Putters

I'm almost sorry I opened this can of worms, because preferences in putters are so personal. Putter designs vary wildly, and you can find a pro having success with any of them. And now I have to do a major rewrite, because so much has happened in putters in the last 20 years (1997 to 2017) But I did bring it up, so here are some of the variants in putter design and what they mean to clubfitting.

What is the goal?

Most books on putting instruction have these three measures of  the goodness of a putting stroke -- often with others, but these three seem always to be present.
1. Hit the ball on the center of the clubface.
2. The clubhead should be traveling on the target line. (Let's use "target line" to mean the direction we want the putt to start, not mecessarily the direction of the hole.)
3. The clubface should be pointing in the target line.
We have learned a lot about golf science in the past few decades. Making sense of these lessons, the last of these is the most important -- perhaps the only really important criterion. Here are the arguments supporting my assertion:
• The direction the ball takes off is mostly in the direction of the clubface, slightly influenced by the clubhead path. The golf community has gotten used to thinking 80:20 as a rule of thumb. But a putter has almost no loft, so the "obliqueness" of impact is due only to the clubhead path itself. Given only a few degrees of path error, the ratio is probably north of 95:05. Put in other terms, a degree of path error is 20 times less important than a degree of face error. If you want to practice your stroke, spend a lot more time on where the face it pointing; the payoff is much greater.
• But what about spin? Won't a path error cause the ball to hook or slice? In a word... No! Hook/slice is an aerodynamic effect; the ground just makes the ball roll, and sidespin goes away almost immediately. Within the first foot or two off the putter face, the ball is rolling end over end with a zero-degree axis tilt (talking in TrackMan terms). There might be a bit of sideways skid before rolling starts, but the effect is small.
• The problem of an off-center impact is that the clubhead will twist, sending the putt off-line and perhaps slower. But today's putters are made with a very high moment of inertia. They resist twisting much better than the old blade putters. So it takes a much worse off-center hit to have the same bad effect on the result.
With all this in mind, let's talk about the characteristics of a modern putter, and the design features you should consider when fitting a putter.

Weight, moment of inertia, and balance

Probably the most interesting facet of  putter design and fitting is the distribution of mass in the club. There are three "moments" of mass that engineers deal with:
1. The mass itself, the "zeroth" moment of mass. This is the total mass of the club -- what you feel when you just pick it up and let it hang, or heft it at the balance point.
2. The first moment of the mass. This determines where the balance point is, and balance in a putter is important in all three dimensions. As a preview to what follows:
• The "balance point" of the whole club is along the axis of the shaft.
• Heel-toe balance can affect the direction of the clubface.
• Face-back balance affects the stability of face direction during the stroke.
3. The second moment of the mass, the "moment of inertia". This is most significant for putters in the resistance of the clubhead to resist twisting at impact.
All three have an effect on the performance of a putter.

Moment of inertia

In 2000, the debate between high-moment heel-toe weighted putters and centrally weighted putters was anything but settled. It is now. What had to happen was for the established pros who used blade putters all their lives to graduate to the senior tour or retire. I can't think of a single competitor on the PGA Tour who uses anything but a high moment of inertia putter. And you wouldn't recognize today's hi-MOI designs. At the turn of the century, the way putter head designers moved weight away from the center of gravity was to make the bottom flange at the heel and toe much thicker, therefore much heavier, than in the middle of the blade. Need more MOI? Either add more weight or make the blade longer so the weight is farther from the center.

The putters of 2017 aren't just heel-toe weighted; designers have all sorts of ways to move weight away from the center of gravity, which is how you increase MOI without increasing weight. The most popular high-MOI designs involve:
• Square-plan heads with a lot of weight at the corners. A very popular example is the TaylorMade Spider.
• Semicircular designs -- almost like a mallet, but with the semicircle just an outline of some heavy material (stainless, brass, or tungsten). An example is the Odyssey Three-Ball putter.
Why has this happened? Easy! A high-MOI putter is more forgiving of non-centered hits. With the old putter designs, a heel or toe hit twisted the clubhead during impact. The result was a putt both off line and short. If the head doesn't twist -- and moment of inertia is all about reisisting twist -- then the putt will roll straight and just as far as if impact were centered. With my high-MOI semicircular putter head, I'm not too concerned about whether the ball is centered on the face at impact; I just focus on face direction, and the putt goes where I want it to.

