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Bowling Ball Drilling Layout Terms

If you are considering purchasing a new bowling ball and are already pondering how to have your ball drilled, then there are a few common terms you will hear in pro shop circles pertaining to a given drilling layout.

It can he useful to understand just a bit about these technical terms without getting too buried in understanding each detail related to the science of bowling balls.

Here are some of the terms relating to ball drilling and given layout the pro shop professional must consider in mapping out your new bowling ball:

Drilling Layout - A bowling ball drilling layout is simply the map of where your pro shop pro will drill gripping holes into your new bowling ball. By drilling holes into the ball, weight will be removed from the ball which will cause a slight weight imbalance toward a given side of the bowling ball.

Your pro shop professional can use this imbalance to your bowling advantage and influence the ball motion as it travels down the lane.

Positive Axis Point (PAP) - The point on the pocket side of your bowling ball at the end of the axis of rotation while your ball is in motion is referred to as your bowling ball positive axis point.

When your bowling ball is delivered, the ball will revolve around an axis known as the axis of rotation. At the ends of the axis of rotation are the PAP and the NAP (negative axis point). The PAP is the one point most important in deciding on a drilling layout and ultimately in achieving a desired ball motion.

Bowling Ball Pin Locator - The “Pin” locator is best defined as a polyester or urethane stem which is positioned in the weight block to hold the core in place as the coverstock is poured into the ball mold during the manufacturing process.

This “Pin” represents the top part of the weight block and is usually represented by a colored dot on the surface of the ball.

Bowling Ball Top Weight - Bowling Ball top weight is a term used to refer to the weight difference measured from the top half of a bowling ball compared to the bottom half of the given ball.

The United States Bowling Congress (USBC) states that a bowling ball 10.01 pounds or more may have not more than three ounces difference between the top half of the ball (finger hole
side) and the bottom half (side opposite the finger holes) after the holes are drilled.

Bowling Ball Mass Bias - The part of a bowling ball in which the internal mass of a bowling ball is closest to the outside edge of the coverstock is commonly referred to as Mass Bias. This does not include the Pin.

Bowling ball mass bias helps control the shape of a given ball reaction on the back end of the lane. When the mass bias marker on the ball surface is moved to different locations, it will affect your ball reaction.


These terms are used in planning stages by pro shop professionals when choosing drilling layouts which can be options to help their customers. The entire point in choosing a given layout is to gain a desired ball reaction based on the bowling ball construction and it’s own reaction characteristics.

Knowing or being a little familiar with the pro shop terms we hear relating to bowling balls can be both informative and help you gain insight into the pro shop technical planning needed when choosing a drilling layout or when choosing a new bowling ball.

Knowledge is key but don’t become obsessed with too much technical data about bowling balls when so much depends on your shotmaking skills and lane conditions.