Unless you work in a pro shop, bowling ball drill bits are something you might never have thought about. But every set of holes in your bowling ball — the finger holes, the thumb hole, potentially a balance or vent hole — was created with specialized drilling equipment that's quite different from the drill bits you'd find at a hardware store.
Understanding the basics of bowling ball drilling equipment is useful for anyone serious about their equipment, particularly if you're curious about the fitting process, considering equipment for a home pro shop, or just want to understand what the person behind the counter is actually doing when they drill your ball.
What Makes Bowling Ball Drilling Different
Bowling balls are made from urethane, reactive resin, or particle-infused polyester — hard, dense materials that are significantly more challenging to drill than wood or standard metals. The drilling must be extremely precise: a finger hole that's even slightly off in depth or angle can affect your release, cause physical discomfort, or create an inconsistent fit as the ball temperature changes.
Additionally, bowling balls have an internal core — a dense, differently weighted component that determines the ball's motion characteristics. The drill layout (angles and positioning of the holes relative to the core) is a calculated decision that affects how the ball rolls, hooks, and recovers. A skilled pro shop operator is performing a precise layout calculation before drilling, not just making holes wherever convenient.
Types of Bowling Ball Drill Bits
Standard carbide-tipped bits are the most common type for bowling ball drilling. The tips are hardened with carbide inserts that can cut through the dense ball material without dulling quickly. Standard sizes range from approximately 1 inch to 1.5 inches in diameter, covering the range of thumb and finger hole sizes needed for most bowlers.
Stepped drill bits (or combination bits) are designed to create the finger hole in one pass — a wider outer diameter for the entry of the hole and a narrower inner diameter for the depth. These are faster for experienced drillers and create a consistent taper that aids in a clean, predictable release.
Sand core bits (or diamond-tipped bits) are used for particularly hard ball materials or when extreme precision is needed. They cut more slowly than carbide bits but produce cleaner holes with less risk of micro-cracking in the ball surface around the hole edge.
Balance hole bits are used for the additional weight hole (now technically called "balance hole" under USBC regulations, though post-2020 rule changes eliminated the traditional use of this hole to manipulate ball dynamics). When drilled, these are typically smaller-diameter bits.
Pro Shop Drilling Equipment
The drill bits themselves are only one component of the pro shop drilling setup. Professional bowling ball drilling requires:
A dedicated ball drill press: A specialized press designed specifically for bowling balls, with adjustable angle settings and a ball holder/vise that secures the ball during drilling. Consumer-grade drill presses are not suitable — the bit must enter at precise angles that require equipment specifically designed for the task.
An oval hole punch or slug router: For creating oval thumb holes, which some bowlers prefer for comfort and release consistency. The oval shape accommodates the natural shape of the thumb better than a round hole for some hand anatomies.
A measuring system: Calipers, span gauges, and pitch gauges to measure the bowler's hand and calculate the precise span (distance between holes) and pitch (angle of each hole relative to the ball surface) needed for a proper fit.
Drilling Costs and Process
Having a bowling ball drilled by a pro shop typically costs $30 to $75 for a standard three-hole drilling (thumb, middle finger, ring finger). Custom work — oval slugs, inserts, finger tip grips, or complex layouts for competitive players — can run $75 to $150 or more.
The drilling process for a standard ball takes an experienced pro shop operator about 15 to 30 minutes, though the preparation time (measuring the hand, calculating the layout, marking the ball) takes additional time. Rush jobs are typically not a good idea — the precision required means a hurried layout can result in a poorly fitting ball that affects your game.
Note for DIY drillers: Attempting to drill a bowling ball at home with standard drill bits is strongly discouraged. The density of bowling ball material will damage standard bits almost immediately, the precision required is extremely difficult to achieve without dedicated equipment, and an incorrectly drilled ball may be damaged beyond repair. Pro shop drilling costs are low enough that DIY drilling is rarely worth attempting.
Finger Inserts and Grips
Many competitive bowlers use finger inserts (also called fingertip grips) — rubber or urethane inserts that fit into the finger holes and provide a more consistent gripping surface. These require the hole to be drilled slightly larger than the fingertip size to accommodate the insert, which is then glued in place. The pro shop operator will factor insert usage into the drilling layout and hole size calculations.