", so if we tipped it to the max, 1.50'" we will most likely only see a gain of 6 CPM about 1/2 a flex class, but the shaft WILL NOT feel like that, it will feel "different" and not like a softer version of 1 flex letter stiffer. We can use 10 grams head weight = 0.5" tip trim as a norm, so tipping 1.50" is what we do to handle 30 grams UP in head weight. if it was irons we talk 4 heads shorter/28 grams up in head weight, but woods and irons is NOT designed the same way, and we dont use the same piece of the shaft

IRONS vs WOODS - We play a different part of the shaft

For irons we either tip trim our self or get pre-cut tips / Taper tips, and all clubs in the set gets THE SAME BUTT CUT down to play lengths...but thats NOT how it works for woods. IF we have a set with 3W - 5W - 7W and they are 1.0" in play length difference and tip trimmed as normal, we get to see that we go shorter 50% from the tip and 50% from the butt - AFTER 3W, so we can tip trim all shafts like it was for use in the 3W, then we take another 0.5" from the tip, and another 0.5" from the butt on the 5W and the 7W needs 1.0 cut from both ends.

So for woods, we use less of both ends (both shorter tip and butt section as we go shorter), while for irons we use the same length on butt section for all clubs, and thats why we see so many variables to the difference from drivers to woods, using the same shaft, because the EI profile and "what part of the shaft we use" is different, but NEVER tip trim a wood for CPM reasons, tip trim for FEEL reasons due to head weight. Here is how WOOD shafts looks like when we follow standard tip trim instructions (the best illustration i could make), and each segment illustrates 0.5 inch.

We shorten woods 50/50 between tip and butt side, so the shorter it is, the more "of the middle" we use, and less of both ends.

DO WE

GO SOFTER OR STRONGER WHEN WE BUTT CUT A WOOD OR IRON SHAFT?

This question has tricked and fooled way to many, so lets take it slow. The Butt section is ALWAYS the strongest part of a shaft, so when we go shorter on the butt, over all flex becomes softer, but it vary fro EI profile to EI profile how much. Lets use a driver thats 45.50" now as example (since that match with the latest FCM chart), and say this club measure 260 CPM with a 5.0" clamp = FCM 6.0.

If the plan is to reduce PL from 45.50" to 44.50" or 1.0" shorter we can move the shaft in the clamp so 1.0" inch comes out on the butt side like that part was already cut off. Now look at the return value. We cam from 260 CPM so if this club should "stay on the flex slope" for FCM 6.0, it has to measure 260 CPM + 6 CPM from 6 SWP lower + 8.5 CPM from going 1.0" shorter = 14.5 stronger or 274.5 CPM, and that will never happen. We mostly see return values from 266 to 270, where 6 CPM came from 6 SWP lower, so dont be fooled by a higher CPM number, dont forget that we have to judge this with the same SW value and the chart value at 44.50" to judge it right. If we DONT want or find the need to add head weight after going 1.0" shorter, the needed raise in CPM is 8.50 like the FCM slope is pr. inch, and we hardly ever go that much up either, so shorter butt section = softer.

KBS vs RIFLE

Kim Braley was one of the inventors of the FCM system together with his father, so its no surprise he uses that flex system on some of his KBS shaft models, but be aware of that KBS still used "the old system" with a 2.5" inch clamp (and by that different CPM values on the chart. Since the shaft butt might change the conversion factor between a 2.5" and a 5.0" clamp, WE CAN NOT use a fixed conversion factor between them, we should judge each model using the "correct clamp and corresponding chart" to make it right. As example, RIFLEs OLD CPM slope of 4.3 is not all that different from DG X100 when we measure DG X100 with a 2.5" clamp, but when we use the 5.0" clamp, the CPM slope progression difference becomes visible. So NO FIXED conversion factor from 2.5" to 5.0" clamps, it will vary from shaft model to shaft model.

ORIGINAL RIFLE FCM CHART - 2.5" CLAMP - KBS COMPATIBLE (RIFLE<2012 - KBS IS STILL USING THE 2.5" CLAMP)

END NOTES..

This post will be subject for editing of text by additional charts and or texts, and spelling errors will be made when found. i want to use this tread as reference when the question FCM and butt CPM flex comes up or flex questions in general where this tread might be relevant.

Edited March 11, 2022 by Howard_Jones

Howard_Jones · March 6, 2020

We can flex match both taper and parallel tips, both by turning /choosing weak vs strong FLO line, but also by tip trim. Most hosels accept 3/8" tip trim on taper tip shafts before we might get insert problems (hosel becomes to tight vs shaft OD). Since flex matching mostly is used on DESCENDING wgt shafts, and its hard to compare shaft WEIGHT with Constant WGT, ive made a few charts with focus on GRAMS PR INCH so we are able to get a apple to apple compare no matter direction.

