One of my winter projects is to build a couple of putters. Is there a good way to figure out the optimum putter length (I think I have seen this online and find this again) but more importantly the right head weight versus the length. I am not sure I have ever seen anything on this.

Thanks

Dear Old Caddie,

Here is a bit of info from Golfsmith:

"WEIGHT (Swingweight vs. Overall Weight)

The swingweight and overall weight of a putter are determined mostly by personal preference. Generally speaking, the shorter the putter the heavier the head should be. The standard head weight for a 35-inch putter is approximately 320 grams. Whereas the standard head weight for a 34-inch putter is approximately 340 grams. Based on the experience of fitting thousands of players, we are seeing more putters at 34 inches and under, as opposed to the industry standard of 35 inches.

Recent player testing performed by Golfsmith's Research and Development team indicates that many golfers may actually benefit from playing with a putter that is shorter than 35 inches in length. In the study, more than 100 golfers attempted five-foot putts with five different putters (all the same model) ranging from 32 inches to 36 inches in length. An artificial putting surface with no break was also used to make the playing field even.

Collectively, the golfers, who are average to better players, made 88 percent of their putts with the 33-inch putter, 84 percent with the 34-inch putter and 81 percent with the 32-inch flat stick. In comparison, only 78 percent of the putts went in the hole with the 35-inch putter and just 72 percent of the putts with the 36-inch putter found the bottom of the cup. Although informal, this test shows that the standard 35-inch putter found in most golf retail stores may not be the best fit for everyone.

The trend toward custom fitting is sometimes overlooked in this process. That is a mind-blowing statement considering that the putter is the club a player uses most in any given round of golf."

Here is a little more insight from Todd Sones:

"Swingweight

Swingweight is the most overlooked aspect of putter fitting, mainly because it is not visible. Swingweight has to do with feel. It is the feel of the putter head as it swings. Swingweight influences the distance the putter travels on the back and forth stroke. It influences tempo as well as the path the putter head swings. Swingweight is crucial to the fitting of a putter.

The swingweight of your putter should be close to the swingweight of the rest of your golf clubs. Industry standard for menŐs swingweight is D0-D2. WomenŐs is C6-C8. Whenever you alter the length of a golf club by cutting it down, gripping down it or even adding length to it, you change the swingweight. When you shorten a club, you decrease swingweight. When you lengthen a club you add swingweight. For every inch you alter the length of a golf club, you change the swingweight by 6 points. 1 swingweight equals 2 grams of weight. Ultimately, if you have shortened your putter or even grip down on your putter by one inch, you decrease itŐs swingweight by 6 points or 12 grams of weight. 6 swingweights is enough to drastically change the feel of your putter, your tempo and your stroke.

Another factor that most people arenŐt aware of is that when you buy a 33 or 34 inch putter off the shelf, the majority of computers use the same head gram weight no matter what length, which serves their purposes for reducing inventory of putter heads and increasing their profit margin. Using the same putter heads benefits the manufacturer, however it is a detriment to the player."

Golf Galaxy, based on Ralph Maltby, "weighs in" on this issue thus:

"Many heads on putters today are simply too light. The swing-weight scale is used simply as a way to determine if a putter head is too heavy, too light or in the acceptable range. The proper swingweight range for a putter is between C-4 and D-6. Ideally, C-6 to D-4 would be best.

The proper putter headweight promotes
the proper feel of the putter and, more
importantly, is another major factor in
distance control.

Too light a putter mainly hurts
consistent distance control but is
also a factor in directional control.

Too heavy a putter usually does not
affect directional control but it seriously
affects distance control.

The proper swingweight range for any conventional style putter in any length is very important it is another key putter fitting variable that most golfers are not aware of, but one that can benefit them immensely."

This is Ralph Maltby's discussion on his Blog:

"The trend has been to shorter length putters with heavier head weights. Heavier head weights in the range of C-8 to D-8 (D-2 is ideal) are necessary for consistent distance control with the putt. Research and testing with golfers has proved this out."

This is a Ralph Maltby page on Putter Fitting.

This is a rather interesting and technical discussion from HorsePowerGolf:

"Need to know what a "Swing Weight" is first?

If you can think of an object's weight as a measure of its resistance to being lifted. Then think of the swing weight as a measure of a club's resistance to being swung in a circle.

To a physicist, the proper term is "moment of inertia". The swing weight of a club is basically determined by the length of the shaft and the mass of the club head. Although other parts of the club make some contributions.

Anyway, clubs come in all different swing weights and it is important to match the swing weight of a club to your natural swing speed. Otherwise you'll get poor results.

If you have an easy-going, graceful swing, a heavier swing weight is called for. If you swing very quickly, then you need a club with less swing weight so that the club can rotate around your pivot point as fast as your body is rotating.