There are different ways to balance putters. The two most common are toe-down and face-balanced. Here is a picture of three putters being tested for balance.

The way to test a putter for balance is to lay the shaft on a flat surface like a table (or an egg crate, in this case) and see how the clubhead comes to rest.
• The Daiwa Pro Balance on the left is hanging toe-down, so it is balanced toe-down or toe-heavy. This is a characteristic of traditional blade putters.
• The Odyssey Two-Ball on the right is hanging with its face pointing skyward. The face is almost perfectly level. This identifies it as a face-balanced putter.
• The Carbite Polar Balance in the middle is between the other two in balance as well. It is an Anser-style putter with an increased moment of inertia due to tungsten inserts in the heel and toe. (If you read the previous section, you know exactly what this means and why.) It is as close to a toe-heavy balance you will find in a modern design.
Why would you choose one or the other as your putter. It depends at least in part on your putting stroke. If you putt straight-back-straight-through, face balanced is probably better for you. But if you putt on an arc, inside to inside, then toe-down may better match the feel you need to make it happen. But the differences are more in feel than in mechanical performance. Yes, there are measurable performance differences, but they are subtle rather than compelling. There is a correlation, but it varies from golfer to golfer; so you really need to test rather than just choose based on the arc of your putting stroke.

Jaime Gylan of the Royal Manchester Golf Academy has done a fascinating detailed test of how toe hang affects putting performance. He has shared the results in a video, which has sharpened my thoughts on this topic. One of the incidental takeaways of the video -- besides the results themselves -- is the technology available to fit putters in the 2020s. If you want to do serious putter fitting, you will need some way to actually measure what the putter is doing. Jaime uses the high end of the technology, the SAM Putt Lab. At the other end of the cost scale is the iPING app for smartphones. The phone clips to the putter, and the app uses the inertial sensors in the phone to determine what the putter is doing. There is a whole spectrum of instruments in between these two.

There are yet other ways to balance a putter.

One is neutral balance. (I use that term as an engineer or physicist would; the balance test shows neutral equilibrium. But putter companies' marketing departments have invented other terms for it, like "reality balanced" or "lie angle balanced".) When you use the same balance test -- rest the shaft on a table with the head hanging off the end -- the neutral balance putter will stay in any position you put it. There is no favored position for it to hang, like face up or toe down. The point is that the putter will just rest in your hands, with no tendency for the face to rotate.

This has pluses and minuses. While the face-balanced putter has no torques rotating the face dynamically during the stroke, neutral balance even eliminates static torques. The plus is that even gravity is not going to want to open or shut the face. The minus is that you lose the tendency of inertia to stabilize the face position during the swing.

Another is heel-down balance. This ignores the dynamic forces and focuses on gravity squaring the putter face statically. In the balance test, the face is perfectly vertical, so gravity will hold the putter face square. More on this below.

Let's look at a diagram to better understand the differences in balance regime for a putter.

The picture above shows four putters viewed from above, one for each kind of balance we have talked about. The green X is the center of gravity (CG) of the clubhead. The shaft comes straight down into the head, and exerts a force on the head -- the red arrow -- during the transition and forward stroke of the putter. (If the putter shaft were to have a bend in it, or end in a hosel well above the CG of the clubhead, then the force would act where the axis of the long straight part of the shaft intersects the plane of the clubhead's CG.)

But wait! There's a force we are ignoring: gravity. We can't see the force from this top view, because gravity always works straight down. But we do know it works through the CG. The picture above tacitly assumes that the interesting forces on the putter head act around a vertical axis. But the torques on the hands -- the interesting torques -- act around the shaft axis, the black centerline in the diagram to the right. And that axis is not vertical; it is on an angle, the lie angle of the putter.