DESCENDING WGT SHAFTS ONLY - GRAM PR INCH -

SHAFT WEIGHT IN THE CHART IS NOW DIRECTLY COMPARABLE WITH CONSTANT WGT TAPERS AS "UNCUT" WGT.

Example, we want to make a RIFLE SPINNER flex 6.0 - We need a 7.0 BLANK tipped as a #8 iron, but the weight compare is to DG as #9 or 37.00" and a 7.0 blank will be 126 grams as 37.00" so we talk the area of DG S200 who is 127 grams and typical for wedge use.

The same collection, now as estimated NET CUT WGT.

Basis is a BBGM of 1.25" and 1/8" butt cut for grip cap, a total of 1 3/8" difference to Play length.

For CONSTANT wgt (or AMT) we dont have the same "grams pr inch" for all shaft, but the same uncut weight as grams, and variable grams pr inch depending on what shaft in the set.

ESTIMATED NET CUT WGT CONSTANT WGT SHAFTS - 1.25" BBGM and 1/8" additional butt cut for grip cap - 1 3/8" total difference vs play length. (here standard #9 = 36.00")

WOODS - GRAMS PR INCH

You can read it as NET CUT SHAFT LENGTH AND WEIGHT.

If you dont know NET shaft length, its 1.5 to 2.0 inch shorter than the play length of that club (BBGM is typical 1.5 to 2.0" and maybe another 1/8" for grip cap)

Example, a 95 grams shaft uncut as 46.00 Long, played to 45.00" will be net about 43.00 or 89 grams installed. Since we on woods is down at about 2 grams pr inch, we have to "fail" by 0.5 inch in our judgement of BBGM to be off by 1 gram. so the shaft should be safe to use since weight tolerance from production is larger than plus minus 1 gram.

Reversed use, you find a 42.00 uncut hybrid shaft thats 80 grams....row 42.00" and 80 grams tells this shaft is 1.91 grams pr inch....and the option to that shaft might be a 41.00 long 80 grams...are they the same weight? NOPE 80 grams as 41.00" say its 1,96 grams pr inch, so if it was 42.00" long like the other, that shaft would say 82 grams.....dont let official specs fool you when you compare shafts, make sure you know GRAMS PR INCH, if you dont, then "grams and grams" can be many different measurements just like SW values, they loose meaning if we dont know the whole story and thats GRAMS PR INCH....

Its also grams pr inch we use to calculate weight gain or loss when hard or soft stepping since we gain or loose weight equal to 0.5" inch of shaft.DESCENDING WGT - WOODS HYBRIDS & IRONS - GRAMS PR.INCHFROM 2.76 grams pr inch and below = 46.00" wood as 127 grams, or a 41.00" long descending wgt iron / hybrid shaft of 113 gramsIts the same chart for all, since its grams pr inch that tells what animal this is.

FROM 1.72 grams pr inch and below = 46.00" wood as 79 grams, or a 41.00" long descending wgt iron / hybrid shaft of 70 grams

If you study the chart like it was a large PHOTO - you get to see the patterns of CONSTANT wgt shafts from the "pattern" or diagonal lines the same number as grams "draws" on the descending weight map. The progression rate from #3 to #9 in a set of CONSTANT weight is 11%, on the "Grams pr inch" chart, while AMT ends up with a progression rate of about 33% plus minus depending on shaft weight range. Steeper progression rate as grams pr inch the higher the shaft weight is.To be able to make a compare of 2 shaft and its "official weight" we need to know GRAMS pr INCH who is uncut wgt / uncut length, and thats what this chart help you with.

Stuart_G · March 6, 2020

This would be a nice article for the site.

Golfrnut · March 6, 2020

Just a thought Howard, having been there and done that with the "removal/install" tutorial. You may want to convert this to PDF also just in case something happens and your post gets wiped out. It's obviously a lot of work, and fortunately, you can also attach PDF files to the posts here so less chance all your work may be lost.

Howard_Jones · March 6, 2020

Adding a post with practical use of the weight chart....

Lets say you have a shaft on your desk, but have no idea "where you came from" or what that shaft was as uncut wgt, or how to pick a shaft with similar weight feel for a club next to it.

From the hips we say this shaft was net cut 42.50" and came from a driver, and feels "just right" and now the weight is 65 grams.

