The Test, the Machine, and the Buried Line
The Professional Bowlers Association has a rule against soft bowling balls, and the United States Bowling Congress has a machine that is supposed to catch them. The machine is a durometer. It presses a steel needle into the surface of a ball and reads back a number. Below 72 on the Shore D scale, the ball is illegal. Above it, the ball is legal. For fifty years, that number has been the line between a fair game and a cheated one.
The line is real. The machine is real. What almost nobody outside the testing room has read is the written procedure that tells the operator what to do when the machine says a ball failed. That procedure is a public document. It is called SOP Ball 5, and buried in the middle of it is a single instruction that quietly hands the close calls to the people the test is supposed to catch. The United States Bowling Congress does not put this in its press releases. When a ball reads below the minimum, the procedure does not end there. The ball gets tested again by a second operator. If the second operator’s reading passes, the procedure says the manufacturer is given the benefit of the doubt and the ball passes. One fail and one pass does not average out. It does not trigger a third test. The tie goes to the ball company—in writing, by rule.
Why the Line Sits at Exactly 72D
That line matters because of how thin the margin already is. In the early 1970s, bowlers were soaking balls in solvents to soften them. A softer ball left a bigger footprint on the lane. More ball touching the surface meant more friction and more hook. The American Bowling Congress correlated footprint to hardness on a Rex durometer and found that above 72, the footprint barely moved. Between 72 and 70, it started to grow. Below 70, it grew fast. So they drew the line at 72.
The gauge maker, Rex, publishes the durometer’s accuracy at plus or minus two points. Setting the limit at 72 kept the true reading safely above 70—the point where the footprint actually changed. The problem is that everything else about the measurement is fragile. Temperature moves the number. So does humidity. So does the exact spot on the ball where the needle lands. So does the color of that spot. The United States Bowling Congress requires the ball to sit between 70 and 77 degrees Fahrenheit for at least 24 hours before testing, because a warm ball reads soft. They take 10 readings on 10 different locations and average them, and on a multi-color ball, they require readings in each color because a single reading means almost nothing. The whole apparatus exists to wrestle a stable number out of an unstable measurement.
The Needle Polish Problem
There is a wrinkle the bowlers had been complaining about for years before the United States Bowling Congress wrote it down. Testing a ball that has been polished leaves residue on the needle. The next ball reads off, because the needle is dirty. A contaminated needle can fail a ball that is actually legal, or pass one that is not. For most of the durometer’s history in bowling, there was no written rule telling operators to clean the needle between balls. That rule got added in November of 2022—revision 6 of SOP Ball 5. The instruction reads that after testing a polished ball, the indenter should be cleaned, and a sanded ball should be measured ten times to clean the needle. It is a sound procedure. What is worth noticing is the date: the United States Bowling Congress formalized the fix for needle contamination only after the equipment controversy that consumed the sport in 2022 had already blown up in its face.
The Creating the Difference Study
An independent testing outfit called Creating the Difference ran its own study during the controversy using the United States Bowling Congress procedure on a durometer stand. Their findings read like a list of all the ways the number can move. Color changed the reading. On the same ball, the yellow portion tested harder than the purple. Sanding the ball did not change its hardness at all—which contradicted what a lot of bowlers assumed. When they took one ball and deliberately softened it from about 73.8 on the Shore D scale down to about 64.9, the ball that had been twitchy and unforgiving suddenly gave the bowler five boards of room to miss and still hit the pocket. Nine points of hardness was the difference between a ball that fought you and a ball that covered for you.
But the same study found something that cuts the other way: none of the manufactured Purple Hammers they checked tested soft. Multiple batches did. Run carefully, the test could see the difference between the two. The needle was sensitive enough to catch a real manufacturing gap—which makes the written rule stranger, not more reasonable. An instrument that can tell a soft ball from a legal one is governed by a procedure that still hands the tie to the company that made the ball.
In March of 2022, the United States Bowling Congress revoked approval of all Purple Hammer bowling balls manufactured by Ebonite International in 2016 and 2017. Some of those balls had been produced below the 72D minimum. The USBC’s investigation found out-of-spec equipment had been used in sanctioned competition for two years before anyone checked.
The Black Curtain and the Inconclusive Finding
The clearest example landed on the most decorated bowler alive. In the middle of the fight, at the 2022 USBC Masters in Las Vegas, the United States Bowling Congress asked to test the equipment of Jason Belmonte—the all-time leader in major championships and the most decorated bowler of his generation. He agreed to the test. Then he described what happened. The testing, he said, was done behind a curtain, and he was not allowed to be present to watch his own equipment being measured. He posted about it publicly. The United States Bowling Congress fined him $250. The violation was a conduct rule covering electronic media. Their position was that his post put the organization in a bad light.
Belmonte’s response was direct: if what he described was exactly what happened, and he had not exaggerated or lied, then maybe the problem was not that he talked about it. Maybe the problem was the thing he described. That is the moment the buried detail stops being a line in a document and starts being a pattern—a test fragile enough to need a black curtain, a fine for the man who said the curtain was there, and a written rule sitting in the procedure the whole time that resolves a split reading in favor of the ball company.
When the United States Bowling Congress finally concluded its Purple Hammer investigation, the official finding was not guilty. It was not innocent. The finding was inconclusive. No one interviewed provided evidence the balls were knowingly produced under spec. The organization prohibited the balls anyway, on concern rather than proof, because proof was exactly what the test could not deliver.
Twenty Years Nobody Was Checking
There is a longer silence underneath all of this. The American Bowling Congress wrote the 72D rule in the 1970s. The Professional Bowlers Association set its own stricter line at 75D. For decades, manufacturers built balls at 78 to 80D just to stay clear of trouble—so a ball that actually failed was rare. Then, in 2001, the Professional Bowlers Association stopped testing for hardness at all. The organization concluded it was no longer a meaningful enforcement measure, given how rarely anything failed. For roughly the next twenty years, the rule against soft balls existed on paper while nobody was checking. The inspection was not behind a curtain. The inspection was not in the building.
By 2025, the governing body stopped trying to win the argument over individual balls and changed the terms instead. It raised the manufacturing minimum and began removing whole categories of equipment from its premier national tournaments—including the U.S. Open and the Masters—starting in 2026. Spot-check testing continues, and the United States Bowling Congress describes it as a tool to identify potential tampering. The same durometer, the same fragile number, the same procedure that hands the close calls to the ball company. For half a century, the line at 72D has held. The machine that is supposed to defend it presses a needle into a ball, reads a number that drifts with the room and the polish and the operator, and follows a written rule that, when two readings disagree, lets the ball through. The rule against cheating exists. It always has. The loophole is in the procedure that is supposed to enforce it, and it has been there in writing the whole time.
Chapters
- 0:00 The Test, the Machine, and the Buried Line
- 1:02 Why the Tie Goes to the Ball Company
- 1:48 Why the Line Sits at Exactly 72D
- 2:30 Every Way the Number Drifts
- 3:23 The Needle Polish Problem (Fixed in 2022)
- 4:09 The Creating the Difference Study
- 5:51 The Purple Hammer and the Black Curtain
- 7:25 The Verdict Was Inconclusive
- 8:08 Twenty Years Nobody Was Checking
Sources
- USBC: New National Tournament Rules on Ball Use
- USBC September 2025 Report on Bowling Ball Hardness Governance
- USBC Final Adjusted Bowling Ball Hardness Specification
- The Advocate: Purple Hammer Controversy Coverage
- PBA Statement on USBC New Equipment Specifications (2025)