Drilling Holes in Bowling Balls – Technical

 You may be at a point with your bowling skill level that you are ready to purchase your own bowling ball. In addition to thinking about size, weight, material, and color of your new purchase, you also need to be familiar with how the holes are drilled into the ball itself.

All You Need to Know About How Holes Are Drilled into Bowling Balls

One of the reasons to having your own bowling ball is that the grip is customized specifically for you. This is why understanding how the holes are drilled is important.

Hole Placement

When holes are drilled into a bowling ball, they are drilled not just anywhere and in anyway on the ball. There are specifications in the bowling world for where the holes are placed and how deep they go into the ball. Specifications relate to the type of ball you select as well as the kind of swing and delivery you have, and the action you expect the ball to perform (e.g., a straight roll down the lane versus a hook). Hole placement is part science and part art. It involves the physics of the kind of ball you will be using, the force with which you throw the ball, and the lane conditions. It is also part art in that very experienced bowling ball technicians learn about your bowling technique and what your bowling goals are, then with drilling specification knowledge, they can intuitively transfer your grip to the ball itself. This article focuses on the very basics of the drilling process.


A bowling ball’s PSA, or Preferred Spin Axis, is unique to each ball. To find a ball’s PSA, manufacturers consider its size, shape, as well as density of the interior of the ball, also referred to as a ball’s core. Each ball seeks to spin on its own axis. This is the PSA. A PSA can be weaker or stronger. Stronger PSAs are usually found in bowling balls with dynamic cores. Traditional bowling balls containing either a two-piece or three-piece core exhibit weaker PSAs. One is not better or worse than the other. Lane conditions (its surface and oil patterns) determine which type of PSA is more effective to use in your game.


In addition to understanding the PSA, good bowlers are also familiar with the PAP or Positive Axis Point. The PAP is an imaginary line that intersects the ball down the center and lies perpendicular to your specific ball track. Your ball track is the path your bowling ball takes when you throw it down the alley. After you practice, you should notice a ring on your bowling ball created by the oil from the alley. This is your ball track. There is also the vertical axis line or VAL. Like the PAP, the VAL is a line that goes through your PAP, perpendicular to your grip mid-line. That being said, the drill pattern you end up using will not change how the ball you select reacts. A ball designed to perform best with a straight roll will not be altered to perform best as a hook ball, and vice versa, just because of hole placement.

Drilling Layouts

Let’s say that you have gone through the process of selecting a bowling ball. Now you are ready to have holes drilled into your ball. Generally speaking, there are three types of drilling layouts: low RG layouts, high RG layouts, and a category known as leverages.

Bowling balls with the low RG drilling layout will roll earlier down the lane. This is an excellent layout if you throw a fastball and have strong axis rotation. In comparison, if you throw a slower ball, using a high RG layout may be in order. Leverage patterns come into play when you are bowling on heavily oiled lanes.

If you play at a very high level and/or as a professional, you might be aware that depending upon the drilling layout you choose may require that a balance hole(s) be drilled into your bowling ball. The US Bowling Congress (USBC) has rules regarding the drilling of balance holes. Balance holes (like the other holes drilled in the bowling ball) do not change the intended reaction of the ball on the lane, but can subtly tweak your ball so that it is fine-tuned to your skill level.

The Actual Grip

How you grip the ball affects your ability to throw the ball down the lane. Gripping the ball too tightly may delay your ball release; gripping it too loosely may result in the ball slipping out of your hand or being dropped on the alley itself. Beginning bowlers tend to have the holes drilled in a traditional way. In this style of grip, you hold the ball with your middle and ring fingers up to the second joint of each finger then complete the grip by placing your thumb completely into the thumbhole without bending it at the joint. With this grip, the palm of your hand should rest lightly on the surface of the ball.

As you improve your bowling game, you may consider purchasing a new ball with a new grip – one where you grip the ball up to the first, not second, joint on your middle and ring fingers, and where you insert your thumb only up to the thumb joint, and not straight. The palm of your hand should still rest lightly on the ball’s surface. This type of grip should enable you to throw the ball stronger and with more power and that should result in higher pin fall.



After the Drilling Happens

Once the holes are drilled into your bowling ball, the bowling technician will make sure that the fit is accurate. In many bowling shops, you can watch your ball being drilled. The traditional bowling ball grip has three holes – a hole for your thumb, a hole for your middle finger, and a hole for your ring finger. This is true whether you are right-handed or left-handed. The technician will adjust the fit by sanding or smoothing out the tops of the holes and/or make the holes larger if needed. As you use your ball, you may notice that you need further adjustments. Here, the technician can add hole inserts that may improve your grip. Of course, if you find that the grip is completely wrong, you will need to get a new ball with a completely new grip.



Learning about the basics of how and why bowling ball holes are drilled a certain way enables you to gain a fuller understanding of the game of ten-pin bowling. How you grip your ball impacts how the ball is delivered to the pins in terms of speed, rotation, lane direction (straight or hook) and, most importantly, pin fall. The traditional grip and even the finger tip grip work for most beginner and intermediate bowlers. Advanced bowlers will usually own more than one type of ball and will use a particular ball depending upon the lane conditions. The grip on each of these bowling balls may also be different, being determined by the type of core in the ball, the ball’s surface material, and how the bowler expects the ball to react down the lane.

Remember that holes drilled into a bowling ball will not change the intended purpose of the ball. A bowling ball designed to travel straight down the alley cannot be transformed into one that excels when thrown as a curve or hook ball. In addition, purchasing a new bowling ball may or may not improve your game. Before you invest in a new ball, work with a coach or have a professional watch your delivery. Game improvement may be directly connected to improving your style of play rather than the purchase of a new ball.