65 grams in the row for 42.50" say this shaft is was 70 grams uncut as 46.00" when it was new (Balance point might send us off a little but not much)

Another task: "Constant weight woods"

Now we want to make a 5W - and give thats 5W the same "feel of shaft weight" as our driver shaft gives.

The driver was 45.00 long, our 5W shall be 42.00" or 3 inch shorter.

We now start from the row for 45 long at 70 grams, and follow the 70 grams (1.57 grams inch) line on the chart to a 42.00 long club and we should end at 1.67 grams pr inch or 77 grams uncut shaft weight as 46.00 long for your new 5W. Then we have the "Constant weight" feeling, by making NET shaft weight the same. This difference of 7 grams shaft weight / 3 inch gives a progression ratio of 2.33 grams added shaft weight pr inch shorter.

If we want the same MOI value from each shaft, we have to go ASCENDING wgt with a slope steeper than to "constant weight woods", but the factor vary with shaft weight and play length, but for woods below 70 grams, use a progression ratio of 3.5 grams added shaft weight pr inch shorter, and for woods above 70 grams, use 4.0 grams as progression ratio. Compared to the "constant wgt woods" we can now choose 2.33 grams up pr inch, or 3.5-4.0 grams up pr inch.

In our example we got "constant wgt woods" by starting from a 77 grams blank for the 5W or plus (3 x 2.33) while for MOI we have (3.5 x 3 or 4.0 x 3) = 10.5 to 12 grams up from driver to 5W

HYBRIDS 80 - 110 grams use 5 grams added shaft weight to get shafts with the same MOI. (irons above 110 grams needs a progression of 6 grams pr inch like AMT)

Howard_Jones · March 6, 2020

TRUE TEMPER AMT SERIES

Since the tread is dedicated to shaft matching in general, both flex and weight, we cant finish up without some talk about True Tempers AMT series. Since AMT has progressive shaft weight, this shafts "moves" more in weight than normal when we hard or soft step them, but instead of seeing that as a "problem", see it as something that gives us options True Temper forgot to tell us about. Normally we can convert uncut shaft weight to "comparable shaft weight" by adding weight equal to 0.5" inch "lighter" for each Soft step, and 0.5" inch "up in weight" for each step when we hard step (see grams pr inch charts)

AMT is 3 series of shaft models, RED who is SEMI Ascending using COSNTANT wgt long irons, then Ascending wgt mid and short - RED is a "high launch" profile.

AMT Black is "MID weight and MID flight" and true Ascending all the way like White with 3 grams pr shaft or 6 grams pr inch.

AMT RED & BLACK SERIES

AMT WHITE SERIES.

Hard stepping "destroys" the AMT thinking very soon, while Soft stepping extend the weight progression into wedges so pay attention to how weight moves for each x we soft step. Normally we would not soft step a shaft 3 x but combined with "Tiger stepping" or 3/8" tip trim to adjust flex stronger we can stretch it to SS3 for weight reasons, while flex will be a little softer than SS2. Bare in mind that shafts thats lighter = thinner shaft walls = softer, so AMT is actually softer as they go longer compared to the original. Again a flex slope "personal" for the actual model.

I have not been able to measure out AMT options to rate them "correct" by the FCM system and conversion options we have (see post #1), so this chart is based on "older ratings" for the classic DG for R, S and X flex, and the normal soft stepping rules. AMT MIGHT play a tad softer than the chart for some models because the AMT #6 iron is softer than the classic DG #6 iron, but the chart is only made to give the ball park withing half a flex to make it easier to see what options we actually have for AMT. Flex tuning by tip trim /Tiger stepping is NOT included in the chart,

Howard_Jones · March 6, 2020

Good idea. but lets hope the servers on WRX is stable and good for a few more days until im happy with it.....You might have spotted the REAL reason for why im starting a tread like this, and does editing to older posts like my DIY Driver tune up?...Iwe been in "the making" of a book for years, but its always something forgotten, could have been formulated better etc....so its easier if i concentrate on "1 chapter at the time" and write for a wide but interested audience. Later this treads of good quality will be connected by a tread who works as a INDEX for each subject....

That means the "book" im writing want be on my own blog as the plan was, but a INDEX here on WRX with collections of "good treads" where im happy with whats delivered with education for the reader in mind. Those texts WILL be collected as PDF so the reader can down load all at one without the debate, but since it also links to the "original text", the option who bring that tread back to life and ask questions is possible. WRX Tech forum is the best plat form to reach out with Golf tech info, so why not take it to the max, and take advantage of the options it gives as a sum? this way i dont have to run my own blog and domain either, and its will always be available, also for the future and thats important for me.

