Graphite vs. Steel: Spine Alignment Differences Worth Knowing

A question we hear often on the bench: does spine alignment even apply to graphite shafts, or is it only a steel-shaft concern? It applies to both, but the manufacturing differences between the two materials change what the spine reading tends to look like and how confidently we can measure it.

Steel: Tighter Tolerances, Clearer Readings

Steel shafts are formed by rolling and drawing flat steel strip into a tapered tube, a process with very tight dimensional tolerances. Even small, sub-millimeter variances in wall thickness around the circumference produce a clear, repeatable spine reading on the deflection board, which is part of why steel shafts have historically been the material most associated with spine testing in club building circles.

Graphite: More Variable, Still Measurable

Graphite shafts are built by wrapping layers of resin-impregnated carbon fiber sheet around a mandrel, a process with more room for layer overlap and fiber orientation to vary around the circumference. This can produce a spine reading that's subtler or, occasionally, less consistent between the tip and butt sections of the same shaft — but it's still measurable, and worth testing rather than skipping because "graphite doesn't really have a spine," which is a myth we hear fairly often.

Subtler is not the same as absent. A subtle spine still deserves to be tested rather than ignored.

Where the Difference Actually Matters

In practice, the material difference shows up most in how many load points we test along the shaft before committing to an orientation. Graphite shafts, especially longer driver and fairway wood shafts, sometimes get an extra deflection board pass near the tip section to confirm the reading holds consistent along the shaft's full length, rather than relying on a single midpoint reading.

The Bottom Line for a Build

Whether your fitting involves a steel iron shaft or a graphite driver shaft, both go through the same deflection board and FLO process on our bench. Material changes how we interpret the data, not whether we collect it.