Here's another diagram, looking at the putter face on. Here we can see gravity -- the weight of the putter head -- is the light blue vertical force. It can be resolved into two force components, the darker blue forces. One is "axial", parallel to the shaft axis, so it can't torque the clubface. The other is perpendicular to the shaft axis, so it might well exert a torque that twists the clubhead around the shaft axis. Note that the perpendicular component always points in the general direction of the heel; we will see that in the next diagram. Also note that the perpendicular component is nowhere near the force of the weight itself. It is a fraction of the weight, that fraction being the cosine of the lie angle. For a typical putter lie of 74°, the perpendicular component is only 28% of the clubhead's weight.

In the face-on diagram, the force causing forward acceleration of the putter head (the red force in the previous diagram) is straight at the viewer. It is on the centerline, the shaft axis, because the shaft is what is causing the forward acceleration of the head.

Here we have tilted the diagram of the four different putters, so that now we are looking straight down the shaft. (The shaft is the black circle.) We can look at all the torques around the shaft axis, the torques the hands on the grip have to contend with. Remember:

• The dynamic torque (due to clubhead acceleration along the line of the putt) is the red force acting through the CG, the green cross.
• The static torque (due to gravity) is the blue force acting through the shaft, the black circle.
So... Red force operates on green cross, blue force operates on black circle, to find the torques the hands have to deal with.

Let's see how each of the balance strategies helps the golfer, or puts demands on him.

• For the toe-down balanced putter, the force exerted by the shaft is not in line with the CG of the clubhead. To the degree the line of the force misses the CG, there will be a torque, the moment of the shaft's force. As the shaft pulls the clubhead forward, the torque tries to pull the face open. So the golfer's hands have to apply a counter-torque to square the face at impact. But it's worse than that for most toe-heavy putters. Because of things like shaft offset, the CG is also behind the shaft axis. so the blue force is also trying to pull the clubface open. The hands have to counter both static and dynamic torques opening the face.
Golfers who putt on an arc have usually developed a feel for applying this torque, because they have to for the arc stroke. The arc starts with the face open, it closes to square (ideally) at impact, and continues to close in the follow-through. The club's applying a torque to the hands satisfies the feel, provides the resistance the golfer has come to expect.
• For the face-balanced putter, the red force pulls through the CG. The CG's reaction force ("every force has an equal and opposite reaction" - Newton) pulls in exactly the opposite direction. Because the golfer's force (the red arrow) is in front of the CG and the inertial force is pulling backwards, it tries to keep that relationship. If the club were to turn during the transition or through-stroke, the force would no longer act through the CG; in fact, it would create a torque tending to bring the clubface back to square. That is what engineers and physicists call "stable equilibrium"; the face balance stabilizes the clubface square during the stroke.
That's nice, but all is not roses. The blue gravitational static force creates a torque around the shaft axis that wants to pull the face open. The good news is that this torque is the same throughout the stroke (that's what "static" means), so the hands can apply a constant torque and that will keep the face square. No need to adjust the torque during the swing. Indeed, users of modern face-balanced putters have gotten used to holding against a static torque, so it is not much of a problem for them.
• For the neutral-balanced putter, the force is applied at the CG. Not in line with it; right through it. So there is no tendency for the club to turn in your hands, neither due to acceleration nor due to gravity. But, there is also no restoring force if, during the stroke, you let the face become unsquare. If you do apply any spurious torque during the stroke, the dynamics remain completely neutral -- which is different from stable. Instead of being restored to square and in-line, the face will stay exactly where your hands put it.
• The heel-down balanced putter, is designed exactly the opposite of the face-balanced putter. If you recall, the face-balanced putter uses dynamic forces to keep the face square and doesn't worry about the static forces. The heel-down putter uses static forces to keep the face square and doesn't worry about dynamic forces. The blue force works through the shaft, and any deviation from square is countered by a torque from the blue force to square the face up again -- the classical definition of stable equilibrium with the face square.
The downside is the dynamic force due to clubhead acceleration; the design ignored it, but it is still there. And it tends to close the clubface, a dynamic torque that golfers are unfamiliar with; this putter may take a little getting used to. But it might work without much adaptation if the golfer has a pendulum stroke that depends more on gravity than grip torque. There is little experience yet with this type of balance, so I can't say much more about it.
I know of no reliable study comparing face-balanced and neutral-balanced putters. (By "reliable", I mean not sponsored by a putter manufacturer with skin in the game.) So we don't yet know which is better: not having to square the putter against gravity (neutral balance), or having the stroke stabilize face squareness (face balance). While we're at it, let's add heel-down to the not-properly-evaluated set; is it OK to make the most of gravity and ignore the acceleration forces? If I had to guess, the answer depends on the golfer; I strongly suspect some will do better face-balanced, others neutral-balanced, and still others with gravity-balanced. As with so many things, it's a fitting issue.