One day i dont bother anymore, but what im writing about want go out of style for Club makers, and hobbyist club makers and thats the ones im writing for here. i try to do my best to clean up those many misunderstandings there is around different Golf club tech issues.

This "collection" that im doing is also educating for myself, i notice things i did not notice before what i did into my notes...its always been there, but i did not see it, so next post here i will add is about HOSEL SPECS and how we make 1 shaft to play as it did when we move it to a head with different hosel specs. Example the love for many, the old Original Grafalloy BLUE, played in a Bore Trough head design driver, and now we want to try the BLUE again, but in a modern Club head....We cant just relate on "todays tip trim instructions" when the shaft we deal with is from a different time where tip trim instructions was VERY different compared to now....

Il get back to that one, its a "baked in" part of how we deal with RIFLE FCM and KBS TOUR Parallels to make sure they play "dead on specs" (they hardly ever do, since Hosel specs vary, and PRE Cut shafts or Trim charts is based on a specific standard for Hosel specs...il tell you how to compensate both ways depending on what hosel specs you got, or "from hosel to Hosel"). Woods from driver via woods is part of that chapter.

So, when ALL is done, it will be "my complete book" for "How too" and how i mean we should do this , so SHAFT WEIGHT is one section - Flex match and Hosel Equalizing thats related to the flex question is another, FITTING (the existing DIY) is a third chapter, and i have tons of text collections to the building process itself from A-Z.....The works shop.....tools....yes is almost a book, when collected and "cleaned" and connected like planned, it will be, and free for all to use and share info from in non commercial cases. (no resale of text and info allowed, thats the only restriction)

T dogg · January 17, 2021

There's only one usefull chart there from 10 years ago

chipa · March 12, 2021

Thanks this is some great stuff I do my own clubfitting and have been using the CPM charts from Hireko to hard and soft tip the cheap shafts I buy in order to get it where I want it for my swing which is between stiff and x.

As it is now the I understand the lighter weight for the same cpm's will results in a club that plays stiffer.

I have played X100's but recently have tried the Apollo 95' and now the FST 115's because I have already maxed out the tipping for the Apollo's and while I like the kick I see it does cause me to lose it more to the left that I want. I think I need around 310 cpm's per Hirekos chart(5 iron std.) for my irons and as far as the woods I am now trying to use the Apollow wood shaft to see if I can get it to feel right. I had TT lite's but I never like how they feel. I have already hard tipped the Apollo wood shaft to the max and according to my linearly interpolated estimate I'm about 273 compared to the standard stiff cpm of 259, but it still feels a little soft so I'm going to cut off an additional 1/2".

Howard_Jones · March 21, 2021

If you want Descending wgt parallels to play stronger than max tip trim, we start with max tip trim, then we can hard step once or twice as we like to go beyond strongest tip trim option. (leaving butt cut as the last step we do.)

James Fowd · May 11, 2021

Hi Howard and others!

Howard's original post on this topic is simply marvelous. It has helped me understand so much. Thank you for that.

I do have a follow up question.

If I am building a set of clubs with descending weight parallel (.370) shafts and I know the slope of the shaft...would you recommend I tip the 6i to standard trim measurements and then adjust to the slope of the shafts from there. For example...Say I have a DG R300 .370 descending weight shaft. I would tip the 6i to recommended trim and then I would measure and trim so that the 7i is 4.5 CPM higher and so on and so forth. Is this correct?

Another follow up.

When you were measuring the CPM for the descending weight parallel shafts with a 6i head on and measured to D2 with a 50g split grip at standard length...Were most of the descending weight parallel shafts trimmed to the manufactures recommended tip trimming instructions? It seems like they were to make your chart as reliable as possible. Maybe I am incorrect which is awesome! I love to learn so any input would be wonderful!

Thanks!

rbpwrx · March 9, 2022

This is such an important topic, thanks to the OP for putting in the time and effort.

I have been building clubs for many years, but never really dove into FCM numbers and what they mean. But I've been wondering (and this could be stupid or crazy, so excuse the newbie question), but:

*Has anyone ever tried to build a set of clubs that truly match CPM, driver to wedge?*

(Closest example of this would be Bryson playing his irons at fixed length/ head weight. Presumably flex matches exactly, along with weight, torque, FCM, CPM, etc, b/c they're all basically the same club.)

So say that number is 350 CPM, for argument's sake. Would it be possible to build a set that matches CPMs through the bag? Driver at 350, wedge at 350, etc?

Not only that, would it be possible to match overall club weight through all 14 clubs? (I'm not saying it would be desirable, but would it be possible?) Not swingweight (not a fan), but club weight.

