Summarize the following:
Place the ball into a tight clamp to ensure that it does not move during drilling. If the ball moves during drilling, the holes may come out uneven, making the ball uncomfortable to use or difficult to control. With an erasable marker or piece of chalk, mark the hole configuration, placing a mark at the center of the spot you plan to drill each hole. Use your span measurement to assure the holes will be properly placed. When bowling balls are molded, they are suspended by a small rod that, when removed, leaves a hole that must be filled in. This is called the "pin." You should avoid drilling through the pin, as this may void your warranty and negatively affect the ball's performance. Make sure your nearest hole is at least an inch away from the pin. The pin should be easy to locate. It is usually a different color than the rest of the ball. For advanced ball drillers, the pin is used to determine properties of the bowling ball's core that can be used to determine the ideal location on the ball to drill finger holes, depending on the qualities you want the ball to have. This will vary from one model of ball to the next, so if you want to try this, you should consult the instructions that came with your ball. It's a good idea to double check your marks against your span measurements before drilling. Once the holes are drilled, they are permanent. Determine the correctly sized drill bits to create comfortable holes for your thumb and fingers. You can determine this easily if you used a sizing ball to get your hand measurements, as these balls also provide information on your thumb and finger widths. If you did not have the benefit of a sizing ball, a good way to determine this is to experiment with different bits, drilling holes of different sizes into a block of wood and then determining which ones most comfortably fits your thumb and fingers. Prepare your bowling ball drill with the proper bit for your thumb width. It is strongly recommended that you use a bowling ball drill. Attempting this with an ordinary drill may damage your ball. Drill the hole slowly at your desired angle, checking the depth often so as not to drill too deep. Swap out the drill bit and drill the two finger holes. As with the thumb hole, check the depths often to avoid drilling too deep. Replace the drill bit with a sanding attachment and sand the interior of the holes until they are smooth and our fingers slide in and out easily and comfortably.
Clamp the ball in place. Mark the ball. Select your bits. Insert the first bit. Drill your thumb hole. Switch bits and drill the finger holes. Sand the holes.