Weight and whole-club balance

In the mid-2000s, Steve Boccieri was putting the finishing touches on his Heavy Putter design. Charlie Badami, my good friend and a master clubfitter, was Steve's tour representative, going to professional tournaments, getting the pros to try it, and fitting them so it performed optimally for them. Many of the players that tried it did better with it than their own putter, even though most of those did not adopt it as their tournament putter for one reason or another. In the process of  fitting some of the best golfers in the world for putters, Charlie learned a lot about where to put weight in a putter, including both the head and the putter as a whole. For a decade, I kept the things he told me in confidence. But I've seen almost everything in public by now, so I don't think there will be any harm in disclosing it. Here's what I have learned from Charlie and Steve about weight placement in a putter.

Total weight. A heavier putter requires a big-muscle stroke to make it work. That's a plus. Modern putting instruction teaches that putting should be accomplished by having the body rock the shoulders, and the arms and hands should remain quiet. A heavier putter requires it.  How much heavier is the Heavy Putter? A typical putter, all up, weighs about 500 grams. The original Heavy Putter weighs in the vicinity of 900 grams. (The exact amount varies, as we'll see below.)

How heavy should it be? According to Boccieri (in the video on his web site), heavier putters for faster greens. The heavier putter requires you to use only the big muscles, and that is what you need for control on super-fast greens. The lighter putter allows more hand "pop" to give more ball speed on slower greens.

But wait! There is an opposing viewpoint on that. Paradigm makes a putter shaft with weights that can be inserted and secured to vary the MOI of the putter for different green speeds. And they believe that you want higher MOI for slower greens -- almost the exact opposite of what Boccieri recommends. I understand Boccieri's argument; I'm not sure I understand Paradigm's. But it seems that the world has not reached complete agreement on this.

Balance point. According to Charlie, the most important parameter for putters is the balance point of the club. His experience has been that every golfer does best with a balance point 12"-15" up from the ground, measured along the shaft. This is true with the heaviest Heavy Putter to a comventional-weight putter. The thing is that almost every putter other than Boccieri's has a balance point around 8", much closer to the head. Even though Boccieri's putters have a much heavier head than most putters (475g for the original Heavy Putter, vs 325g for most Anser-style putters), the Boccieri putters feel a lot less head-heavy -- and back that up with a high balance point.

They accomplish that with a massive counterweight at the butt of the club. No, we're not talking about the sort of counterweight you might use to backweight a driver; that is usually 15-25 grams. These are 150-250 grams, ten times as large. Why should that be? With a full-swing club, wrist hinge is an essential part of the stroke; indeed, it is the single most important factor in producing clubhead speed. With a putter, the opposite is true. The classic putting stroke involves a still left wrist. Even with a "pop" stroke, it is applied with the hands rather than the dynamic forces of a full swing.

I would like to speculate here on why this works. And it does seem to work. Steve says they did extensive human testing. I have observed and experienced quite a few cases of anecdotal testing that supports it. So what makes it work? Some of it is physics, and some must be feel. Consider the three putters in the diagram at the right. The red arrow is the linear force exerted by the hands; torque from the hands is not shown. The green cross is the balance point of the putter, and the dashed arrow is the moment arm of the force to rotate the putter about its center of gravity (CG is the same thing as the balance point).