Swing weights are expressed according to an arbitrary scale that was created in the 1920s by Robert Adams. His scale (called a "Lorythm") includes: A, B, C, D, E, F. Each of these is further divided into tenths. So, a typical women's club will be close to C-4. A men's 7-iron might have a swing weight of D-2. Stick some lead tape onto that club head to make it more massive and its swing weight might jump to D-5.

Adams was a club maker for Francis Ouimet and Bobby Jones. He knew that (in principle) the golfer would be able to use the same cadence and swing from club to club if the clubs were matched according to their moment of inertia.

But through trial and error he came to modify the pure theory with a practical compromise that resulted in matching clubs according to a static measurement approximating moment of inertia about a point 14-inches from the butt end of the shaft. There is nothing magical about the Lorythmic Scale. It was just an arbitrary method of expressing the modified moment of inertia for a particular club.

TECHNICAL STUFF

For those of you who are technically inclined, the swing weight of a club is actually a measure of a club's moment of inertia about a point 14-inches distant from the butt-end of the shaft. Swing weight scales are designed to pivot around that point despite the fact that the hands actually rotate the club only about six inches from the butt end. Adams found, through trial-and-error, that "14-inches" was a good value to use when building clubs for professional golfers. It has been the accepted standard for 8 decades.

You might ask what the difference matters when the scale is arbitrary anyway.

For changes to the length of a shaft or to the mass of the club head, there really is no difference between results obtained with the 14-inch pivot-point and the 6-inch pivot point. Adding a given mass of lead tape to the club head will change the swing weight of a club by just about the same amount no matter which pivot point is used.

But changes to the grip mass will not be measured equally. Switching from a regular grip to a jumbo grip will lower the club's swing-weight. But not as much as indicated by a swing weight scale with a 14-inch pivot point.

Here's an example of what can go wrong due to the use of an industry-standard 14-inch pivot point swing-weight scale.

Say you've got this driver that you really like. The swing weight is just perfect for you.

But your hands are no longer as strong as they once were and you want to replace the regular grip with a jumbo.

So the fitter first measures the swing weight of the club to be D4.

The jumbo grip is installed and the club now measures at a D1 swing weight.

To restore the D4 swing weight, the fitter applies lead tape to the bottom of the driver head.

You go out to the range and find that the club just doesn't swing right. The club feels "too slow".

What happened?

Switching the grip from a regular to a jumbo appeared to lower the swing weight of the club by three units, according to the swing-weight scale. But that reading is false due to the fact that the change in mass occurred within the 14-inch pivot point. I.e., the scale saw the entire weight of the grip to lie on the butt end of the pivot point.

But that's not where your hands actually rotate. On the driving range, only about half of the mass of the jumbo grip resides above your pivot point and almost as much of the grip's mass actually rests below your pivot point, almost fully cancelling out!

In other words, switching from a regular grip to a jumbo grip doesn't really change the "feel" of a club during a swing. yet, the swing weight scale suggests that the change does have an effect.

Fortunately, there is no permanent damage. Most or all of the lead tape is removed and the club's "feel" is restored to normal even though the swing weight is now D1 and not D4!

MORE TECHNICAL STUFF

So the question begs: Why does measuring the swing weight at 14-inches from the butt end of the shaft work better than a purely engineered approach of matching the scientific moment of inertia?

In short, because the clubs are not treated 100% alike.

The driver, woods and long-shafted irons are struck with a sweeping motion, with the ball placed up in the stance (closer to the left foot for a right-handed golfer). The wedges and short-shafted irons are struck with a more pronounced downward motion with the ball positioned at the rear of the stance (closer to the right foot of a right-handed golfer).

These differences emphasize the need for distance with the long-shafted clubs and the need for accuracy, spin and control with the short-shafted clubs.

If all the clubs in a set were truly matched for moment of inertia, a golfer would have to strike all the clubs the same manner with the ball located the same place in the stance regardless of club. While that is not necessarily a bad thing, the golfer will quickly find that clubs are not designed to be struck that way. You sure don't want to take a divot with a long-shafted club.

So realize that Adam's swing weight invention was the result of empirical results gained through trial-and-error after beginning with a sound scientific principle.

More Info on Swing Weight

Swing Weight is the measurement of clubs balanced at the 14Ó fulcrum. It is an industry standard. It ranges from A-0 to G-2. The average standard of the major OEMs are at D-0. Swing Weight is actually more a feel of the club rather than performance. Clubs with different Swing Weight can feel the same due to the characteristics of the shafts that are assembled onto the club heads.

D-0 is the within the range that feels comfortable to the majority of golfers and that is precisely why OEMs make their clubs around this range. It does not necessary means that a person must use a particular Swing Weight. The higher the Swing Weight of the club, the more resistance you will find when you are changing from the Back Swing to the Down Swing. This means that those golfers who are stronger can handle higher Swing Weight. There is however a threshold for every golfer. The tolerance range differs between golfers.

