- 1. Disclaimer
- 2. Conventional balance hole wisdom
- 3. Balance hole examples
- 3.1. Symmetrical ball, 50 x 5.5″ x 65 (layout A), no balance hole
- 3.2. Symmetrical ball, 50 x 5.5″ x 65 (layout A), flare-decreasing balance hole
- 3.3. Symmetrical ball, 50 x 5.5″ x 65 (layout A), flare-increasing balance hole
- 3.4. Symmetrical ball, 60 x 4″ x 30 (layout B), no balance hole
- 3.5. Symmetrical ball, 60 x 4″ x 30 (layout B), flare-decreasing balance hole
- 3.6. Symmetrical ball, 60 x 4″ x 30 (layout B), flare-increasing balance hole
- 4. Not all identical balance holes are created equal!
- 5. Suggested way to think about balance holes
- 6. Conclusions
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Let’s start with a quick question: Have you ever heard a fellow bowler say any of the following statements?
- “I just don’t like balls with balance holes. They don’t roll well for me.”
- “I’m going to have a weight hole put in the side so my ball will hook more.”
- “You only need a balance hole if your ball has too much side weight.”
These types of statements range from slightly misinformed to 100% wrong. Whenever I hear stuff like this, I know I’m talking to someone who really doesn’t understand how balance holes work. That’s OK, of course; no one person can possibly know everything about all topics. That’s why we’re here – reading, learning, and trying to become the best bowlers, ball drillers, and coaches we can be.
This article will attempt to provide a “crash course” in everything a bowler, pro shop operator, or coach needs to know about balance holes. I’ll start by discussing the current conventional thinking on balance holes, to provide the appropriate background for the remainder of the article. Next, I’ll show some “before and after” examples of what adding a balance hole can do to a ball’s motion. And, finally, I’ll give you my general thoughts on how you should think about balance holes so that you can more often understand what effect a given hole will have BEFORE you waste your time and money drilling it.
I like to tell it like it is. So, before we get too far, I think it’s helpful to set some reasonable expectations. In general, balance holes are nothing more than a tool for fine-tuning ball motion. Unfortunately, you probably aren’t going to learn anything in this article that will add 20 pins to your average, give you 10 boards more hook, or make you carry the 10 pin 100% of the time.
However, learning about balance holes has very real and tangible benefits. A solid understanding of balance holes can help you get more out of your current arsenal. Balance hole knowledge can help you make better layout choices. And, proper use of balance holes can help you match up and have better ball motion a bit more often than you might otherwise. These are all good and valuable things, of course, but just keep in mind that a well-placed balance hole is never going to be a substitute for proper execution.
In the end, I hope you’ll walk away from this with not only a better understanding of balance holes themselves, but also with an improved understanding of layouts, ball dynamics, and ball motion in general. Let’s get started!
Conventional balance hole wisdom
In the beginning, balance holes (more commonly called “weight holes” back in those times) were used almost exclusively for the purpose of getting a drilled ball back to within the legal limits for static imbalance. Most commonly, a weight hole would be used to take a ball with too much side weight and get it back down to less than 1 ounce of side, which was and still is the maximum amount of side weight imbalance allowed by the then-ABC and the current USBC.
Sometime in the fairly recent past, ball drilling experts began to realize that a weight hole could also be used to manipulate a ball’s RGs and differentials. This opened up a world of possibilities for what could be done with a balance hole. The focus was shifted, and the purpose of a balance hole was no longer primarily to make a ball’s static weights legal. Balance holes began being used to significantly alter ball motion.
The most popular balance hole system or methodology in use today is the Gradient Line Balance Hole system, developed originally by Mo Pinel and his collaborators during his years owning and operating MoRich Enterprises. In short, this system defines four standard balance hole positions (P1, P2, P3, and P4) that can be used to alter the motion of the ball:
- P1 holes slightly weaken the ball’s motion by reducing its differentials and cutting down on its track flare.
- P2 holes have almost no effect.
