Have you ever had a question on balance holes, thumbs holes and
indentations?
Jason Milligan from the Equipment Specification & Certifications Department
of the USBC answers some common questions below.
Q: When a bowler delivers his ball, he has the tip of his thumb in the hole drilled as
the original balance hole. Does that mean he is using a “thumb hole” and that the
original thumb hole becomes a balance hole, rendering the ball and the delivery
illegal?
A: The thumb would need to be inserted enough that the bowler can actually pick
up the ball in that manner, in effect showing he can “grip” the ball or use the hole
for “gripping purposes” for the hole to be considered a “thumb” hole and allow him
to also have a balance hole. If that is not the case, then the hole is a “balance”
hole and it just happens that his thumb tip rests on the balance hole. The addition
of another balance hole would make the ball and delivery illegal.
Q: Have you ever heard of a ball being delivered by a bowler using the tip of their
thumb only?
A: Tip of the thumb only, I have not heard of that grip being utilized. I have seen
bowlers remove their fingers form the holes and just use the thumb for spare
shooting, and that is allowed.
Q: Is there such a grip?
A: I don’t believe so, no way to hang on to the ball that way.
Q: What is an indentation?
A: Indentations were popular for early no thumb bowlers and for people who had
physical limitations due to injuries or disabilities. An indentation is severely pitching
the hole in a way that the drill bit only grazed the side of the ball creating an
indentation or channel for the digit to lay in.
Q: Can a bowler have a thumb hole 4mm deep and if so, is that an indentation or a
hole?
A: A hole drilled 4mm deep is still a hole, not an indentation.
Q: If there is an indentation in your ball, can that ball have a balance hole as well?
A: For gripping hole allowances, we consider a gripping hole and an gripping
indentation as the same thing. That is why you are only allowed to have up to five,
and all for the digits on one hand. For that reason, I would say you can’t have an
indentation for your thumb and a balance hole.
RULE 603 BALL DRILLING SPECIFICATIONS
Holes
The following limitations will govern the drilling of holes in the ball:
1. Holes or indentations for gripping purposes shall not exceed five and shall be limited
to one for each finger and one for the thumb, all for the same hand. The player is not
required to use all finger holes in any specific delivery, but they must be able to
demonstrate, with the same hand, that each gripping hole can be simultaneously
used for gripping purposes. Any thumb hole that is not used for gripping purposes
during the delivery would be classified as a balance hole.
2. One hole for balance purposes is allowed and it must not exceed 1 ¼ inch in
diameter.
3. No more than one (1) vent hole to each finger and/or thumb hole is allowed and
should not exceed ¼ inch in diameter.
4. One mill hole for inspection purposes is allowed and should not to exceed 5/8 inch
in diameter and 1/8 inch in depth.
Balance
The following tolerances will be permissible in the balance of a bowling ball used in
TBA competition: Refer to Rule 127 for the penalty for bowling with a ball that is found
to be illegal.
1. 10 pounds or more:
(a) Not more than three (3) ounces difference between top half of the ball
(finger hole side) and the bottom half (side opposite the finger holes).
(b)
Not more than one (1) ounce difference between the sides to the right and
left of the finger holes or between the sides in front and back of the finger
holes.
(c)
A ball drilled without a thumb hole may not have more than one (1)
ounce difference between any two halves of the ball.
(d)
A ball drilled without any finger holes or indentations may not have more
than one (1) ounce difference between any two halves of the ball.
(e)
A ball used without any hole or indentations may not have more than one
(1) ounce difference between any two halves of the ball.
2. Less than 10 pounds:
(a) Not more than one (1) ounce differences between the top half of the ball
(finger hole side) and the bottom half (side opposite the finger holes).
(b) Not more than ¾ ounce difference between the sides to the right and left
of the finger holes or between the sides in front and back of the finger
holes.
(c)
A ball drilled without a thumb hole may not have more than ¾ ounce
difference between any two halves of the ball.
(d)
A ball drilled without any finger holes or indentations may not have more
than ¾ ounce difference between any two halves of the ball.
(e)
A ball used without any hole or indentations may not have more than ¾
ounce difference between any two halves of the ball.
Plugs and Designs
1.
Plugs may be inserted for the purpose of redrilling the ball.
2.
Designs may be embedded in the ball for guides, observation or identification
purposes, provided such designs are flush with the outer surface of the ball.
3.
In all cases there will be no interior voids.
4.
Plugs and designs must be made of material similar to, although not exactly
the same as, the original material out of which the ball was made, and will
otherwise comply with all other specifications for a bowling ball.
5.
No foreign material may be placed on the outer surface of the ball.