Putter (a) is a conventional putter, with an 8" balance point. This leaves a large moment arm so, in order to move the clubhead along with the hands, the hands need to exert considerable torque in addition to the force.

This is completely solved by putter (b), which zeroes out the hand torque completely. It does so by extending the shaft well above the hands, and hanging a big honkin' piece of heavy metal there -- heavy enough to raise the balance point all the way to the hands. Now no torque is needed; the hands merely appy force, and the clubhead follows along. There have been several patents over the years suggesting this. None of them ever gained traction in the market. Perhaps it felt too "weird" just having the putter head follow the hands linearly. I'll get back to this shortly.

Putter (c) represents the happy medium between putters (a) and (b). It has a large, but hardly huge, counterweight. The counterweight is within the confines of a normal putter grip, not extended way above the hands. With the weight under the grip, it is impossible to raise the balance point all the way to the hands; i.e.- enough to zero out the torque. But it does raise the balance point much closer to the hands. This does two things: it reduces the torque required (because the moment arm is shorter) at the same time that it increases the static total weight of the club.

I just lied to you. Did you catch it? Going from (a) to (c), the torque actually doesn't change at all. Yes, the moment arm goes down because the balance point changed. But the that's on a higher mass, because it is the counterweight that moved the balance point. If you examine the forces involved, the torque should be exactly the same if the counterweight is centered under the hands. So what is the explanation?

My speculation is that the golfer putts best and with least effort with a particular ratio of hand force to hand torque (Force/Torque). More speculation: that ideal ratio is higher (more force or less torque) than what the typical putter design does without a counterweight. You need to increase the mass without increasing the torque, requiring a larger accelerating force from the hands, to get the ratio to where it should be. At some point, I'd like to work the math to see what the force-to-torque ratio has to do with the location of the balance point.

Back to clubhead balance. The original Heavy Putter had large removable weights at heel and toe. They could be selected to be different weights, changing both the weight of the clubhead and the heel-toe balance. Think of it like a face-balanced putter, but you can adjust the balance a couple of degrees either side of exactly face up.

In fitting golfers for the Heavy Putter, Charlie found that many -- even the Tour Pros -- had a bias in their misses. Moreover, that bias could be tuned out by unbalancing the clubhead toward the heel or toe. For him, this became a fitting fine-tune parameter.

There are other ways fitters can deal with such a bias. The way I see most often is changing the offset. But here is another way, if the putter head can do it. Sometimes, in fact, a particular putter head may be easier to adjust heel-toe weighting than offset.

Loft

Just for information at the start of the discussion, most putter heads you can buy are built with between 2° and 5° of loft.

There are two factors in choosing a putter loft: the speed of the green you play, and a particular claracteristic of your putting stroke.

First the greens. The putt begins with the ball sitting down in whatever height the grass is on the green. This might be distinctly down on a slow green with taller grass, or almost on a pool table on a really fast, high-stimp green. The function of loft is to start the ball at enough of an upwards angle to get the ball on top of the grass and rolling. Obviously, this requires more loft for taller grass, and very low loft for shaved, hard greens.

So what happens if you have too much or too little loft? Even with a putter, loft produces launch angle and backspin at the instant the ball leaves the clubface. If there is too much loft, there will be some period of bouncing instead of rolling (due to launch angle) and more skidding than necessary before rolling takes over. If there is too little loft, some of the same could happen, but for a different reason; a too-low launch could get kicked into the air by the grass it is stuffed into, resulting in bouncing.

