How do you install bowling ball inserts?

Answer 1

For plastic, urethane or rubber inserts, a hole is drilled the size of the outer diameter of the insert to be used. Care must be taken to factor how the span of the inserts are placed with where the holes are placed. After drilling has been done, the inserts are glued in.

While thumb inserts can be replaceable, it's more common to drill a large hole where the thumb goes and a solid thumb insert is glued in the hole. The thumb hole is then drilled into the solid insert.