Tech Talk

What is torque?

Torque is the rotary equivalent of a force. It is twisting force.

Example: If you pull or push on a door handle, you are exerting a force.
If you turn a doorknob, you are exerting a torque.

How does torque happen? Every object has a point around which it will pivot. Some objects, like our doorknob, have an obvious pivot, an axis through the door. But an object that isn't tied down (like a putter) has its center of gravity (CG) as the pivot. The CG is the "balance point" of the object. A force applied to the object that doesn't go through the CG will turn the object around the CG -- hence it applies a torque. The larger the force, the more the torque. The further from the CG the force is applied, the more the torque.

What is torque in a putter?

Torque in a putter is the twist that opens, closes, or squares the face. Your hands can and do apply a torque to the putter. They twist it around the axis on which the hands grip the club. If the torque is the right amount, considering the stroke and the design of the putter, then the face will reach the ball square to the target line. But incorrect torque results in an open or closed face at impact.

Is there a difference between the hand axis and the shaft axis?

Before we go any further, let's pay attention to the notion of a "hand axis". Remember, the hands apply the torque that turns the putter head, so the axis they twist around matters!

The hands are grasping a cylinder more or less, the putter grip. If the axis of the grip is the same as the shaft axis -- the usual case -- then we can simplify the example by just looking at the shaft axis. But if the axis of the grip cylinder is tilted from the shaft axis, it is the grip axis that matters -- not the shaft axis. And grips like that do exist. For instance, there are pistol grips that aim the hand axis more to the toe than the shaft axis is pointing. Or the grip may cant forward in order to accommodate a golfer's forward press. When that happens, the axis that determines the torque is the hand axis, not the shaft axis.

For the remainder of this Q&A, we will discuss the simple situation where the grip is concentric with the shaft axis. Just remember that a tilted grip will change the axis we need to consider.

Are putter face orientation and torque during a putting stroke related?

They are absolutely related! That is the only reason to talk about putter torque at all. Let's look at what hand torque has to do in order to create square impact -- and it will vary with the putter's design and the golfer's putting stroke.

Why should the hands need to exert any torque to square the clubface? That depends on where the hand axis crosses the putter head, compared to where the CG of the putter head is. Let's look at the important features of putter design and what torque each one demands of the hands. (Reminder: we think about the shaft axis because it is easy to visualize. But if the hand axis is not the same as the shaft axis, we should be thinking about the hand axis instead.)

  • CG behind the hand axis - If the CG is behind the hand axis, then the putter will try to fall to an orientation where the face is open. The hands will have to exert a torque to close the face in order to get it square at impact. This is not just for the CG in a straight line directly behind the axis; it is true any time the CG is fruther from the target than the axis is. This is a static property due completely to gravity; the clubhead does not have to be accelerating for this to happen, though it is also a component of the torque during acceleration.
  • CG toward heel or toe from the hand axis - If the CG is toward the toe, then the putter will tend to open its face during the through-stroke acceleration. Conversely, if the CG is toward the heel, then the putter will tend to close its face during the through-stroke acceleration. If the face is to be square at impact, then the hands will have to apply a torque to the grip to oppose this tendency.
  • Zero torque - A zero torque putter is designed so the hand axis goes through the CG of the putter head. If that happens, the hands shouldn't have to apply a torque in order to square the face. In fact, any torque the hands happen to apply can move the face away from square.

But wait! There's more. It's not just about the putter design. The stroke itself can also require torque from the hands in order to square the face. If your stroke opens the face in the backstroke, then the hands will have to provide torque to twist the face back to square on the through stroke.

What is more important to the success of a putt: putter head path, face angle, or centered strike at impact?


Face angle is by far the most important. It is 10 to 20 times more important than head path in determining the direction of a putt. (Distance is less influenced by head path and face angle.) How about an example with real numbers. Let's talk about a 10-foot putt.

  • A face that is 5° open or shut, with a square path, will miss the hole by about 8 inches.
  • A path that is 5° right or left, with a square face, will be only 1 inch off-line at the hole, easily dropping in.

Hitting the ball on the "sweet spot" of the putter is more about distance, though it does have a small influence on direction. The design of the putter can minimize the effect of an off-centered hit. Many modern putters have heads with a high moment of inertia (MOI). The MOI is a measure of how much the mass placement resists torque -- how much it keeps the head from twisting even if an off-center strike creates some torque during impact.

Does face milling affect the outcome of a putt?


A milled face can do two good things for the outcome of a putt:

  1. There was a study published in 1992 showing that a cast putter head (very common then) was not as flat as it looked. In fact, it was so un-flat that 20% of the putters tested were likely to miss a 10-foot putt just because of an uneven face. Milling the face flat cures that.
  2. A flat but smooth face sounds like the ideal solution, but it isn't if the ball gets wet. Any water between the ball and the face will result in a very unpredictable putt, both in speed and direction. But if you mill the face flat but coarse, It adds the equivalent of grooves that channel the water away and allow face-to-ball contact. That will stabilize the putt in wet conditions.

What correlation is there between putter head loft and the roll of the ball?

Putter loft imparts two things to the ball: launch angle and backspin. With typical putter lofts (1° to 4°) there isn't much spin, but the launch angle can be noticeable. This can be good or bad, depending on what kind of green you are putting on.

  • A fast, tour quality green -- say, 10 or more on the Stimp scale -- calls for a putter with a low loft. It gets the ball rolling faster.
  • A slow, even shaggy green needs a little loft to get the ball on top of the grass. Too low a loft lets the grass mess with the initial movement of the ball, which can affect both the speed and direction of the putt.

The same is true for using a putter from the fairway or fringe. You will get more predictable results with a higher loft.

Why is “shaft lean” an important component  of putter fitting?

We just saw that the correct loft is important to impart a good roll. Well, shaft lean at impact affects the loft at impact. Forward lean directly subtracts from the loft, and backward lean adds to the loft.

For instance, if you have a 2° forward loft at impact:

  • Your 2° putter for fast greens turns into a 0° putter, not enough loft for a clean roll and dangerously close to a negative loft that pushes the ball into the ground.
  • A 4° putter, on the other hand, turns into a 2° putter. In other words, a putter that seems to be for shaggy greens becomes ideal for fast greens.