Obviously the shorter irons would be softer flex and the longer clubs would be stiffer. But isn't this kind of what we see anyway? Tour shafts go from TX drivers to X irons to S+ wedges. What if it were just a smoother continuum? Aren't they kinda frequency/ weight matching their clubs now, ish?

I don't mind different length clubs. Don't need to go full Bryson. But I do notice that I have to adjust my swing for each club based on different stiffness, weight, flex point, etc, even though they all theoretically 'match.'

Thanks for any thoughts.

Humbly,

Rolf in MA

Edited March 9, 2022 by rbpwrx
clarity

Howard_Jones · March 10, 2022

9 hours ago, rbpwrx said:

*Has anyone ever tried to build a set of clubs that truly match CPM, driver to wedge?*

So say that number is 350 CPM, for argument's sake. Would it be possible to build a set that matches CPMs through the bag? Driver at 350, wedge at 350, etc?

you missed the point. We do NOT want the driver and wedge to have the same butt CPM, they should be 85 CPM apart if the driver is 45.00" and the LOB wedge is 35" ( 10 inches each of 8.5 CPM in the FCM system)

Edited March 10, 2022 by Howard_Jones

Howard_Jones · March 10, 2022

9 hours ago, rbpwrx said:

(Closest example of this would be Bryson playing his irons at fixed length/ head weight. Presumably flex matches exactly, along with weight, torque, FCM, CPM, etc, b/c they're all basically the same club.)

Not only that, would it be possible to match overall club weight through all 14 clubs? (I'm not saying it would be desirable, but would it be possible?) Not swingweight (not a fan), but club weight.

All this questions was really answered in the posts above.
TOTAL wgt progression is a personal fitting parameter who vary from player to player, so the average of 15 grams pr inch is only a average and guideline, its NOT what every player should use, so YES we can match all parameters, but each parameter has to be set right for the player, NOT for "the system".

Stuart_G · March 10, 2022

14 hours ago, rbpwrx said:

*Has anyone ever tried to build a set of clubs that truly match CPM, driver to wedge?*

What do you think you'd gain by this? Not a set that felt or performed the same through all the clubs.

Matching butt frequency only "works" to give you a similar feel when using the exact same shaft model AND flex AND weight. Even just changing playing length makes it questionable - hence the need for the shaft OEM's to develop the various flex slopes. So once you change any of those (e.g. jump from an iron shaft to a hybrid or wood shaft), matching butt frequency would have no point and would be meaningless.

Edited March 10, 2022 by Stuart_G

Howard_Jones · March 10, 2022

On 5/11/2021 at 6:22 PM, James Fowd said:

Hi Howard and others!

Howard's original post on this topic is simply marvelous. It has helped me understand so much. Thank you for that.

I do have a follow up question.

If I am building a set of clubs with descending weight parallel (.370) shafts and I know the slope of the shaft...would you recommend I tip the 6i to standard trim measurements and then adjust to the slope of the shafts from there. For example...Say I have a DG R300 .370 descending weight shaft. I would tip the 6i to recommended trim and then I would measure and trim so that the 7i is 4.5 CPM higher and so on and so forth. Is this correct?

Another follow up.

When you were measuring the CPM for the descending weight parallel shafts with a 6i head on and measured to D2 with a 50g split grip at standard length...Were most of the descending weight parallel shafts trimmed to the manufactures recommended tip trimming instructions? It seems like they were to make your chart as reliable as possible. Maybe I am incorrect which is awesome! I love to learn so any input would be wonderful!

Thanks!

All shaft specs (compared) with different shaft models and flex slope, is ALL STANDARD...Standard tip trim, standard play length, standard SW value (D2 or D3), NO grips, all measured "play ready" (except for the missing grip), using a 5.0 clamp. Plain standard tip trim will give the flex slope we see, so unless we want a different slope and as example wants to tweak it against FLIGHTED (progressive less tip trim into the long, progressive more tip trim into the short, we just leave it as standard if thats what we want, of we can pick the #6 or #7 as Standard, and use custom tip trim for the rest (like 5/8" tip trim between clubs instead of 4/8")

golfnut1300 · January 12, 2023

I hope this reaches howard.

I just managed to get my hands on a set of New (old stock I think) Rifle Precision Lite FCM 5.0 (blue sticker) Taper tip shafts 0.355. On the top of each shaft is a little white sticker Which states a cpm ranging from 228 - 229 cpm.

My Clubs have a hosel of 0.370.

I looking at using your software (descending weight FCM) to build a set of MOI Matched irons as an experiment.

