Bowling Ball Drilling: Span, Pitch and Finger Fit Explained

Bowling ball drilling decides how the ball sits in your hand: how far apart the holes are, how large they are and at which angle they are drilled. A good fit lets you hold the ball with relaxed grip pressure and release it cleanly. This guide explains span, pitch, hole size, grip styles and inserts, and what to expect at the pro shop.

Why fit comes first

A personal ball should be drilled for your hand, not copied from another bowler or taken from a generic chart. A qualified driller looks at finger and thumb size, span, flexibility, grip style and the way you release the ball.

Do not drill or enlarge holes yourself. Drilling changes the ball permanently, and a wrong span, pitch or hole size may mean plugging and redrilling. The IBPSIA (International Bowling Pro Shop and Instructors Association) offers training and certification for pro shop technicians.

Conventional or fingertip grip

Conventional grip

The middle and ring fingers go into the ball up to the second knuckle, with a shorter span. The grip feels secure and is familiar from house balls.

Fingertip grip

The fingers go in only up to the first knuckle, with a longer span. At release the thumb leaves the ball first, and the fingers can lift and rotate it more, which supports more revs and hook.

Neither grip is tied to a skill level. Choose together with your driller or coach, based on comfort, flexibility and the release you are learning. Switching from conventional to fingertip is a new fitting, not just larger holes. More on hook and straight styles: hook vs straight ball.

Span, pitch and hole size

• Span: the distance between the thumb hole and the finger holes, measured from their gripping edges. It should let your hand lie naturally on the ball, neither stretched nor cramped.
• Pitch: the angle at which each hole is drilled, measured against a line to the center of the ball. Zero pitch points straight at the center; forward pitch angles towards it, reverse pitch away from it. The driller chooses the pitch for each hole individually, depending on your span and flexibility.
• Hole size and shape: fingers and thumb should go in to the intended depth and come out without catching. Snug, but without having to squeeze.

These measurements affect each other. A problem that seems to come from one hole may be caused by span, pitch or grip pressure, so ask for a complete fit check rather than a single change.

Finger inserts and interchangeable thumbs

Finger inserts (grips) change the diameter, texture and feel of the finger holes. A thumb slug gives the driller a uniform material to shape the thumb hole. Both have to match your hand; replace them when they are worn or no longer fit.

Interchangeable thumb systems use a removable thumb insert that locks into compatible balls. This gives you the same thumb feel across several balls and lets you switch to a slightly different size if your thumb swells or shrinks. Several systems are on the USBC list of approved removable devices. Have them installed and fitted by a driller.

When to have the fit checked

• You have to squeeze the ball to hold it.
• The thumb or fingers stick, rub or leave pressure points.
• Your hand has changed, for example through growth, swelling or injury.
• You change your grip or release.
• You bought a used ball: someone else's holes are not your fit. A pro shop decides whether plugging and redrilling makes sense.

What happens at the pro shop

1. Conversation: grip, release, goals, changes to your hand and any discomfort.
2. Measurement: each finger, the thumb, span and flexibility.
3. Choice: conventional or fingertip, inserts, thumb slug or interchangeable thumb.
4. Drilling: pitches and depths are set, edges bevelled, inserts fitted.
5. Fit check: hold the ball and, where possible, throw a few shots. Mention any sticking, rubbing or pressure before you leave.

Ask for a copy of your final measurements. It helps with your next ball, but it is no substitute for a new check: hands and releases change.

Pain is a stop signal

If pain starts while bowling, stop. A pro shop can check your equipment but cannot assess an injury. If symptoms persist or get worse, see a doctor or physiotherapist.

Before you drill

Choose a weight you can control with our guide to bowling ball weight, and compare materials in bowling ball coverstock types explained. The whole process in order is covered in how to choose your first bowling ball. New to the sport? Start with the beginner's guide to bowling.