Swing Weigh is constant from the 3 iron to the 9 iron. The pitching wedge and sand wedges normally have 2 to 3 swing weight points higher that the last. As it is measured at the 14 inch Fulcrum, extension of golf clubs in length will increase the Swing Weight.

Weight of shafts, club heads and grip affects the Swing Weight of a club. Changing to a lighter grip cause an increase in Swing Weigh but a reduction in Dead Weight which is a major factor in the performance of the clubs."

This is an interesting although not too detailed video clip of Ralph Maltby explaining the effect of swingweight on putting:



Here is a little discussion about tungsten weights dropped into the shaft as a technique to correct for lost swingweight from GolfWRK.com:

"Crosier

Nov 2 2007, 03:15 PM

So I found this little nugget online (pay special attention to #3-6):

1. All Swingweights are based on the raw weights of the club's components. The shaft is not to be cut to length in order to pre-calculate swingweight.

2. The balance point of the shaft, particularly certain graphite models, may change the final swingweight by several points. A lower balance point will increase the swingweight; higher balance points lower it.

3. A change in the head weight by 2 grams will yield a 1-swingweight change in the club. Heavier heads increase swingweight; lighter ones decrease it.

4. A change in shaft weight of 9 grams will yield a 1-swingweight change in the club. Lighter shafts decrease swingweight.

5. A change in grip weight of 5 grams will change swingweight by 1 point. Lighter grips increase swingweight; heavier ones decrease it.

6. A 1Ú2" change in the length of a club causes a 3-swingweight point change. Lengthening a club increases swingweight; making it shorter lowers it.

So given the above information, if I want to go from a C5 to D3 swing weight, I need to add approximately 16 grams of weight to the head of my putter (makes even more sense considering the original swing weight on this putter is D1-ish and 1" was cut off, decreasing it 6 total swingweight points). That's waaaaaaay too much lead tape, so I will definitely be dropping a few tungsten weights down the shaft and doing it that way."

This is some of what Frank Thomas has to offer:

"SWING WEIGHT

I read in one of your archived columns that wearing a golf glove adds swing weight. I only wear a glove during wet or extremely humid conditions in order to keep my hands dry. Will going from no glove to wearing a glove affect my swing in any way because of the added swing weight?
Peter, TX

Peter,
A glove has the same effect as adding weight to the grip of the club. Wearing a glove and gripping the club is in effect adding weight to the grip. This will decrease the swing weight by as much as five points.

The point I was trying to make in my exposure of this fact was that this will not affect your swing much at all from the point of view of the clubŐs balance. Without the glove you may be inclined to grip the club with a little more pressure which may not be good but from the point of view of otherwise affecting your swing, it has a negligible effect because the weight has been taken from the axis of rotation of the swing during the last phase just before impact.

The point is that swing weight, if used correctly, is a good first step in matching clubs. Counterbalancing by adding or subtracting weight to the grip is not a good idea as this may appear to have been balanced on a swing weight scale but may be dynamically significantly different when it comes to swinging the club. The overall weight and MOI of the club when measured about an axis a little above the grip is a better check of dynamic feel than abusing swing weight by counterbalancing.

Peter, donŐt worry about wearing a glove or not. If you need a better grip on the club and a glove does this for you, do it without concern.

I have been told that if you cut a putter down you change the swing weight. A former pro at our club would not cut a putter to make it shorter. He said I should send it back to the manufacturer and order one length you want. If you grip down on the putter, does it have the same effect of cutting it shorter? What do the manufacturers do to make a 32-inch and a 35-inch putter the same swing weight? Last, if it feels good, what does it matter what the swing weight? Thanks for any help you can give.

You are so right it hurts me. If you grip down on a putter it is the same as if you cut it down. Too many people pay too much attention to swing weight and in putters it is not nearly as important as in other clubs.

One of the newer golf enhancement products in recent years are (Balanced-Certified) drop-in weights to form a counter balance in your golf shaft. The product claims to improve center hits and to increase head speed in your woods and irons and a smoother stroke in your putter. Can you tell me more about this approach, how it works and whether or not this is truly being used on the PGA Tour? Isn't this similar to placing tape weights at the butt end of your shaft under the grip to make the club head fell lighter? What impact will it have on swing weight and should I care?

Thanks,

Adding weight to the grip is equivalent to wearing a heavy glove or a wristwatch. These will both in effect decrease the swing weight but have little to no effect on the swing dynamics or club frequency. If you like to tweak your clubs experiment with weight then get some lead tape and find something you may like. We have come to the standard weighting system after 400 years of trial and error. It can't be all that wrong.

I've been reading much about the "swing weight" of a club, but I don't have a clear idea of what that means. I play a natural fade (which sometimes turns into a full-blown pull slice) and have read that using lead tape to change swing weight, and the placement of the tape near the toe or heal of the club, may help to control this tendency. What can you tell me about this? -- Tom Abramson, Escanaba, Mich.