1st Question After measure the tip section using a shaft tip measuring gauge I believe there is some tip for me to trim if required. To reach a certain FCM.

2nd Question would you be able to tell me what the base FCM of the shafts from the following info.

club length weight tip length inch

3i 42 2/8 121g 8 3/8

4i 41 11/16 117.57 8

5i 41 1/8 117.33 7 3/8

6i 40 1/2 115.3 6 6/8

7i 40 113.75 6 3/8

8i 39 7/16 110.6 5 1/8

9i 38 7/8 112.43 5

pw 38 5/8 110.60 4 7/8

These shafts are un cut and the tips have not been prepared . Insert depth of my iron heads is 1 1/8 inch.

What effect on tip trimming and butt trimming effects the Cpm of these shafts.

I'm looking at building a set of Moi Matched Clubs With an Fcm of 4.7.

Any help would be gratefully received.

Howard_Jones · January 12, 2023

4 minutes ago, golfnut1300 said:

I hope this reaches howard.

I just managed to get my hands on a set of New (old stock I think) Rifle Precision Lite FCM 5.0 (blue sticker) Taper tip shafts 0.355. On the top of each shaft is a little white sticker Which states a cpm ranging from 228 - 229 cpm.

My Clubs have a hosel of 0.370.

I looking at using your software (descending weight FCM) to build a set of MOI Matched irons as an experiment.

1st Question After measure the tip section using a shaft tip measuring gauge I believe there is some tip for me to trim if required. To reach a certain FCM.

2nd Question would you be able to tell me what the base FCM of the shafts from the following info.

club length weight tip length inch

3i 42 2/8 121g 8 3/8

4i 41 11/16 117.57 8

5i 41 1/8 117.33 7 3/8

6i 40 1/2 115.3 6 6/8

7i 40 113.75 6 3/8

8i 39 7/16 110.6 5 1/8

9i 38 7/8 112.43 5

pw 38 5/8 110.60 4 7/8

These shafts are un cut and the tips have not been prepared . Insert depth of my iron heads is 1 1/8 inch.

What effect on tip trimming and butt trimming effects the Cpm of these shafts.

I'm looking at building a set of Moi Matched Clubs With an Fcm of 4.7.

Any help would be gratefully received.

Im not familiar with the LITE version, i never had any specs for them at all, so please send a mail to True Temper and simply ask if they have the same tip trim instructions as the standard FCM model. If the answer is yes, its strait forward, and i can do the numbers for you.

For the standard FCM model, we need the following specs
- Play lenght
- Hosel Total (BBGM + Insert)
- SW value (Moi is fine, but we need a base line from the club we duplicate MOI from)
- FCM blank (FCM 5.0 in your case)
- Blank flex (the white sticker you saw with 228-229 CPM, its measured with a 2.5 clamp and 255 gram tip wgt)
- FCM target
- Optional, is it a set with 4/8" or 3/8" between clubs?
- Optional, what flight pattern is wanted? Standard or Flighted? and where in the set do they change? (Flighted set has "1 standard" and longer irons with higher flight, shorter with lower, so we have to pick the iron where ball flight changes from standard)

golfnut1300 · January 12, 2023

Howard

Thanks for reply just emailed true temper and awaiting reply.

golfnut1300 · January 16, 2023

On 1/12/2023 at 1:10 AM, Howard_Jones said:

Im not familiar with the LITE version, i never had any specs for them at all, so please send a mail to True Temper and simply ask if they have the same tip trim instructions as the standard FCM model. If the answer is yes, its strait forward, and i can do the numbers for you.

Howard i got a reply from TT and they said yes same tip trim as the standard FCM model.

On 1/12/2023 at 12:54 AM, golfnut1300 said:

2nd Question would you be able to tell me what the base FCM of the shafts from the following info.

club length weight tip length inch

3i 42 2/8 121g 8 3/8

4i 41 11/16 117.57 8

5i 41 1/8 117.33 7 3/8

6i 40 1/2 115.3 6 6/8

7i 40 113.75 6 3/8

8i 39 7/16 110.6 5 1/8

9i 38 7/8 112.43 5

pw 38 5/8 110.60 4 7/8

Howard

If i was to soft step these shafts would that make the base FCM 4.7.

With the above shaft specs is it possible to convert them to a flighted set. The 7i would be the standard flight.

Howard_Jones · January 17, 2023

19 hours ago, golfnut1300 said:

Howard i got a reply from TT and they said yes same tip trim as the standard FCM model.

Howard

If i was to soft step these shafts would that make the base FCM 4.7.

