Home > Sports > List > Tenpin > Equipment > Balls > Drilling

Ball drilling

Ball drilling requires a specific machine, such as this one pictured on the left, experience and specific skills. Most bowling centers or stores provide drilling services or can direct you to someone who can do it for you.

How do they determine where to drill my finger holes?

This is an example of the type of sheet used by a ball driller. It has on it the range of information required for the ball driller to determine where to place the holes.

How many holes are allowed in a bowling ball?

The rules of tenpin bowling allow for a total of 12 holes in each ball.

You are allowed one for each finger and thumb for gripping purposes.
You are all allowed one small vent hole for each of the fingers and thumb holes, to prevent popping at the release point.
One hole for balance purposes, not to exceed 1 1/4" in diameter, to bring a ball into static weight tolerances.
The last is a "mill" hole for inspection purposes, not to exceed 5/8" in diameter and 1/8" in depth. This is used to check the hardness of the cover stock just below the actual surface of the ball. This is the hole seen on equipment used by members of the PWPA and PBA National Tours just above the finger holes.