Most pro bowlers drill their own bowling balls. Pro bowlers tend to own bowling shops or they have drill equipment at their home. All the pro bowlers I have seen, have drilling equipment at their home. By drilling their own bowling balls, their company can just send them new bowling balls and they can drill how they want it. this also saves money so they don’t have to pay someone else to drill the ball for them. Pro bowlers gets new bowling balls all the time so they do need to know how to drill their own bowling balls. Now I am no saying all pro bowlers drill their own bowling balls but most of them do.