Surfaces are often critical because they can define important functions such as:
• How well paint or coatings may adhere.
• How much contact area exists between two mating surfaces.
• How well a specific type of lubricant will be held in place.
• How the surface will be affected by load, speed or direction of motion.
• How the surface appears to the human eye.
• How much a golf ball will spin (example to follow).
Whether measuring a standard roughness parameter or conducting a full waviness or contour analysis, surface measurement is becoming increasingly important to ensure proper performance. As noted in that last bullet, this is affecting even the games we play.
New rules being applied to the faces of golf clubs show just how important an engineered surface can be. Using a club that does not meet proper surface finish and contour specifications could cost a player the bragging rights of the Club Championship or maybe a few hundred grand in a professional tournament in the near future.
In the last few decades, dramatic technical changes in golf clubs have made the game a little easier to play. It has been demonstrated that new club head and face designs help players hit the ball farther and straighter. They also make it easier to hit the ball out of the rough.
In response, the United States Golf Association recently announced revisions to the Rules of Golf, placing new restrictions on the cross-sectional area and edge sharpness of golf club grooves. The revisions are designed to restore the challenge of playing shots to the green from the rough by reducing backspin. The initial focus of the new rules will be competitions involving highly skilled professional golfers—most golfers will not be affected by these rules.
As implemented, the rules change the cross-sectional area of grooves on all clubs, with the exception of drivers and putters, and limit groove-edge sharpness on clubs with lofts equal to or greater than 25 degrees—generally a standard 5-iron and above.
After many detailed experiments on various grooves, which ranged in shape from a V to a U, a new standard profile was established. Once defined, this new groove had to be qualified. Tolerances must be placed on the profile, and a way to measure it must be determined. This is the aspect in which surface gaging and profiling become important.
In typical metrology practice, the goal is to analyze a measured data set to determine whether a characteristic is within tolerance. In these cases, the nominal dimensions and the tolerances are both specified.
In the case of the golf club profile, this information is not rigidly specified. Rather, the goal is to determine “conformance” to the rules. According to the United States Golf Association (USGA), transition points from the “lands” to the “grooves” are determined by 30-degree contacting lines. The width, depth, groove area and spacing to adjacent grooves must be determined.
To qualify, a club face must pass the following conformance checks:
• Groove width.
• Groove depth.
• Groove separation.
• Groove consistency.
• Area width plus separation.
• Corner radius.
As these rule changes affect both the players and the manufacturers, it becomes important that manufacturers test club designs for conformance to the Rules of Golf. While the testing for conformance is very detailed, today’s surface-profiling systems can speed the process with automated routines that analyze all the required characteristics. The final step, determination of conformance, is also complicated due to the nature of the rules, but this, too, has been automated in an easy-to-use program.
Clubs manufactured today are in conformance with the new design. You can still use your old ones, but if you want to make a living from them, you will need to make the switch by 2014.