That's typical of two influences: the putter itself, and the golfer trying to manage the path and face.
PUTTER SWING PHYSICS
All putters inherently will fan open in the backstroke when held by a golfer in the conventional manner. That is in addition to the golfer's chest fanning open when making a backstroke -- the putter fans MORE open than the stroke plane (defined by a plastic sheet laying top edge from each shoulder down to bottom edge at the putter head) unless the golfer's grip is firm enough to control the putter's inherent "fanning" physics. That's a golfer trying to move the backstroke with a "shoulder stroke" where the arms aren't moving independently of the chest and torso.
In the case of an "armsy" stroke where the arms move independently of the torso, moving further than the torso alone would send them, the arm pits open up -- at least the rear arm pit opens at some point in the backstroke. In that sort of stroke, the inherent physics of the putter held by the golfer's arms and hands will cause the putter to fan "open" out of the "stroke plane" defined by the two forearms, as if you laid a flat sheet of plastic on top of the forearms down to the putter head and then looked to see if the putter face was fanning open in comparison to that sheet of plastic. The putter face WILL fan open out of that "stroke plane" unless the golfer uses sufficient grip pressure to prevent it.
A "handsy" stroke is when the hands operate independently of the arms and move further than the arms alone move them. Golfers get real confused about this one, because so many people repeat the nonsense of using "sensitive fingers" for "exquisite" "touch and feel" and other undefined meaningless jargon words. Golfers "thinking" this sort of vacuous illusory "thinks" in the head don't really know what is moving what or how. A golfer with a "girly" light grip pressure who swings a putter back is going to experience the putter physics fanning the putter face "open" at the top of the backstroke, and that will move his hands out of the stroke plane defined by the sheet of plastic across his forearms. Many popular teachers think this is KEEPING the putter face "on plane", but frankly they are ignorant and use terms without defining them or knowing how they are using the terms. But that's typical golf teaching these days in the magazines and on TV.
All of this physics is readily understandable to anyone who has taken a high school physics class, but there is not evidence of that in golf culture. People like Scotty Cameron in jibberish posted on their websites (his claims about "toe flow" for example) don't even pass the laugh test of how putter physics works. All of the "heel-toe" versus "face" balancing nonsense has absolutely nothing to do with how putter physics actually works in a conventional stroke.
Here's how it works:
A putter coupled to the human body by the hands makes a total structure of putter, hands, and arms connected to the upper torso at the shoulder joints (arm pits). In the stroke motion, this shape gets moved by changing joint angles in the body somewhere, in some combinations of joint-angle changes. The simplest possible stroke would leave the arms and hands joints unchanged. That would be a HIP rotation that rotates the entire upper torso back and then thru. This hip rotation is performed by flexing the lead-side thigh to bend the lead-side knee and twist this leg to the back, and the backside knee simply gets out of the way until it's time for the forward leg twist of the backside leg to re-rotate the pelvis back forward. The trouble is this action is a bit unpredictable due to knees and the actual trajectory in space of the pelvis structure when moved back and then thru: the knees unevenly / unsymmetrically flex and the butt cheeks don't really match for movement. This causes big issues in coming back to the starting position in the forward stroke both online, square, and with putter face centered at the exact back of the ball on the start line of the beginning.