Tom,
Swing weight is a static balance, not the dynamic measure it implies. If a club is placed on sharp edge 14 inches from the butt end of the grip, and a weight is attached to the end of the grip to balance it in a horizontal position, then this weight determines the swing weight of the club. This is based on a conversion table, changing it to the numbering system we have all heard of (i.e. C9, D1, D2, etc.). Unless the overall weight of the club is also considered, the swing weight is meaningless. Putting weight in the shaft tip or the grip to make the scale read the right number is not the solution -- a swing change or trying to be consistent with what you've got might be though. Hope this helps.

I have seen the term "swing weight" used in Golf Digest quite often. Can you give me an explanation of this term and how it is defined? Thank you! -- Anon.

Anon -- I know another guy with the same name, do you think you guys are related? Swing weight is a static measurement, nothing to do with swinging the club. Roughly speaking, it's a measure of how the weight of a club is distributed. Imagine balancing a club on a knife edge (or "fulcrum") at a point 14 inches from its butt end. To make it balance, you'd have to add some weight to the butt end, right? The swing weight is basically a reflection of the amount of weight you would have to add to the end of the club to make it balance on such a fulcrum. Using an arbitrary conversion table, the numbers are converted to an alphanumeric code such as C3, D5, E2 and so forth. The lightest swing weight a club could have is A0; the heaviest is F9. The average is about D0, going up to D2 or D3 for stronger players. This is called the Lorythmic system (whatever that means) and is used by most manufacturers (a clubmaker called Robert Adams invented the swing weight scale in the 1920s, and successfully used it to "match" clubs for players like Bobby Jones and Francis Ouimet). Another system, not often used, employs a 12-inch fulcrum. This, ironically, is called the Official system (it isn't). Because it is a simple balance, swing weight is thus not the dynamic measurement its name implies. It does, however, if not abused, and used with the overall weight of the club, give some indication of the "dynamic feel or balance" of the club. You asked for it, Anon -- perhaps this was not the simple answer you were hoping for! I'll be writing more about swing weight in future columns."

Reviewing the Flatstick Forum posts, I found this analysis of "backweighting" putters and the effect on swingweight. There are a number of other links in this post.

The technical clubmaking articles by Dave Tutleman are always interesting, too.

Here are his four factors affecting swingweight (head weight, club length, grip weight, shaft weight).

These are Tutleman's formulae for swingweight and for MOI.

SO, LET'S SUMMARIZE THE ABOVE:

1. Most putters are too long at 35 inches, and 34 fits most people better for better performance.

2. Swingweight in the D-2 range seems about right for most people.

3. A 34" putter with this swingweight has a putter head of about 340 grams.

4. Roughly speaking, there are 4 factors affecting swingweight: head mass, shaft mass, grip mass, and club length, and these affect swingweight about like this:

+/- 2 grams head weight = +/- 1 swingweight point (e.g., + 2g changes D-1 to D-2);

+/- 9 grams shaft mass = +/- 1 swingweight point;

+/- 5 grams grip mass = +/- 1 swingweight point;

+/- 1/2 inch club length = +/- 3 swingweight points

5. Gripping lower on the handle is the rough equivalent of reducing the club length.

6. Backweighting and bigger / heavier grips reduce swingweight, but not as much as people think (the usual formulae don't apply because of the location of the change of mass in relation to the fulcrum point used for swingweight calculations).

7. Swingweight is not really that important for putting.

8. Swingweight only relates to the "feel" of the swinging of the putter when there is some braking or lagging-accelerating of the clubhead slower or faster than an effortless swinging -- kind off depends on how you like to swing the putter.

9. Swingweight from a manufacturing / design perspective is all about matching a "common denominator" swingweight to the "fattest demographic" of potential purchasers.

10. Swingweight from a custom fitting perspective is about optimal dynamics, optimal setup, the golfer's body, green speeds typically played, golfer tempo, and golfer need for "feel" in relation to tempo.

The usual deal is like this: A typical example is a standard putter of 35" with a head mass of 320 grams -- cut the putter 1" from 35" to 34" reduces the length 1" and also reduces the shaft weight a bit (perhaps 1 gram?), so the length reduction costs 6 SW points and the shaft mass reduction costs next to nothing. The 6 SW points are the same as 12 grams in the head mass. This can be adjusted for by a) a new putter head that increases the mass from about 320 grams to 340 grams; b) lead tape on the putter (takes too much tape); c) sand or a tungsten weight dropped into the shaft down to the hosel. It is possible to affect the change by also reducing the grip mass or the shaft mass, but these changes are not really effective (takes too big a change to catch up).

Incidentally, it is very unusual for a human to be able to notice any swingweight change involving less than 10% of the overall weight, so going from 320 grams to 332 grams is too hard to notice (only 12 grams, when 10% is 32 grams). Going from 320 to 340 grams really isn't all that noticeable either. You would probably have to go to 350 or more grams to really notice the change.

