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What Is The Radius Of A Bowling Ball Originally Posted:  07/05/2011; Updated On: 05/30/2024

If you are a new bowler or someone simply interested in raising your level of understanding about about the bowling ball and specifically what is the radius of a bowling ball, then it might help to understand some of the useful details relating to the manufacturing limits and tolerances under the guidelines of the United States Bowling Congress (USBC), the rules making body for all of bowling. To understand what is the radius of a bowling ball is to also learn a little about simple geometry and properties of a circle.

In this case, the two dimensional definition of a radius is the line drawn from the center point of a given circle (in this case, the bowling ball) to any point tangent to the outer edge of the given circle (or bowling ball). The relevance of this radius information to most bowlers really shows up with the diameter dimension of a bowling ball and how it relates to the bowling pin formations on the pin deck of the bowling lane. Before we address pin formation details, let's address a few noteworthy bowling ball specifications provided by the USBC (United States Bowling Congress) beginning with the diameter of a bowling ball.

The diameter of a bowling ball 13lbs or greater is a minimum 8.5" and a maximum of 8.595". The circumference of a bowling ball 13 lbs. or greater is 26.7" minimum, 27.002" maximum. This means that if a bowling ball is delivered on a perfectly straight line down the center of a bowling lane (on the 20 board), which is also where the center of the head pin (No. 1 pin) is standing on its pin spot located exactly 60 feet from the foul line on the pin deck, the bowling ball would make 26.67 revolutions by virtue of rolling end-over-end on the lane surface before contacting the head pin.

The radius of the bowling ball is exactly one-half the length of the diameter of the given bowling ball measured on a linear plane, or about 4.25". If two pins remain standing in the same row, such as the No. 4 Pin and No. 5 Pin in the third row of pins, it is possible for the ball to contact both pins and knock them over if the pin are in front of the No. 4 and No. 5 pins, the No. 2 pin, is not standing. The number of boards between the center spots of No. 4 pin spot and the No. 5 pin spot is eleven boards. The same holds true for an example of the No. 5 and No. 6 pins of the third row of pins and for examples in the back row of pins for the combination of the No. 7 and No. 8 pins, the No. 8 and No. 9 pins, and the No. 9 and the No. 10 pins, all positioned in the fourth row of pins.

The widest pin diameter area of 4.76" is measured 4.5" above the pin base or roughly the same dimension as the radius of a bowling ball. The radius of a bowling pin is, therefore measured at about 2.375" at the widest part of the pin. Subtracting the radius of standing pins from the centers of the No. 4 pin spot and the No. 5 pin spot (used in this example) of eleven inches would leave 6.24 inches between the pins. Since the diameter of the bowling ball is 8.5", then it is possible for the ball to contact both the No. 4 and No. 5 pins at the widest diameter point of the pins and thereby convert that "split" formation.
Another thing to keep in mind the width of one board on the lane is about one inch wide and although some pins, such as the No. 7 Pin or the No. 10 Pin, appear to be positioned on the edge of the lane, the pin spots are centered five boards from the lane edges on both sides of the pin deck. Since the lane is about 60 feet from the foul line to the Head Pin, the pins will appear to the bowler closer to one another than they actually are positioned.

The head pin is equidistant from both kickbacks and edges of the lane and is located 34 3/16" from the center of the pin spot to the pit. The overall lane width is 41.5", not including the channel measurements.

With these pin specifications and lane measurements in mind, it is easier to understand how a bowling ball is wide enough to contact both adjacent pins in the same row of such as the 4-5 pin combination or the 5-6 pin combination. A bowling ball can deflect enough if it contacts the right edge of the 3 pin to also contact the left edge of the 10 pin for the right handed bowler's "baby split." Same on the left side of the lane with the 2 and 7 pins for left handed bowlers.

Knowing a few details about bowling ball, bowling pin, and bowling lane specifications provided by the USBC will help you advance in the game by better understanding these useful dimensions as the key components in use when you bowl. always recommends that you consult a bowling pro shop professional when seeking additional information about bowling balls, drilling patterns, coverstocks, and core designs so you can make a selection best suiting your needs.

Other useful articles with good specification details posted in the "BowlVersity" section of our site which will help you understand the game are "Bowling Ball Specifications", "Bowling Pin Specifications", and "Bowling Lane Specifications." We hope you check these and other articles out sometime soon and continue to work in developing your understanding of this great game.

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