But the physics is that the whole shape of putter plus hands plus arms attached to upper torso is like swinging a bat, since the center of gravity of that shape is a) above the top of the putter grip midway between each forearm, and b) about halfway from there back towards the abdomen. That means that everything further from the body than this point in space is like a bat. Move it back and it will fan open by its own inertia; fail to grip it enough, and that inertia will move the body parts and change the angles open. To be a bit more precise about the inertial physics, a "bat" is anything with uneven heaviness out away from the center of rotation, which in this case we define as the center of gravity of the shape close to the stomach between the forearms. In typical "golf speak", a "face balanced" putter is one where the shaft is balanced horizontally and aimed thru the symmetrical center of the putter head mass, so neither the toe nor the heel see-saws lower than the other about the axis of the shaft; in comparison a "45-degree hanging" Ping / Cameron putter has the shaft aim thru the putter head more near the heel with extra weight on the toe side of this see-saw point, so the toe hangs lower down. The EXTRA mass on the toe side that causes this is not great -- perhaps 1/4th the mass of a golf ball? Maybe 10-15 grams, where a golf ball is 45 grams? A typical putter head will have a total mass of about 350 grams, so the EXTRA that gets the 350-gram see-saw to hang at 45 degrees is not that much. But that's basically all irrelevant to the real "bat" shape that applies when golfers hold a putter with 15 pounds of bone, meat, and fluid in the two arms and hands gripping less than 1.5 pounds (1/10th the mass) of a putter. So the "out there-ness" of the shape away from the center of gravity of the shape in a golfer holding a putter means the following in the stroke:
1. at the takeaway, the "heavy toe won't go", and this causes the toe to close initially, the more violent the takeaway the more the closing;
2. as the backstroke slows towards the top, the "heavy toe won't stop" and the face opens at the top of the backstroke, the more abrupt the stopping at the top the greater the toe opening;
3. changing direction at the start of the thru stroke, the "heavy toe won't go" and the open face gets MORE open in the forward stroke, and the more violent or quick the thru-stroke the more the face opens;
4. at impact, the "heavy toe won't stop" and the face closes thru impact to some degree depending upon the speed of impact.
Just hold a bat lightly at its end with the tip of the bat not quite on the ground (or better yet resting on a frictionless surface like the tip of the bat has Teflon and the surface is also Teflon) like a putter and make a backstroke and then a forward stroke.
Golfers get trained by their putters, when they should instead swing their tools like they meant something to take place instead of sort of letting the tool swing them. What really happens is golfers have good grip pressure at the takeaway to make sure they "tug the unwilling putter away" at the start, but then they get confused about what is moving what after that, especially at the top of the backstroke before coming forward.
So there is an inherent inertial physics in making a stroke that wants to change the body joint angles at the top of the backstroke to open the face out of plane, two times -- one stopping, and the next starting forward.
If you imagine making a hip rotation stroke with the arms and hands and putter in steady shape, but knowing you're swinging a bat shape, you can sense what the bat physics will due to promote the body joints to "open" at the top of the backstroke. If that doesn't do it for you, imagine making the same backstroke but progressively adding some weight to the putter head until you sense how that "out thereness" of the putter has inertial properties affecting the body shape -- out there being "out from the center of gravity of the total shape".
Stan Utley wrote an entire book purporting to describe what he personally did in his stroke movement for thirty five years and said he "rotated his shoulders horizontally" (that is, he rotated his upper torso with a horizontal rotation of the hips -- he wasn't quite able to get this part accurately articulated) AND he rotated his forearms [leadside pronating in the backstroke, backside supinating, then reversed going forward]. He said that this action "kept the putter face on the stroke plane". He also said that he used "sensitive fingers" and a very light grip pressure. Obviously, he is not making sense in his book, and within about a year of teaching after his book was published, other PGA teachers noticed and told him that what he described in his book and his clinic explanation wasn't at all what he actually did when he demonstrated his stroke. So his whole book is completely wrong and he acknowledges this. Eventually, his friend and teacher Rob Akins in Memphis explained to Stan what he REALLY does for movement when he makes a stroke, and now Stan tells people that he makes a stroke straight back and straight thru on a tilted plane with no forearm rotation. But the book still sold.