Personally, I think a head weight of about 360 grams is better than 340 grams for general purposes, with putter lengths of about 34 inches.

A more precise custom fitting is WAY more nuanced for the individual golfer than the usual deal.

Cheers!

Geoff Mangum
Putting Coach and Theorist

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Hi, when fitting much shorter people, specifically Asians, they need putters that are 28"-32" long. This means cutting them down far more than the 34" mentioned in your article as being 'acceptable'.

This whole swingweight issue seems a bit muddled. What i want to know is that if a person needs a shorter putter, it is generally because they are smaller, and thus a standard 340-360g putter head may already be too heavy for them. So if you cut a 34/35" putter down, it may feel lighter, but in reality the weight remains the same and the putter may then feel lighter and even more suitable to them and they should see increased accuracy as they are not swinging something that is not suitable for them in the first place.

If you go adding weight to the head for every 1" you cut off, then by cutting a putter to 28" must mean you have to attach a big gob of weight to the head to 'balance' it. This seems a bit off the mark...

98% of my putter fitting with Asians is 28-32". I am 6' 2" and I use a 32 1/2" putter (I have long arms and a nice bent over posture).

Would appreciate some clarity on this subject...

Dear David,

Swingweight is a bit of a made-up quantity. What it really relates to is the so-called "feel" of the putter head in the progress of the stroke. The masses of the putter and putter head bear on three separate effects registered in the "feel" of the hands: 1) lateral torquing of the handle inside the hands, 2) vertical slippage effects of the handle out of the grip, and 3) vibratory feedback into the hands. Swingweight per se relates solely to the first of these effects.

1. Lateral Torquing of Handle

When the putter head inertial momentum is opposed by the hands, there is a lateral torquing of the handle against the hands that registers as a feeling. The torquing increases pressure against the inside of the hands and fingers on the handle, which the brain interprets as "awareness of putter head mass in motion". This in turn means that without this torquing, there is NO significance to swingweight per se.

While admittedly there is very mild torquing at the start of the backstroke, since the putter head is being accelerated back from a dead stop, thereafter whether there is any further torquing is mostly a matter of the golfer OPPOSING the inertial momentum of the stroke-in-progress: to wit, stopping the backstroke, starting the downstroke, adding to acceleration thru impact or flinching, pulling the putter head out of its natural path, pushing the putter head out of its natural path, stopping the thru-stroke. At each of these points in that sort of stroke, the golfer's opposing the inertial momentum of the putter head causes the torque that registers as pressure increase against the mechano-receptors of the hand's flesh.

Does the golfer want to have this "feel"? Almost all golfers think they do, but I think they don't really know what is going on and what is at stake.

Loren Roberts, for example, says he allows his right wrist to break a little at the top of the backstroke, thereafter fixes the wrists in relation to the handle, and then makes the thru-stroke with a shoulder action. In this sort of stroke, there appears to be a resistance to the continuing swinging of the putter head by virtue of stopping the swing of the shoulder and arms resulting in the momentum of the putter head expressing itself in a breaking of the right wrist, which then overcomes and stops the momentum entirely as the golfer then "clamps down" the wrist muscles to maintain this orientation thereafter. Roberts says this helps his sense of "feel for distance". How that happens is pretty vague and elusive, but perhaps there is a little something worthwhile there. Perhaps the sense of setting the right wrist sharpens up his sense of form and timing for the balance of the stroke, and this indirectly gets associated in a fuzzy way with distance control. I'm fairly certain that one can have the same level of exquisite distance control without any of this right-wrist stuff.

And at any rate, the REAL trick here is TRANSITIONING from feeling the hands at the top of the backstroke to USING the shoulder to make the thru-stroke. Unfortunately, Roberts is quite good at this transition without discussing it (or perhaps even being aware of it), but hardly anyone else is, so that encouraging others to be aware of the hands at the top of the backstroke leads to USING the hands to make the forward stroke, which is very often the source and not the cure of problems.

So exactly what benefit this torque-feel at the top of the backstroke might contribute to the putting stroke is pretty undefined. So far as I can tell, if the motion is primarily a shoulder action, with body consciousness focused on the shoulders and upper torso, this hands awareness from the torque-generated sensations simply detracts from the stroke.

Does the "feel" help control the position of the hands during the stroke? Not really. The position of the hands is known in the brain mostly as "blobs" at the end of bones in the forearms. This sense of location of the hands in space is plenty sufficient for motion feedback and feed-forward signals used in controlling the stroke. Wanting to "feel" the hands change orientation to the handle by virtue of wrist angle changes doesn't significantly add anything to the motion control while it seriously risks the returning of the putter face square to the bottom of the stroke.

