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What is spine alignment in a golf shaft? 

The spine aligning we do at Value Golf (also sometimes called “spining” - or [inaccurately] “spline” aligning) is a club building procedure to locate a golf shaft's most stable bending plane, usually called the “neutral bending plane” or “natural bending plane”, often abbreviated as NBP. And  after locating that stable plane, installing the shaft in a specific orientation relative to the target line for the highest performance. (note that there is another debate I won’t get into here about whether to align the hard spine toward the target or the neutral or natural bend plane toward the target. I do not agree with aligning the hard spine toward the target is the way to go and I think you will understand why if you read on)

Why would aligning a golf shaft a certain way even be necessary? For one, no golf shaft is perfectly round or perfectly uniform in stiffness. Every steel golf shaft for example has a welded seam, and graphite shafts have layers