Moving on to the next movement pattern, that is not a hip rotation, but a stable lower body and a torso motion above the stable base. I never find any golfers or golf teachers knowing what muscles and joints might be involved in making this move -- zero human anatomy knowledge. The "joint" in this case is the way the spine at its base connects to the pelvis, and the muscles are those that connect the rib cage of the upper skeletal structure to the pelvis and the lower skeletal structure. Those are primarily the inner oblique abdominal muscles, that when contracted tug one side of the rib cage towards the top of the pelvis. That moves the entire upper torso. If you stood upright with both hands in the air and did this on the left side, your hands would point from 12 o'clock to, say, 11 o'clock. AND your left hip would slide to the right. Depending upon the stability of the lower body in the legs, your knees might or might not flex a bit also. Then if you bend the upper torso a bit forward to balance the weight onto the balls of the feet so your naturally-hanging arms with the hands beside your pockets now hang down towards the toes of your feet, that would be a conventional putting address posture. The hips in making that lean over will back up from normally above the arches of the feet to now above the heel, about 6" back, to place the butt as a counterweight to handle the weight of the upper chest and head going towards the toes. The end result is shoulders above balls of feet, hips above heels, hands above toes of feet, weight mostly on balls of feet and not too much onto toes or too much unweighting off the heels. From that posture, the "move" of the upper torso ONLY with the inner obliques with the hands up will still move the hands from aiming at 12 o'clock to aiming at 11 o'clock.
But now bent at address like this golfers unmindfully use the back muscles instead to rotate the spine and hips instead of tugging the rib cage down. The right back muscle tugs the right hip back off the heel, and on the left side the left knee flexes to allow that; the right butt cheek backs up and the left butt cheek goes forward. The hands then aiming at 12 move to aiming at 1 o'clock. Those two moves are completely different: the first one does NOT change the plane of the shoulders in the movement; in the second one, the back muscle twists the plane of the chest and torso and shoulders out of its initial orientation into an "open" orientation in the movement.
So, depending on whether you know what you're doing in making the shoulder move above a stable base, your hips may get rotated in the backstroke. If that happens, your shoulders and chest will move out of plane in some rotating manner open. To avoid that, think "move the side of the left rib cage right down at the middle of the left foot and that will make the shoulders rock in a vertical plane without the chest twisting around open over the hips."
So that gets rid of the movement source of the opening of the face out of the address orientation, but you have to use enough grip pressure to keep the "bat" under control also, or else the bat will open in the backstroke and change the orientation of the hands and forearms at the top of the backstroke. The bat will then open the putter face OUT OF the swing / stroke plane of the shoulders / arms.
Seve Ballesteros is the only person I've really seen teach to hold the lead side of the pelvis steady when making the backstroke. Great, but no one recalls him saying it in the 1980s. That in itself doesn't choose the move that aims the hands-up to 11 o'clock when starting the backstroke, but it at least provides a way to get back to face square as at address when the upper torso rotates the hands-up to 1 o'clock in the backstroke. The actual method requires a conscious tensing of the left / lead thigh like propping a log (thing bone) against the cabin door of the left / lead pelvis so it won't swing open in the backstroke.
With the left hip prevented intentionally from rotating "open" in the backstroke (i.e., coming forward as the rear hip moves backwards), now only the pair of shoulder joints will aim to 1 o'clock as the upper torso twists open in the backstroke using the lower back muscles. But because the hips "stayed home", the "Hansel and Gretel" shoulders have the stretched muscles and tissues of the connection between the upper torso's shoulder joints and the lower skeletal hip joints to guide the shoulders back to square coming forward. That eliminates a lot of worry about WHETHER you chose the better of the two backstroke moves. With the grip pressure making the putter face stay the same as the chest, and now the hips solving or easing the problem of using the less-desirable of the backstroke moves, you can make a shoulder backstroke that has the putter "come to the inside" a bit (hands-up aiming to 1 o'clock), with the putter face simply glued to the orientation of the chest and also with a good plan for untwisting the twist between hips and shoulders to get the shoulders and chest back to "square" before impact (i.e., back to parallel to the aim of the putter face at address and the initial orientation of the chest at address). The putter face is not the problem any more with sufficient grip pressure; returning the upper chest to its starting orientation before impact is the problem, and the hips stability basically gets that done. The tension increases as the twist between stable hips and curling shoulders increases, and coming forward the tension dissipates as the twist untwists and the brain gets a very loud and clear signal that "Ah, no more twist tension means the chest is back home and the putter is SQUARE again."