With the above shaft specs is it possible to convert them to a flighted set. The 7i would be the standard flight.

The shaft set you have is PRE CUT to Rifles standard for hosel specs (butt cut only), so if you want me to do the numbers, you will have to deliver those specs im asking for above, i cant do anything without them. You will also have to tell what club numbers you will build.
Yes they can be soft stepped, both once or twice and they drop 0.4 for each step.

If this set can be modified to Flighted depends on the specs im asking for.
If MOI match by using the SW system is target (progressive SW value) i have to know what iron we shall duplicate resistance from.

Edited January 17, 2023 by Howard_Jones

tbrorson · February 16, 2023

On 3/10/2022 at 5:49 AM, Howard_Jones said:

you missed the point. We do NOT want the driver and wedge to have the same butt CPM, they should be 85 CPM apart if the driver is 45.00" and the LOB wedge is 35" ( 10 inches each of 8.5 CPM in the FCM system)

Howard, as you wrote " What do we try to match really? if its anything we try to "fix or match" its the shafts NATURAL slope, we should NEVER tune flex to please a chart on the wall, so "matching" is about to get the ORIGINAL FLEX SLOPE as "strait" as possible. That means if we want to judge each model correct, we need to start by making the slope and a chart for THAT model."

So, I have a follow up question. I want to frequency match my Hickory set. Why shouldn't I try to aim for the similar butt CPM for all clubs 36"-39.5" (not the wooden club heads)? Since the the hickory wood has less torsional stiffness compared to modern clubs, the longer clubs tend to twist. In this case it is "just" about sanding to find the right CPM. Why do we really want a CPM difference between each club, just to harmonize the modern shaft properties for the whole set? For my hickory set, wouldn't it be better to have the same stiffness (CPM) for all clubs? Any thoughts?

Stuart_G · February 16, 2023

18 minutes ago, tbrorson said:

Why do we really want a CPM difference between each club, just to harmonize the modern shaft properties for the whole set? For my hickory set, wouldn't it be better to have the same stiffness (CPM) for all clubs? Any thoughts?

I'll let Howard give the full answer - but the simple answer is that butt frequency is not an absolute representation of stiffness feel. Same frequency or cpm does not mean the feel will be the same. Usually that misconception shows up (in modern times) when trying to match the feel of shafts with different stiffness profiles or designs. But additionally, there are also several reasons why the stiffness feel can change as the playing length changes - even if the stiffness profile of the shaft is unchanged. The later is the reason that the various frequency slopes have been used over the years.

Edited February 16, 2023 by Stuart_G

Howard_Jones · February 16, 2023

8 hours ago, tbrorson said:

Howard, as you wrote " What do we try to match really? if its anything we try to "fix or match" its the shafts NATURAL slope, we should NEVER tune flex to please a chart on the wall, so "matching" is about to get the ORIGINAL FLEX SLOPE as "strait" as possible. That means if we want to judge each model correct, we need to start by making the slope and a chart for THAT model."

So, I have a follow up question. I want to frequency match my Hickory set. Why shouldn't I try to aim for the similar butt CPM for all clubs 36"-39.5" (not the wooden club heads)? Since the the hickory wood has less torsional stiffness compared to modern clubs, the longer clubs tend to twist. In this case it is "just" about sanding to find the right CPM. Why do we really want a CPM difference between each club, just to harmonize the modern shaft properties for the whole set? For my hickory set, wouldn't it be better to have the same stiffness (CPM) for all clubs? Any thoughts?

Let me turn it upside down.
- Why would you like to do that?
- What is the intention?

Hickory shafts and flex was judged by deflection, and still is.

tbrorson · February 17, 2023

Why I want to frequency match my Hickory set? I have the possibility, have raw shafts and need to sand then to "correct" flex.

My idea was to have similar CPM for all clubs, to have less impact of the lower torsional stiffness (for hickory wood compared modern clubs) in the longer clubs.

Don't know if the feel (as Stuart wrote above) will be the what I expect, similar for all clubs. Of course, the properties of the wood, grain etc. varies.

Why use a deflection board when the frequency analyzer is a much more modern, faster and more accurate way to work.

Why do we want a certain CPM difference between each club, is it to harmonize the modern shaft properties for the whole set? Or, will it give a feel of similar flex?

Howard_Jones · February 17, 2023

2 hours ago, tbrorson said:

Why do we want a certain CPM difference between each club, is it to harmonize the modern shaft properties for the whole set? Or, will it give a feel of similar flex?

