Deciding exactly how to drill holes in a bowling ball is the first real step toward taking your game seriously. If you've been using house balls for years, you're probably used to that awkward feeling of trying to find a ball that doesn't make your thumb feel like it's rattling around in a sewer pipe or, worse, getting stuck and nearly taking you down the lane with it. Getting your own ball is a game-changer, but it's only half the battle. The way those holes are mapped out and cut into the coverstock determines everything from your comfort level to how much hook you can actually generate.
Why the Custom Fit Actually Matters
Most people think you just poke three holes in a sphere and call it a day, but it's way more nuanced than that. Your hand is unique. The length of your palm, the thickness of your knuckles, and even how much your skin stretches all play a role in how a ball should be drilled. When you have a ball that fits like a glove, you don't have to "squeeze" it to keep it from falling off your hand during the backswing.
Squeezing is the enemy of a good bowling stroke. It creates tension in your forearm, which leads to a pulled shot and a lack of consistency. When the holes are drilled correctly for your specific hand, the ball stays on your hand through centrifugal force and a light, relaxed grip. This allows for a much smoother release and, ultimately, more pins falling over.
The Difference Between Conventional and Fingertip Grips
When you sit down to plan how to drill holes in a bowling ball, the first big question is: conventional or fingertip?
Conventional drilling is what you see on every house ball at the local center. Your middle and ring fingers go into the ball up to the second joint. It's very secure and great for beginners or people who just want to throw the ball straight. It gives you a lot of control, but it makes it pretty difficult to put a lot of "revs" or rotation on the ball.
Fingertip drilling, on the other hand, is what almost every competitive bowler uses. In this setup, your fingers only go in up to the first joint. This creates a longer "span" (the distance between your thumb and finger holes). It feels a bit weird at first, like the ball might fall off, but it allows your fingers to stay in the ball a fraction of a second longer during the release. That extra bit of leverage is what creates that powerful hook that snaps into the pocket.
Taking Measurements: It's More Than Just Finger Size
A professional will use a tool called a "bowling ball pitch gauge" and a "span ruler" to figure out your hand's geometry. They aren't just looking at how wide your fingers are. They're looking at the span—the distance from the base of your thumb to the creases of your fingers.
Then there's the "pitch." This is the angle at which the holes are drilled into the ball. Holes aren't always drilled straight toward the center of the ball. Sometimes they're angled forward, backward, or to the side.
For example, if you have very flexible thumbs, you might need "reverse pitch" to help the ball come off your hand cleanly. If your fingers are stiff, the driller might angle the holes toward the palm to help you hold on. It's a delicate balance of physics and anatomy.
The Actual Process of Drilling the Ball
Once the measurements are mapped out with a grease pencil on the surface of the ball, it's time for the drill press. This isn't your average garage drill; it's a high-precision machine with a specialized jig that holds the ball perfectly still.
The driller starts with the thumb hole, usually the largest bit. They have to be incredibly careful with the depth. If they go too deep, it doesn't hurt the performance much, but if it's too shallow, your thumb won't sit right. After the thumb, they move on to the finger holes.
During this process, the driller is also thinking about the "core" or the weight block inside the ball. Modern bowling balls have complex shapes inside them that dictate how the ball wobbles and rolls. Where you choose to drill the holes in relation to the "pin" (a small colored dot on the surface) will actually change how the ball reacts on the lane. You can drill a ball to be "aggressive" or "smooth" just by shifting the hole locations a few centimeters.
What About Inserts and Slugs?
If you look at a pro's ball, you'll notice the holes aren't just raw plastic. They usually have rubber or urethane pieces inside them.
Finger inserts (those squishy colorful tubes) are great because they provide a consistent feel and better "tackiness" for your fingertips. They come in different shapes—some are smooth, and some have a "power lift" ridge that helps you get even more rotation.
Thumb slugs are solid cylinders of urethane that are installed into the ball first, and then the thumb hole is drilled into the slug. This is done because the inner material of a bowling ball can be a bit grainy or inconsistent. A slug ensures the inside of the thumb hole is perfectly smooth, which is vital for a clean release. There are even "interchangeable thumb" systems now where you can pop your thumb sleeve out of one ball and click it into another, so every ball you own feels exactly the same.
Why You Should Probably Visit a Pro Shop
I know it's tempting to look for a DIY way to drill holes in a bowling ball, especially if you have a drill press in the shed. But honestly? Don't do it. Bowling balls are expensive, and even a tiny mistake in the pitch or span can make a $200 ball feel like a $10 paperweight.
A Pro Shop Operator (PSO) does more than just drill; they observe. A good one will ask you to throw a few frames before they ever touch a drill bit. They want to see your "Positive Axis Point" (PAP), which is the point on the ball that stays stationary as the ball starts to rotate. Knowing your PAP is the only way to drill the ball so that the internal weight block works for your specific throwing style.
Maintaining Your Fit Over Time
Your hand changes. If you lose weight, gain weight, or even if the weather changes, your fingers will swell or shrink. This is why many bowlers use "bowler's tape." You can stick small strips of textured tape inside the thumb hole to tighten it up on cold days or peel them out when it's humid and your hands are swollen.
If you find that you're constantly getting blisters or calluses in weird spots, it's a sign that your drill pattern is off. You don't necessarily need a new ball, though. A pro shop can "plug" your existing holes with a special resin that hardens overnight and then redrill them in a better position.
Wrapping It Up
At the end of the day, how you drill holes in a bowling ball is the most personal part of the sport. It's the literal connection between your body and the equipment. Taking the time to get a custom fit—and understanding the logic behind the span, pitch, and grip style—will do more for your score than any high-tech coverstock ever could. Once you have a ball that actually fits, you can stop worrying about holding onto the ball and start focusing on hitting your target. And that's when the game really starts getting fun.