Even so, unaware golfers don't know what the "critical checkpoints" of this might be and so slop it up all the time. One is WHEN or WHEN-WHERE the chest re-squaring has to get done by: answer: at least 1-2 inches before the forward stroke reaches the back of the ball. That why I teach golfers not to putt the back of the ball, but to putt to the bottom of the stroke defined at address for orientation and timing. Another is, once resquared, do you continue the upper chest rotation or what, exactly? Answer: once resquared, stay there but let the on-going linear momentum of the arms and putter as a stable unit NOW define where the upper chest moves, as then that will only move the putter face straight and square down the line slightly rising in a vertical arcing above the line of the putt with the face staying square to this line, and that putter head and hands and arms trajectory right straight across that intended line of putt will cause the shoulders to move ONLY in a vertical plane with the lead side NOT backing up at all but rising vertically as the putter head continues down the line. Basically, with the shoulder frame parallel to the aim of the putter face at address, the putter shape will only swing straight across in front of the body, which is natural and exactly all and only what you want.
Even more fundamentally, stand next to a wall and swing only your heavy arms hanging naturally off the bent torso. Just aim the fingers of each hand at each other like cradling something, and swing both arms straight along the toe line back and thru. There's not much to it, especially if all you really care about is the forward swing "up along the wall". Adding a putter to this physics doesn't change the motion much, but requires enough grip muscle tone to keep control.
The way to experience this is to set up opposite a wall with the putter squared up to the wall about 1/4 inch off the baseboard and then hold the hips steady and make a shoulder backstroke with enough grip pressure and then coming forward "get square and stay there before getting there" to the back of the ball and then let the putter swing up the wall with the lead shoulder rolling up beside the wall not pulling away from the wall.
We could go thru the armsy stroke as well, but you don't really have to because the arm pits never open until a stroke gets outside the stance. In between the feet shoulder width apart, everyone is freely and naturally and effortlessly ONLY using a shoulder stroke in which the arm pits don't change a bit. If you make an armsy stroke, just get the hands and putter face back to online / square before swinging forward into the stance between the feet. That's the armsy main checkpoint.
If you want to save a lot of trouble, reduce the armsy joint angle changes by adding muscle tone on either side of the elbows to reduce elbow angle changes in the stroke and also use a mild non-violent tempo to minimize bat opening physics. Making the muscle tone of the upper arm muscle match the tone of the forearms, which matches the tone of the hand muscles on the putter handle, gets the elbow joint stabilized a bit. It also helps if you tuck the leadside elbow inward at the hip a bit by "supinating" the forearm thumb rolling palm up to the outside of the body midline, and then rotate the forearm pronate-wise to return the thumb to the orientation that extends it straight down the handle to match the thumb print flat onto the flat of the handle's top surface -- all with a naturally hanging arm. That gets the armsiness under control and keeps the putter face in sync with the chest orientation. With the "not less than" grip pressure and structuring muscle tone in the arms, the flat thumb print matches the handle and the aim of the putter face at address to the chest orientation and controls the bat physics too. Then, you can forget the putter face and focus on making sure that in the forward stroke the chest is oriented as it was at address and stays in that orientation as the stroke goes down the line slightly rising.
GOLFER MANAGEMENT OF STROKE
The second cause of putter face change (especially opening) is golfer management of the stroke path. Golfers quite frankly have hallucinatory notions of what causes what stroke paths and what that means for face angle in the course of a stroke path. Terrible teaching makes this all much worse. Hyper-geometrical analysis of the putter face aim at each point in the stroke misleadingly implies patterns of movement that don't do anything like what golfers simplistically think they cause. Training aids have golfers tracing shadow projections of 3-dimensional pathways as if moving on the shadow in a 2-dimensional plane on the ground where the shadow lays will accurately make the 3-dimensional movement in space. Just stupid and crazy and weird and not close to being good geometry or sound movement in good geometry.