Is there a torque-generated "feel" in the forward stroke that aids distance control and square, online impact? Yes, to many. The sense that the handle is pressed back against the "seat" of the golfer's grip in the accelerating thru-stroke seems to correspond for many to the feel of a ball being tossed underhanded as the ball presses back against the inside of the hand. But what is really happening here? The pressure in the hands of this sort of accelerating stroke is due solely and entirely to the acceleration EXCEEDING natural gravity-sponsored acceleration in a swinging of the shoulders-arms-hands and putter in a coordinated manner. So the "feel" that results is not directly related to the velocity of the putter head at impact or at any other time, but to the consistency of the RATE of acceleration. (When an astronaut is accelerated to 2 Gs, he is pressed back in his seat by one extra G of force; if he is lying on his back in the seat with the rocket traveling straight up from the surface, he is pressed back into the seat with 2 Gs; the consistent RATE of acceleration corresponds to a very precise EXTRA pressure against the inside of the hand, so this cue is essentially all about the consistency of the rate of acceleration.) The physical "cue" of the pressure indicates to the golfer whether the acceleration rate is consistent from putt to putt. But this means nothing for distance control apart from the size of the backstroke: a consistent pattern of acceleration does not result in the required velocity of impact unless the total time of acceleration at that rate is correct -- and that means that the size of the backstroke must be correct for a given rate of acceleration to generate the correct velocity at impact for the distance and green speed conditions.

Is this sort of accelerating-stroke "feel" in the hands necessary or desirable? Not really.

In a broadly general way, a "smooth" rate of acceleration is the important component, and not a specific "feel" in the hands of the acceleration. The smoothness is also available as a cue in the movement of the shoulders and abdomen / back during the stroke, not only in the hands. The smoothness cue is also available by "doing nothing" to oppose the natural gravity-sponsored timing, which by definition is perfectly "smooth" since there is only one force of gravity that is always the same. And finally, if the quarry is some hands "feel" cue to help promote consistency, the best cue is "nothing changes" in the feelings inside the hands, as this is a more sensitive registering of accuracy than is "judging" whether pressure level X in a given stroke is the same as the pressure level the golfer expected to generate.

Is this sort of "feel" helpful or necessary to the form of the body in the thru-stroke? Helpful to many, yes, but not really necessary. Opposing the momentum of the putter head in the stroke at various points translates into a modest tightening of tension in the arms and chest. This slight adding to tension "firms up" the form of the stroke and gives the golfer a greater sense of being in "control" and the added definition to the form is a good thing. However, the definition of the form really needs to be set BEFORE the stroke gets underway, with the level of muscle tone being set as the level the brain anticipates to be needed for the impending forces of the golfer's stroke. (Gentle, mild-tempo strokes are less violent and these golfers can afford / need less muscle tension in the setup than do golfers with faster, more violent strokes.) The happy medium is using a mild stroke tempo so that the form muscle tone is not especially bothersome to instinctive fluidity and smoothness in the stroke motion. The greater the muscle tone at setup, the more wooden the golfer and the less instinctive.

So, to summarize thus far, swingweight goes along with golfers who are addicted to a psychological sense of control (whether real or illusory) by "feel" in the hands, but is mostly irrelevant to golfers using the upper body in a shoulder action with smooth timing.

2. Overall Weight and Vertical Forces in Hands

Aside from swingweight, you raise the question of fitting people of small stature with cut-down putters. Cutting down a putter affects swingweight, to be sure, but also affects overall weight of the club. The notion that standard putter head masses are too heavy for people of small stature does not ring true to me. Viewed as an issue of overall putter weight, the cutting off of a few inches of shaft reduces the overall weight of the club to a weight less than that normal for taller people, so that's pretty much a "wash".

The real issue for overall weight is how it relates to "feel" in the hands and arms in a vertical dimension and how it relates to the strength and sensitivity of the golfer. When a golfer holds a putter in two hands, not resting it on the ground, there is a slight vertical tug against the skin of the fingertips and palms groundward, and there is also an increasing tug in this same direction at the swing bottoms out between the top of the backstroke and the top of the thru-stroke (usually described as due to "centrifugal" force). The longer the rod between the hands and the putter head, the greater the "centrifugal force", from the formula: Centrifugal Force = Mass times (Rotational Speed)^2 times Radius, with rotational speed being the stroke velocity. So the centrifugal force peaks when the velocity peaks and is greater when the distance from hands to putter head is greater and is also greater when the stroke is more violent.

How does the golfer "feel" this? The golfer's skin experiences a "shear" force as the handle pulls outward with the swing of the putter head, slipping or sliding beneath the thumb tips and the flesh of the palms and other fingers, in a direction outward along the shaft line. If the velocity of the stroke peaks at the bottom of the swing arc, then the golfer gets a "cue" from this maximum shear about the position and timing of the stroke. The golfer uses this cue to monitor putter face squareness, as this is when the chickens in the stroke come home to roost!