If you did read the main post, you would not ask, but each shaft model has a certain and "personal" slope for butt CPM and deflection due to its design. Flex matching is done to make them all play as they was designed to play, unless we alter it by purpose for feel of flight pattern. its like any other blueprint job, we eliminate tolerances from production. When done the shaft SET would be like it was intended to be from the designer of the shaft.

And YES FEEL is part of it.
I never worked with Hickory shafts, but those STEEL shafts i know has a butt CPM slope in a standard set that goes from 7.67 to 12.67 CPM pr inch, or 3.83 to 6.33 between clubs.

Some graphite models have a flatter slope than this, like the model i play with 3.23 between clubs or 6.46 per inch. (mine is altered to 4.75 CPM between clubs or 9.50 pr inch to make them flighted.)

Edited February 17, 2023 by Howard_Jones

tbrorson · February 17, 2023

5 minutes ago, Howard_Jones said:

If you did read the main post, you would not ask, but each shaft model has a certain and "personal" slope for butt CPM and deflection due to its design. Flex matching is done to make them all play as they was designed to play, unless we alter it by purpose for feel of flight pattern. its like any other blueprint job, we eliminate tolerances from production. When done the shaft SET would be like it was intended to be from the designer of the shaft.

Howard, I did read your entire post, severel times, learned a lot! Thanks for clarifying things!

But, there are no recommentations or limits for Hickory shafts. No rifle, constant weight, tipping etc, (only the butt can be cut). As you say, we frequency match the design (and limitations) of the modern shafts. I guess the aim for the high end shafts is to minimize the CPM between each club? That is my original thought. The question is very theretical, I doubt I can sand them so accurate that they will be matched, but I just want to understan what I should aim for. 4-5 CPM between each club or same CPM? Looking for recommendations.

Howard_Jones · February 17, 2023

1 hour ago, tbrorson said:

Howard, I did read your entire post, severel times, learned a lot! Thanks for clarifying things!

But, there are no recommentations or limits for Hickory shafts. No rifle, constant weight, tipping etc, (only the butt can be cut). As you say, we frequency match the design (and limitations) of the modern shafts. I guess the aim for the high end shafts is to minimize the CPM between each club? That is my original thought. The question is very theretical, I doubt I can sand them so accurate that they will be matched, but I just want to understan what I should aim for. 4-5 CPM between each club or same CPM? Looking for recommendations.

You should ask someone who does flex matching of hickory shafts.
Each set is judged by deflection (Goose to Falcon flex)
Each set has a slope for deflection from long to short
NOW the question is, what is the NATURAL CPM flex slope in a set like that?

https://thehickorygolfer.com/hickory-golf-shafts

Thats what we do with all the others, fine tune them to their designed nature.

This explains a bit about the history behind it all
In the 1920s, iron sets often has groups of clubs with the same length, it started with 2 groups, then 3, then we get to where we are now with individual specs club by club...
To start with, they used 2 different shafts due to this, then 3, then individual

Its all about feel of flex and compensation for added head wht.

https://archive.lib.msu.edu/tic/golfd/article/1966jun35.pdf

Braley SR, is the man behind the FCM flex system who uses butt CPM for judgement, and part of it is its flex slope. They claimed "most player" would feel a more equal flex club to club when the CPM clope was 8.6 CPM per inch or 4.3 CPM club to club.

The problem with that is when we work with other shaft models that DONT have that CPM slope as nature, we DESTROY the shaft design by altering it in that direction, unless we know what we are doing.

Here is the school example
The GREEN Horizontal line is FCM 6.0 CPM numbers
The BLUE line is RIfle Flighted
The YELLOW line is DG S400

If we try to make ALL shafts in a set of DG S400 to play to FCM 6.0, we would need 1/8" tip trim for each 1 CPM stronger or 0.1 FCM stronger

#3 iron would need 4/8 tip trim (about hard stepped 1x)
#4 iron would need 3/8 tip trim (close to hard stepped 1x)
#5 iron would need 2/8 tip trim (about HS 0.5)
...when we get to the #7, we need MORE tip length in direction of SOFT stepping, since we are up at FCM 6.4 with out #9, so we will have to use a #8 shaft to get there for the #9
...what a mess, who destroys the shafts natural design and flight pattern, and it will actually become semi descending weight too, since the right approach (for this flex slope target) would be a hard stepped #3 iron, and a soft stepped #9,,,the others altered BAD inbetween them

So, you might improve TQ as you go longer in hickory by using a flat slope flex, but you will pay on the feel and weight account.

Edited February 17, 2023 by Howard_Jones

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CPM and flex Matching - What chart to use ? FCM ? What is flex slope?

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