Do NOT putt "on an arc". Then you will think like Stan Utley wrote, and either completely mess it up trying to chase head-shadows or you will not have the vaguest clue what you are actually doing and how you do it. Also do NOT pay any attention to stroke monitors; they are poison because they don't have anything to offer about why or how things get the way they get, and just worry you to death about getting some pictures and numbers on a computer to come out looking like some nitwit wearing a lab coat thinks would make you look more like other golfers who aren't great putters and who also don't know how and why they do what they do.
Instead, pay attention to your body and swinging the bat in control to return the putter face square and online and centered on the same line you aimed at address. Then the know-how will dawn on you.
Okay, ready to answer YOUR particular stroke problem.
You write: "I bought a laser device that hooks to my putter to show where I am aiming. At address I am aimed at the hole but in the back stoke the putter face swings open than remains open in the follow-through. Even when I take it straight back keeping the face square it still wants to swing open in the follow-through. On a 10 foot putt my putter face is aimed approx. 6 inches to the right of the target at impact."
You are paying attention ONLY to the putter face and not to the body that CAUSES it to move or aim in any direction. You are also using the passive voice, which is death in science, because it conceals the causal relationship that sticking to an "active voice" reveals. You write that "when I take it straight back keeping the face square it still wants to swing open in the follow-through". Follow the "it" in your language, because that is your problem in understanding what YOU are doing. You wrote, "it still wants to swing open in the follow-through". "It" doesn't want to do anything; it's dead; it doesn't "do" anything at all; it's a putter; it's dead. You move your body in a certain way; that moves the putter. That's all. So what way is that?
It seems to me you aren't really coming to grips either with how you move in the backstroke and where that ends up with your body orientation and putter face at the top of the backstroke, nor with your movement in the forward / thru stroke. Those two movements CAUSE the putter face to move in specific orientations.
The first of the two patterns you describe the face opens in the backstroke. This is either too little grip pressure or using the lower back muscles to rotate the spine and hips so the hands-up arms would aim to 1 o'clock. That COMBINATION of openings can certainly result in a putter face opening 6 degrees, some from too little grip and inertial bat swinging, plus some from hip rotation carrying the shoulder / chest alignment open. Light grip alone would not normally account for 6 degrees of face opening in the span of a 10-foot stroke size. If that happened, you would miss 10-footers 12-13" right of the center of the hole or 10" wide of right edge from only 4 steps away. But in the forward stroke, why wouldn't this naturally resquare? Nothing naturally closes in a putting stroke, even if the stroke path is curving along an arc -- the opening of the putter face will get worse unless you prevent it, and nothing will un-open a putter face except extra effort to get rid of the openness by closing the face deliberately. It doesn't happen any other way. Because you're not aware of the hip rotation in the backstroke and the need to re-rotate the hips and you're not aware of the face opening in the too-light grip and how much that requires to get un-opened going forward, the face stays open to impact, and there you are. This pattern requires more grip pressure at address and steady thru the stroke PLUS a stable left hip to control and return shoulders to address aim so that the putter face comes back to square by the bottom of the stroke before impact.
The other movement pattern had the putter face kept square all the way to the top of the backstroke. Your keeping the putter face aimed on line to the top of the backstroke looks to me like you don't understand how putterface path and face angle management is getting done, and that is ending you up in an unnecessarily confused posture at the top of the backstroke. The forward stroke movement has to start from the top of the backstroke posture, and you don't have a good bead on what that is. When you "carefully" make sure the laser stays aiming online all the way to the top of the backstroke, and ignore exactly what joint changes are going on while watching the laser aim, almost everyone has the right hip rotating back away from the start line. That top-of-backstroke ending posture has the hips aiming to the outside of the line. The forward move from that posture pulls the right rib cage down at the right hip. In this move the center of gravity of the body inside the lower abdomen makes a little curl-back in the backstroke then the forward stroke juts the right hip forward as the inner oblique tugs rib cage and hip together. In so many words, that's a dead push CAUSED by the hips opening in the backstroke and then STAYING OPEN. Your hips carried the shoulders with them in this opening, and you forward stroke simply goes straight along the shoulder orientation, so you don't know what the problem is. That's because you're watching the laser and not your joint orientations. You can almost never, ever rotate the hips open without carrying the shoulder alignment open also; to do otherwise is positively weird and highly artificial and always noticeable. Not noticeable, but quite natural and hidden to open the shoulder alignment with a small hip rotation open in the backstroke.
