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USGA New Scoreline Update


While it’s still somewhat early in the season, analysis of a number of PGA Tour statistics for the first 13 events of 2010 are starting to show that the USGA’s desire to increase the penalty for hitting the ball in the rough by changing the shape of scorelines is not working out like the USGA planned.

Golf World magazine, the weekly consumer golf publication owned by Golf Digest, has been keeping track of several statistical categories from the PGA Tour for 2009 vs. 2010 which have been selected for analysis to be pertinent to the performance of the new scorelines. The statistical areas for comparing the results of the pre- to post-new scoreline rule implementation that were chosen by Golf World after consultation with equipment experts throughout the golf industry are as follows:

1. Driving Distance

2. Driving Accuracy (percentage of fairways hit)

3. Proximity to the Hole for shots hit from the rough from 50 to 125 yds

4. Proximity to the Hole for shots hit from the rough from 125 to 150 yds

5. Scrambling Percentage (percentage of times the player is able to get the ball up and down when missing the green in regulation)

6. Scoring Average



Through 13 PGA Tour events in 2010 vs 2009 the statistics compare data on the same exact courses for each event for both years.




In viewing the statistics for Driving Distance, the 4.9 yard drop in distance coupled with the slight increase in fairways hit this year seems to indicate that some players may be hitting less club off the tee in an attempt to avoid the rough. However, the most compelling data for old scoreline vs new scoreline performance is the proximity to the hole for shots hit from the rough.

From 50 yards to 150 yards, it appears that tour players are hitting the ball slightly closer to the hole with the new groove irons and wedges from the rough. In addition, because most tour courses have significant rough around the greens, this year’s much higher scrambling percentage seems to indicate the pros are not finding it more difficult to get the ball close enough to the hole with the new scoreline clubs to be able to make the putt when they miss a green.

The USGA's intent when they adopted the new rule was to create new scoreline guidelines which would prevent the players from being able to spin the ball as much for shots hit to the green from the rough. The USGA felt if the new grooves did not generate as much spin from the rough, players would not be able to hit the ball as close to the hole on approach shots hit from the rough or on chip/pitch shots.

While these statistics are only from the first three months of the 2010 season, the numbers are from over 5000 rounds of golf, thus making the data reasonably significant for monitoring the effect of the new grooves on performance. In addition, the data is from exactly the same golf courses for the first 13 events in 2009 vs 2010, another point which makes the data pertinent.

Golf World editors have told TWGT that the USGA has been made aware of their statistical findings. The USGA has indicated it would not comment on any statistical comparisons related to the use of the new scorelines in competition until after the US Open in June.

What seems to come forth from this information is the fact that even if you give clubs with scorelines that generate less spin from the rough to the best players in the world, they will adjust and will still be able to get the ball close enough to the hole to not affect their scoring. While the USGA’s primary goal was to enact the scoreline change to increase the penalty for hitting the ball in the rough, it appears they did not take the tour players’ incredible skill into account, and as a result, the new grooves are not having the effect the
USGA intended.

As a result, we’re all staying tuned to hear what the USGA has to say when they offer their first official comment on the new scorelines following the US Open in June.


What Do the New Scorelines Look Like?

Clubmakers are aware that there are two specific changes in scoreline design brought about by the USGA’s new rule. First, the new lines must have a smaller groove area, and second, the top edge radii of the grooves must be increased, or made to be more rounded than before.

The maximum allowed groove area is 0.0030 in2/in and the top groove edge radius must be 0.010” R (0.254mm R) with a tolerance up to 0.011” R (0.279mm R). Within these dimensions, the previous maximum allowed groove width of 0.035” (0.889mm), the groove spacing limits of no less than 3 times the groove width, and the maximum allowed groove depth of 0.020” (0.5mm) must also be observed for the scorelines to be ruled conforming.

In the USGA’s groove conformity testing, allowances are made for slight deviations. For example, if 50% of more of the grooves are wider than 0.035” or if any one of the grooves is wider than 0.037”, the club is non conforming. If 50% of the grooves are greater in depth than 0.020” or if any one of the grooves is deeper than 0.022”, the club is non conforming.

Similar slight tolerances also exist for the spacing between the grooves, the consistency of the groove widths on the same clubhead, the groove area, and the top edge radius which are much too exhausting and complicated to spell out in detail in this article.

Because we have recently completed the conversion of our 555C, 555M and 560MC forged iron models to now be manufactured with new grooves that are officially ruled by the USGA to be conforming to the new scoreline rule, we thought clubmakers might be interested in actually seeing what the profile of one version of conforming new scorelines looks like when compared to a conforming version of the old scorelines.

In the following illustrations, the groove profile tracing on top represents the old scorelines on our forged irons while the lower profile drawing represents the new scorelines. As you view these, keep in mind that we do all of our clubhead design work in metric dimensions. That’s why above when we outlined a few of the pertinent groove dimensions, we translated the Imperial measurements of the USGA to metric equivalents. While we do perform the groove analysis tracing for every scoreline on the face of each head number, for ease of illustrating the difference we have reduced the drawings below to show just a handful of the total number of grooves on the clubface.







In viewing the differences between the profile drawings of the old and new scorelines, focus on the groove depth and the top edge groove radii. Groove width and separation are the same for both versions with very reasonable tolerances. As you can see, we still are making our conforming new scorelines to be U-shaped, which is completely acceptable as long as the groove area is reduced and the top edge radii are increased to be within the new groove guidelines.

In conforming to the required reduction in groove area, you can see we reduced the groove depth from an average of 0.44mm to an average of 0.41mm. Since our groove depth spec was well under the 0.5mm maximum, we did not have to reduce groove depth ver much to bring the groove area within the new rule limit. By the way, this is before paint filling is put into the grooves, so golfers who desire the maximum groove area on the to channel away moisture should remove the paint filling from the grooves!

The biggest change in the old to new grooves has been on the top edge radius. On the old scorelines, the top edge radius of the grooves averaged 0.13mm (0.005”) Radius while on the new grooves it is 0.23mm (0.009”) Radius, which puts it within the new requirement of 0.010” Radius.

A lot of work goes into re tooling clubheads with loft of 25° or higher to conform to the new scoreline rule. While TWGT is pleased to be finished with this change on our three forged carbon steel iron models, after viewing the performance statistics from the first 13 tournaments on the PGA Tour chronicled in the previous article in this month’s ETECH, we can’t help but wonder why we had to withstand the cost and time required to do this.