How sensitive are people's hands to this sort of shear force? An instructive literature concerns design of teleoperation robotics for remote surgery, in which the high-frequency motions of the human hand are damped down to "steady hand" robotic motions. E.g., I. Emeagwali, P. Marayong, J. J. Abbott, and A. M. Okamura, "Performance Analysis of Steady-Hand Telemanipulation versus Cooperative Manipulation," 12th Symposium on Haptic Interfaces for Virtual Environments and Teleoperator Systems, 2004, pp. 316-322. See generally Doren, CL, "A model of spatiotemporal tactile sensitivity linking psychophysics to tissue mechanics," J Acoust Soc Am. 1989 May; 85(5):2065-80; Birznieks, I., Jenmalm, P., Goodwin, A. W., & Johansson, R. S., "Encoding of direction of fingertip forces by human tactile afferents," The Journal of Neuroscience, 21, 8222-8237, 2001.

Human fingertip detection of motion has a threshold near 1-2 microns of slippage motion occurring at an acceleration of about 2.5 m/s^2 (250 Hz), roughly one-fourth the acceleration of gravity. Howe, H.D., and Cutkosky, M.R. "Sensing skin acceleration for slip and texture perception," Proceedings of the 1989 IEEE Conference on Robotics and Automation, Scottsdale, AZ, May 14-16, 1989. At slower accelerations, the slip motion requires a greater displacement to be noticed, on the order of 100 microns for an acceleration of 10 Hz. It appears that the JND for contact force is 5-15 percent of the reference force value over a wide range of conditions involving substantial variation in force magnitude, muscle system, and experimental method, provided that the kinesthetic sense is involved in the discrimination task. In closely related experiments exploring the human's ability to distinguish among objects of different weights, a slightly higher JND of about 10 percent has been observed. Nathaniel I. Durlach and Anne S. Mavor, eds., Virtual Reality: Scientific and Technological Challenges (Washington DC: National Academies Press 1995), p. 166. "Humans can detect 0.06 µ high grating on the plate, owing to the response of Pacinian corpuscle fibers." Id., p. 170. "Humans can detect joint rotations of a fraction of a degree performed over about a second. The bandwidth of the kinesthetic system is estimated to be 20-30 Hz. The JND is about 2.5 deg for the finger joints, 2 deg for the wrist and elbow, and about 0.8 deg for the shoulder." Id., p. 171. Once slippage is detected, the human increases grip pressure non-consciously as quickly as within 70 microseconds of the detected slippage. Id. Johansson, R.S., and A.B. Vallbo 1979, Tactile sensibility in the human hand: Relative and absolute densities of four types of mechanoreceptive units in glabrous skin. Journal of Physiology 286:283-300; Johansson, R.S., and G. Westling 1984 Roles of glabrous skin receptors and sensorimotor memory in automatic control of precision grip when lifting rougher or more slippery objects, Experimental Brain Research 56:550-564; Johnson, K.O., and S.S. Hsiao 1992 Neural mechanisms of tactual form and texture perception, Annual Review of Neuroscience 15:227-250; Srinivasan, M.A., J.M. Whitehouse, and R.H. LaMotte 1990 Tactile detection of slip: Surface microgeometry and peripheral neural codes, Journal of Neuorophysiology 63(6):1323-1332.

The average putter total weight is around 490 grams, with the putter head mass being about 375 grams. The vertical force at the bottom with the putter simply suspended and motionless is given by the formula F = ma, or 0.49 kg times 9.8 m/s^2 = 4.802 Newtons. The force on the hands when the putter is swinging depends on the maximum velocity at the bottom of the stroke. A typical gravity-sponsored swing has a backstroke amplitude of about one-half a meter (50 cm), which corresponds to a one-meter length putter of an angle back of about 26.5 degrees with a height above the ground of 118 cm. The formula for the maximum velocity at the bottom of the swing is v = SQR(2gh). In the case of the backswing above, v(max.) = SQR(2 times 9.8 m/s^2 times .118 m) = 1.52 m/s. The Centrifugal Force at the bottom of this swing is then CF = mass times omega^2 times radius, where omega is the rotational velocity at the bottom in terms of radians/second. One rotation of a 1-meter radius circle is 2*pi*1m in circumference or 6.28 meters. A putter head traveling at 1.52 m/sec makes 0.24 revolutions per second (1.52 m/sec / 6.28 m/rev). A revolution has 2*pi radians, so this is 1.52 radians/second (0.24 rev/sec times 2*pi radians/rev). The CF, then, is 0.49 kg times (1.52 rad/sec)^2 times 1 m, or 1.13 Newtons. This is in addition to the stationary vertical force of 4.802 Newtons, about a 24% increase in force, well above the JND of between 10% for distinguishing "weights".

In the case of a golfer who accelerates the putter head thru impact faster than the gravity-sponsored stroke, at a velocity approximately 25% faster, or at about 1.9 m/sec, the CF would then be 1.77 Newtons, a 37% increase in force over the static 4.802 Newtons.

