Bowling Ball Hardness Field Testing | WHY 68D IS OK TO USE IN COMPETITION

Here is the summary of the report.


USBC found urethane balls will pass the USBC specification for minimum hardness at manufacture, but then may measure below specification when heated. Balls measured immediately after use may also have measurements under specification. This decrease in hardness based on environmental factors occurred for urethane shell balls across multiple brands. 


Summary and Next Steps

Following our research on variables in hardness testing results, USBC is modifying the hardness specification. The USBC ball hardness specification is a manufacturing standard. The durometer measurements gathered by USBC in our testing facility is the standard for compliance. USBC knows

temperature affects the hardness results for bowling balls. The temperature range used for USBC’s testing will be adjusted slightly to 70-77 degrees Fahrenheit to coincide with the ASTM requirement. Additionally, balls tested for hardness during USBC competitions will have a new specification. Balls must be tested consistent with USBC’s standard operating procedures. They must be cleaned to remove oil, so the oil does not affect the hardness results by lubricating the durometer indicator needle. Since there is up to a 4-point variation between properly calibrated durometers, the field test will allow for this variation. A ball is only subject to being removed from competition as

determined by the Competition, if the subject ball hardness averages below 68D.

Here is the link to the USBC Research Report

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