- P3 holes moderately strengthen the ball’s motion by moderately increasing its differentials and moderately increasing its track flare.
- P4 holes significantly strengthen the ball’s motion by significantly increasing its differentials and significantly increasing its track flare.
Of course, prior to the development of the Gradient Line system, many of the more highly-skilled ball drillers already understood the basics of balance holes. They knew, for example, roughly where to put the extra hole to strengthen the reaction, and roughly where to put it to weaken the reaction. The Gradient Line system just gave a bit more structure to the process of picking a balance hole position. Instead of having an unlimited number of possible balance hole locations to pick from, ball drillers now had four standard positions, and each of them produced a certain outcome. All in all, the Gradient Line Balance Hole system was a big step forward, as it gave us a common vocabulary and framework from which to work. That’s a heck of a lot better than everything that came before it, and I would strongly recommend that all bowlers and ball drillers familiarize themselves with the basics of this system.
Balance hole examples
I’d like to walk through a few hypothetical scenarios to illustrate how various balance holes will affect a bowling ball’s on-lane motion.
As some of you know, I’ve spent an unreasonably large number of hours over the last five or six years studying the physics of bowling ball motion, culminating in the development of a software tool called Powerhouse Blueprint. In short, this piece of software is a bowling ball motion simulator. It implements a very complex set of equations that govern the motion of a drilled bowling ball, allowing for accurate studies such as this one that isolate the causes and effects of ball motion. It’s my tool of choice for demonstrating ball motion-related concepts, though I will admit to being a bit biased as one of its creators. All of the images and simulation data shown below were generated using a not-yet-released development version of Blueprint.
These examples all use a hypothetical symmetrical bowling ball with an RG of 2.54″ and a total differential of 0.041″. It will be “thrown” by a hypothetical bowler who has a ball speed of 18 mph, a rev rate of 300 RPM, 50 degrees of axis rotation, 10 degrees of tilt, and a positive axis point (PAP) of 4.5″ over and 0.5″ up. All of the simulations shown use the exact same oil pattern and all deliveries are thrown along the exact same target line. In other words, the only things that are changing from one example to the next are the layouts and balance holes.
Symmetrical ball, 50 x 5.5″ x 65 (layout A), no balance hole
In this first example, let’s start by drilling our ball with a fairly weak pin-down layout with Dual Angle parameters of 50 x 5.5″ x 65 (which we’ll refer to throughout as “layout A”). This ends up being a fairly low-flaring configuration, having a total track flare of about 2.7 inches.
Below is a short video showing how this ball reacts on-lane. Note that in this video and all the others that follow, the same exact shot is shown three times in a row. Also, note that these videos are probably best viewed in full-screen mode, with the quality set to full 1080p HD mode.
As shown, this ball manages to get back up to the pocket, but it hits a bit light. Specifically, it gets up to board 16.15 at 60 feet, with an entry angle of 5.3 degrees.
Symmetrical ball, 50 x 5.5″ x 65 (layout A), flare-decreasing balance hole
Now, let’s add a flare-decreasing balance hole to this ball. Specifically, this hole is 1 inch in diameter and 3 inches in depth, located slightly above the bowler’s PAP on the vertical axis line. In terms of the Gradient Line Balance Hole system, this hole is approximately in the P1 position.
As the picture above shows, adding this balance hole does in fact cut down on the ball’s overall track flare, taking it from 2.7 inches of total flare before the addition of the hole to about 1.6 inches of total flare after. Let’s take a look at what that translates to in terms of ball motion:
Thanks primarily to the flare reduction, this ball hooks about two boards less than it did before adding the hole. It doesn’t quite make it back to the pocket and ends up on board 14.24 at 60 feet, with a lower entry angle of 4.5 degrees.
Symmetrical ball, 50 x 5.5″ x 65 (layout A), flare-increasing balance hole
Next, let’s look at how a flare-increasing hole affects this ball. This time, our balance hole is 1.125 inches in diameter and 3 inches in depth, with a location of about 2 inches to the right ...