The basis of spining or PUREing is finding the neutral plane of the golf shaft so any unnecessary QuarterInch1.JPG (79275 bytes)deflection is minimized. Spining is the generic catchall term for this process: from simply clamping a shaft in a vise to see where it wobbles, to PUREing, which employs specific trademarked proprietary software and equipment.
Always keep in mind companies that tout spining or PUREing have an expensive apparatus to pay for, and they'll insist you must have it done to achieve maximum performance of your equipment. The reality is different companies will proffer different test results, all proclaiming theirs to be correct. If you examine their findings you'll see they can't even agree where the shaft should be aligned in the club head. 12:00? 3:00? 9:00? In fact, using the most popular shafts available, we doubt any of these companies would be confident to challenge a player to a $100 payoff if they could positively tell whether their shaft has been spined or not.