Whether you have read it in a marketing campaign or noticed them yourself, tungsten and lead weights are becoming more and more common.
The full answer is complicated.
However, it can be summed up as a way to improve the Moment of Inertia (MOI) of a golf club.
Moment of Inertia
What is the Moment of Inertia (MOI)?
The scientific answer would tell you that it is the torque required to change the velocity of a mass about an axis.
This answer certainly sounds cool, but if you are like me, you were probably left still confused.
In golf, the goal is to strike the ball in the exact sweet spot of the club with the face precisely perpendicular to the trajectory of the ball.
In practice, this is nearly impossible to do. You will never strike the ball with perfect alignment.
The club face will want to twist sending the ball in the wrong direction, even if you are just a little bit off.
Luckily, golf equipment manufacturers know this. Therefore, golf clubs are now being engineered to reduce that twisting motion.
The physical concept that they utilize is MOI.
The goal is to get the mass of the club as far away from the axis of rotation.
In THIS video you can see the drastic effects that this can have.
The red wand in the video has its mass close to the axis of rotation and can be accelerated and decelerated very quickly.
In contrast, the blue wand has its mass on the edges, which is a higher MOI. The blue wand is much harder to spin and stop from spinning.
Golf manufacturers strive to have golf clubs behave like the blue wand.
As previously stated, golf manufacturers want to manipulate the MOI of a golf club to make it harder to twist.
This is achieved by placing the weight as far away from the axis of rotation as possible.
On a golf club, this location is as far away from the face as possible.
Hence, almost all modern drivers and fairways have tungsten weights added in the location circled in Figure 1.
Adding weight makes the club more difficult to swing quickly, but it makes the club much more resilient to twisting and therefore forgiving
Figure 1: The tungsten weight located away from the face works to reduce twisting of the club.
Many putters utilize a similar concept and try to place weight as far away from the face as well.
This is why so many putters have long sections leading away from the face.
Many putters today even place tungsten weights such as the TaylorMade Spider X putter visible in Figure 2.
This club functions identically to the design weighting elements of the driver.
Figure 2: Two tungsten weights increase the MOI and make this putter much harder to twist
Irons and wedges operate in much the same way as well.
Tungsten inserts and hollow cavities are used to shift weight to the heel and toe and away from the face.
This increases the MOI of the clubs and makes them more forgiving.
Historically, this is one of the reasons blade style irons are deemed hard to hit.
The MOI on most blades is relatively small, which makes them prone to twisting during the swing.
Most of these added weights are made out of the metal tungsten.
This is because tungsten is very heavy.
Lead technically weighs more per atom than tungsten. However, tungsten is more dense.
Tungsten is also a very durable metal and manufacturers do not worry about tungsten weights being easily damaged like soft lead ones would be.
The only drawback is that tungsten is much more expensive than lead.
These tungsten weights are one reason why golf clubs have increased in cost rapidly in the last couple decades.
All in all, weights have made their way onto every golf club you could put in your golf bag.
This is ultimately in order to increase the moment of inertia (MOI) of a golf club and reduce its ability to twist.
These weights are also made out of tungsten, due to its durability and high density compared to other heavy metals.
If you have any questions, leave them in the comments below.