The USBC Equipment Specifications Manual states that a bowling ball must between 8.5" and 8.595" at the time of manufacture.

http://usbcongress.http.internapcdn.net/usbcongress/bowl/equipandspecs/pdfs/ESManual.pdf

Assuming that the ball was legal at manufacture, is there any rule that prevents use if the ball subsequently is made smaller that the manufacturer's specification?

A ball company has told me it's "OK" and there is nothing in the USBC playing rules about size (weight, holes, etc. are listed but not size).

Yea, I know no one checks/enforces.  I won't throw the ball if it's illegal regardless of risk getting caught.

just a guess, but I would assume that each time you resurface the ball, you make it very slightly smaller.  I know some bowlers that have resurfaced a ball so much that the logos have vanished and only the serial number remains.

I thought I remember seeing a study someone did like 5-10 years ago where they stuck a ball on a resurfacing machine for 24 hours at 150 grit and kept changing to fresh pads every few hrs and then drilled it identically to another of the same ball, matched the surfaces and see if the carry changed any.  And yes the 24 hour resurfaced ball was a couple mm smaller in circumference.

Yes it's legal to use, this has came up every now and then.

This is from a email I got when I asked the USBC this before:

Hello Al,

          Thank you for your question.  Specifications for diameter (circumference) and roundness are manufacturing specifications only, they are not for the end user or the drilled ball.  In the example you provided, the smaller ball would still be allowed for use during USBC certified competition as long as it still had the required markings (Brand Name/Logo, Ball Name, Serial Number) so the ball can be identified.  For a long time there was size and roundness requirement on the drilled bowling balls at tournaments, but those specifications have since been removed.

 

Thank you,

 

Jason Milligan

Research Technician

Equipment Specifications & Certifications / Sport Bowling

 jason.milligan@bowl.com

The Original question:

Question:

Does the rule for minimum ball size (8.500”) in the "Ball Manufacturing Specifications" (page:6 of the equip./Spec manual) and states "At time of manufacture, all balls must meet the following technical specifications"

Does it apply to a bowlers drilled ball?

Example:

Bowler has a older ball that do to shrinkage or resurfacing is below the min. of 8.5", Is it still legal for use?

or is there a rule regarding minimum size for a bowlers drilled ball?

(If so where do I find it in the rulebook/manual?)

If not, was there ever a rule? (I remember at one time they used min/max rings at the Nationals tournament to check ball size at check in)


Thank you

Al

Thanks, Aloarjr810, much appreciated!