Grips

There are more choices for putting grips than for any other club in the bag. Round, flat top, flat sides, paddle, square, pistol, jumbo, and now even super-jumbo; the Super-Stroke grip is a force in the market today. The rules even make several exceptions for grips, if the club is a putter. What works for you is what you should be using. There are no hard and fast rules, not even good rules of thumb. But here are a few things to think about as you consider your choice.
• The major test of a putter grip is if it lets you strike the ball with a square face. The shape of the grip should be one that allows the hands the best chance of doing just that. It is likely this is the most comfortable, relaxed grip to hold, but there is no assurance of that.
• The fat grip is a double-edged sword. The big radius from the shaft axis to the hands can cut both ways. On the one hand a 1mm movement of the hand turns the putter much less with the fat grip than a normal grip. On the other hand, any hand movement twists the clubhead with a higher torque, making the clubhead moment of inertia work harder to prevent twisting.
• Putter grips are usually heavier than other grips, and sometimes substantially so. I have used a putter grip weighing almost three times the 52 grams of a normal grip. That is not necessarily a bad thing, especially if you counterweight your putter; this will reduce the amount of counterweight you need to bring up the balance point. Just be sure you account for it in your design.

Shaft

I don't know how much there is to choose with a shaft. I doubt that flex gives a performance or feel difference (though there may be a sound difference, which contributes to perceived feel). The reason I say that is we have two facts both working against it:
• The forces and torques that bend a shaft are an order of magnitude lower than with full swings.
• At the same time, I measured the stiffness of representative putter shafts and found them considerably stiffer than iron shafts.
These add up to: the shaft hardly bends at all. And if it is not bending, then the flex can't do much for performance nor feel.

So what we have left is weight. There are lightweight graphite putter shafts, middle weight steel shafts, and I have used a few heavier shafts, all made of aluminum. Only one is deliberately trying to provide a heavier weight (the Paradigm, mentioned above), but it's a fact that the aluminum putter shafts I have used are heavier than steel or graphite shafts of the same length.

You don't see many putters with graphite shafts. The extra weight of steel or aluminum is consistent with the notion that a good putter has a high weight and even a high balance point.

The Tech-Line study

Before I leave this subject, I'd like to point those who are interested in learning more about putting and putters toward a series of articles that appeared in Golfsmith's "Clubmaker" magazine in 1992. The series is "Golf Putters and Technology" by Frank Werner and Richard Grieg, a couple of PhD Aeronautical Engineers who founded the Tech-Line company to make putters to their design theories. Now, 25 years later, the magazine is no longer around nor is the Tech-Line web site, so I have made a scan of the article available here.

I have listed below some of what they thought were important for putters back then. It is still pretty good advice, though there are other ways to get some of those important things today.

• Extreme heel-toe weighting, to increase MOI and enlarge the sweet spot. Their putter has a considerably larger measured sweet spot than others of the time. Today there are other places to put the extra weight that do as much good for MOI; modern designers move the mass back and around, rather than just out to heel and toe.

• Fairly heavy. All their models are between 320 and 330 grams of head weight, compared with 295 to 320 grams for most putter heads on the market in the early '90s. That doesn't sound so heavy today, but they were at the forefront of a trend that has continued.

• Face-balanced, to prevent any dynamic tendency of the putter to twist during the swing. Not many face-balanced putters on the market in 1992.

• A perfectly flat face; milling is the way they recommend. Their studies showed "face waviness" in popular putters, sufficient to cause errors of .5" to 2.5" in a 10-foot putt. Today it's hard to find a good-quality putter whose face isn't either milled or made of a carefully manufacture insert.

• A V-sole or single rail on the bottom, to immunize the putter to lie angle errors. They used a low-friction polyethylene rail rather than a V-sole, to simultaneously minimize the distance loss due to a scuff. (Their studies showed that minute, distance-affecting scuffs were much more common than imagined or felt by golfers, at all skill levels.) This never caught on.

• A well-designed "aim line". It should be perpendicular to the face (including the small face loft of the putter), long enough to be a real aid in aiming the putter (not just an indicator of where the sweet spot is), and prominent enough to leave a visual "trail" while swinging.

The Tech-Line putter never sold well, though that may be more due to inept marketing and sales than inherent merit of the product. I've used two of their models, and each had more years in my bag than any non-TechLine putter. So they got a lot right.

Ultimately, it's a matter of what the golfer feels comfortable with. There's no universal "right answer" for every golfer, and the variety is greater and less objective with putter than other clubs.