In the case of a shorter putter, the reduction in centrifugal force is directly proportional to the reduction in overall length. If you cut 10% of the length, you also reduce the centrifugal force by 10%. Hence, the above 24% and 37% increases would be mitigated by the shorter putter to 24% less 2.4% or 21.6% and to 37% less 3.7% or 33.3% -- still significant increases well outside the JND and potentially causing slippage and grip tightening.

Assuming the grip pressure was set in anticipation of this increase in force at the bottom of the stroke, then no slippage occurs and the grip pressure does not change. If the grip pressure is too light at the outset OR the swing is too violent and fast, however, the swing to the bottom can cause a tightening of grip pressure as the centrifugal force comes to bear on the contact between handle and fingertips, causing slippage. The take-home lesson is that setting too little grip pressure at address is a mistake, and the correct level of grip pressure has to take into account the anticipated maximum force at the bottom of the stroke. The human hand typically uses the least grip pressure for the task, and if that means the least grip pressure that holds the putter at address is used for the force of the motionless putter, then that grip pressure will fall short of what is required when centrifugal force is added by at least 24%. Hence, whatever is the "casual" minimum grip pressure for simply holding the putter suspended at address, it is probably safest to double this static pressure in anticipation of the stroke's centrifugal force increase.

3. Vibro-tactile Feedback

Reducing the length of the putter increases the frequency ("sharpness") of the vibrations generated by impact that travel the shaft into the hands. In so many words, cutting a putter down makes it "stiffer". On the other hand, adding weight to the putter head dampens the vibrations, so the vibrational frequency is lower or "duller".

Does this matter? My answer these days is "yes" because the brain anticipates the vibrational recoil of the stroke and associates this recoil with touch and solidness of impact. Once the golfer learns a certain association between solid impact and recoil vibrations, he manufactures a stroke to repeat that sensation or some form of it.

If a putter has been cut down and thus become stiffer with sharper vibrations on recoil, then the original "feel" can be approximated by increasing putter head mass, but I think it is a crap-shoot whether you could make the adjustment just right to restore the feel. perhaps the guys at Balance Certified Golf can tell us, as they are vibration experts from NASA. Vibrational physics is a bit beyond me at present, but I'm working on it!

Another approach is to change the shaft to a more flexible shaft. Raymond Floyd always preferred a shaft with a certain flex in it for his putters. At the low-velocity range typical for putting strokes, a flexing shaft will not seriously bother impact timing, but will be more responsive in impact recoil. The feel in the hands will certainly be less sharp.

In conclusion, I personally don't like modulating swingweight as an approach to managing lateral inertial and torquing forces, as this runs counter to the more vital "no changes" feel in a gravity-sponsored stroke. I also don't really like this for most amateurs who will never get this sort of gravity-sponsored stroke, simply because it encourages handsiness in the powering of the stroke to the degradation of form and touch. The vertical effect of the overall weight is a very legitimate issue, as golfers should have sufficient static vertical force that the overall heaviness of the putter tends to promote relaxed and fully-hanging arms without use of the hands, and should set grip pressure at the outset in anticipation of the likely increase in centrifugal force from the putter mass and the pacing of the stroke. The vibrational properties of the putter in recoil is also a legitimate issue, but is difficult to address with the cutting down of a putter without quantification of the vibrational frequency before cutting, or indeed without exploring other vibrational frequencies in search of something really good for the specific golfer.

So, when a 35" putter is cut down for a person of short stature to 28-32", the putter will lose swingweight and feel stiffer with a higher-frequency recoil vibration. It will also lose a little mass from 3-7" of shaft cut out (this is probably not more than about 15-20 grams of mass reduction in overall weight, say from 490 grams total to 475 grams total -- not that big a deal as the JND is about 45 grams anyway, so the reduction is not especially noticeable).

The real issue here is whether the golfer has a putter with sufficient overall weight for their strength and sensitivity and also has sufficient putter head mass so that mild-tempo swings get the job done on the typical greens played, without a constant sense of the need to add "flash speed" thru impact in order to make up for the lightness of the putter head. A cut-down putter doesn't so much "feel lighter" as it feels less "swing-y" and less "recoil-y". Since this can't be addressed practically by adding mass to the putter head, or can only partially be address, perhaps it is fruitful to consider changing the shaft to a more flexible shaft.

Cheers!

Geoff Mangum
Putting Coach and Theorist

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Geoff ... perhaps the term 'swingweight' is misleading vernacular. The static measure is the first moment of inertia while the dynamic measure is the second moment of inertia. How you feel, force or fight inertia defines your putting mechanics.

Do you differentiate between static and dynamic swingweight when it comes to putting with such a short and slow stroke?

Also, is it reasonable or feasible to just adapt to whatever weight putter head and shaft you use if you practice enough?? Using emotional feeelings to select a putter seems somewhat disingenuous in a physical sense. I say that because I find it simple to adjust my putting stroke to several styles of putters ... provided the shaft length is proper. I have difficulty adapting to putter lengths beyond +/- 1 inch.