The only other possible explanation is your grip is the grip of a ten pound weakling, because you accepted some guys advice to putt with "sensitive fingers" and you lost control of the bat out of sync with your chest orientation.
If the putter face ever gets "open" in relation to the plane of the chest or the plane of the forearms, "it" won't ever close itself, and in fact "it" is subject to inertial physics that will make matters WORSE open in the forward stroke because the tip of the bat does not want to go forward since it's heavy, and failing to bring it forward "against its will" with sufficient manly grip pressure will CAUSE the tip of the bat and the face angle of the putter to get WORSE in the forward stroke. So it's barely possible but unlikely that your hips did not rotate open but you managed your grip pressure in the backstroke while watching the laser instead of your body, but then in the forward stroke, you went back to the sissy grip and the bat opened only in the forward stroke.
That's a bit unlikely.
To end up aiming the face at impact on a 10-foot putt with a total backstroke length of perhaps 12-15 inches and a movement of the right shoulder in the backstroke rising no more than 2-3 inches at most, and a forward stroke rocking the lead shoulder from 2-3 inches below the starting address position to 2-3 inches above the address position for a total "rock" of 4-6 inches, at a tempo and pace usual for a ten-foot putt (not too violent usually), there is not likely enough inertial opening with the usual "light" grip pressure to open the face 6 degrees in the forward stroke. Most people have the habit if not the awareness of stabilizing the "feel" in the palm and fingers of the right hand in the forward stroke, which only insures that not much further opening than has already happened to the top of the backstroke now happens in the thru stroke. So that usually minimizes the forward-stroke inertial opening -- keeping the sense in the hands of steady contact with the handle inside the right palm and fingers means not more opening coming forward. But that doesn't prevent the backstroke opening from a girly grip swinging a bat meant for a man losing control of the putter face.
For a putter face to "open" six degrees means the toe of the putter rotates on the axis of the putter head horizontally away from the target X inches depending on the diameter of the putter head made to rotate in a circle of 360 degree. If the putter toe is say 3 inches out from the axis of rotation of the putter head in a circle (depends upon the hoseling), then the diameter of that circle is 6" and the circumference in 360 degrees is 6" time pi, or 18.8". Per degree that is 0.0523" per degree of toe opening, and there are 6 degrees of opening so the toe would swing open along a little arc 0.314" in length. That quite a bit of loss of control in the inertial forces coming forward -- more than likely given the size of the forward stroke, it's likely low-level of violence, and the likely steady feel in the right hand.
On the other side, if you look at the hip rotation, the hip are a little less wide than the shoulders, perhaps 14" apart and each hip (top of pelvis really) perhaps 7" from the center of rotation. That circle is 14" in diameter and has 14" times pi = 43.96" (just say 44") in 360 degrees and 0.122" per degree and 6 degrees open is done by rotating the hips 0.73" along the arc. So which do you believe -- 3/10th of an inch of putter toe opening in the forward stroke not noticed in the hands or 3/4th inch rotation of the hips not noticed in the backstroke? I'm betting on hip rotation in the backstroke.
The bottom line is forget the laser and pay attention to the joints that control the bat. All you have to do is face the line of the putt like a wall, grip the putter securely, hold the left hip in place, tug the left inner oblique to send the side of the rib cage down at the middle of the left foot, and then swing up along the wall square and online and centered at impact. If something comes unglued or is miss timed, pay attention to the joint pairs -- they moved the putter. The golfer is the only thing moving.
Putting Coach and Theorist