The following information states the current specification requirements for all bowling balls balls used in sanctioned competition. Bowling balls failing to meet these requirements must be removed from competition.
If it is shown that the bowler had prior knowledge that his/her actions were in violation of this rule, the games in which the violation occurred is/are subject to forfeiture. In addition, the bowler is subject to dismissal from the the league/competition and suspension of membership.
A bowling ball shall be constructed without voids in its interior, be of a non-metallic composition material and conform to the specifications for weight, size and bal- ance. The use of minute reflective particles or flakes for decorative purposes shall be permitted in bowling ball material prwided such flakes or particles are made part of the ball at the time of manufacture, are evenly distributed in a uniform pattern under a transparent shell at least 1/4" beneath the surface of the ball so as to have no effect on the balance, and the total amount of such material does not exceed 1/2 ounce per ball.
The circumference of a ball shall not be more than
27.002 inches nor less than 26.704 inches, nor shall
it weigh more than 16 Ibs (no minimum weight).
The diameter of the ball must be constant.
The surface of the ball must be free of all depressions
or grooves of specific pattern, except for holes
or indentations used for gripping the ball,
identification letters and numbers, and incidental chipping
or marring caused by wear.
Holes or indentations, not to exceed five tor gripping
purposes.
One hole tor balance purposes, not to exceed 1 1/4" in
diameter.
One vent hole to each tinger and/or thumb hole, not
to exceed 1/4" in diameter.
One mill hole for inspection purposes, not to exceed
5/8" in diameter and 1/8" in depth.
The table below shows permissible tolerances in the balance ot a ball used in sanctioned competition.
A) Maximum differences between top of ball (finger
hole side) and bottom (solid side opposite finger
holes).
B) Maximum difference between sides to the right
and left of finger holes, or between the sides in
front and back of finger holes.
C) Maximum difference between any two halves of
ball with no thumb hole.
D) Maximum difference between any two halves of
ball with no finger holes or indentations.
E) Maximum difference between any two halves of
ball with no holes.
Maximum Tolerance (ounces)
+-------+-------+-------+-------+-------+
Ball Weight | A | B | C | D | E |
+-------------+-------+-------+-----------------------+
| Over 10 lbs | 3 | 1 | 1 | 1 | 1 |
+-------------+-------+-------+-------+-------+-------+
| 8 - 10 lbs | 2 | 3/4 | 3/4 | 3/4 | 3/4 |
+-------------+-------+-------+-------+-------+-------+
| Under 8 lbs | 3/4 | 3/4 | 3/4 | 3/4 | 3/4 |
+-------------+-------+-------+-------+-------+-------+
Movable devices are not permitted in a ball except
that a device for changing the finger span or size of
the finger and thumb holes may be inserted provided
it is locked into position during delivery and cannot
be removed from the ball without being destroyed.
The introduction of metal or any other substance no
comparable to the original material used in the manu
tacture of the ball is prohibited.
Plugs may be inserted for the purpose of redrilling;
ball. Designs may be embedded in a ball as guides
or for observation or identification purposes
provided the designs are flush with the outer surface of
the ball.
There shall be no interior voids and the plugs or designs
must be of similar material to although not
exactly the same as the original material out of
which the ball was made; and shall otherwise comply
with all bowling ball specitications.
No foreign material may be placed on the outer surface ot the ball.
The surface hardness of a bowling ball shall not be
less than 72 Durometer 'D'.
Extract taken from World Of Tenpin February 1995