The Temper Guide
Decoding Your Certificate
Most players have never seen this page's worth of terms explained in one place. Here's the plain-language version, whether you built with us or somewhere else.
Rockwell Hardness, Without the Jargon
Press a hardened indenter into a surface under a fixed load, measure how deep it sinks, and that's a Rockwell reading. It says nothing about how heavy a head is or what alloy it's made from — only how the surface resists deformation. Two heads from the same batch can carry different readings if one got tempered slightly differently than the other.
The number lands on the HRC scale, the standard for hardened steel. Softer reads lower, harder reads higher, and forged golf iron heads generally land somewhere between the high teens and mid-twenties depending on the manufacturer's target for that model.
Rough Guardrails
Below roughly 18 HRC, a head tends to feel soft and marks more easily on hard contact. Above roughly 26 HRC, it starts feeling harsh and transmits more shock on off-center hits. Most forged carbon steel heads sit between those two lines — which is exactly why we test the actual head instead of trusting a box.
What Actually Sets the Final Number
Forge Temperature
How hot the blank runs before the die strike. Too cool and steel doesn't flow cleanly; too hot and grain structure suffers, which affects hardening later.
Quench Speed
How fast the head cools after forging, which sets the initial hardness. An uneven quench leaves soft spots the tester picks up immediately.
Temper Soak
A controlled reheat that relieves brittleness from the quench and settles the final hardness, held for a set time rather than eyeballed.
Hardness Isn't Head Weight
Weight is mass, measured in grams. Hardness is surface resistance, measured with the tester. A head can weigh exactly to spec and still read soft or hard depending on how it was heat-treated. Both numbers matter and answer completely different questions — a spec sheet listing only one is missing half the picture.
Why Otherwise-Identical Heads Drift
Furnace hot spots, inconsistent soak timing, and a quench bath that crept up in temperature over a shift can all shift final hardness by a point or two, invisibly. The catalog describes a target; the certificate describes what actually happened to the head in your hands.
Everything Else on the Sheet
| Term | Meaning |
|---|---|
| HRC | Rockwell C scale — the standard hardness measurement for hardened steel. |
| Quench | Rapid cooling right after forging, sets initial hardness ahead of tempering. |
| Temper | A second, gentler reheat that relieves brittleness and locks in the final hardness. |
| Grain Structure | The internal crystal arrangement of the steel, which shapes how it responds to heat treatment. |
| Case Hardening | Hardening only a component's outer surface — different from through-hardening a full head. |
| Indenter | The diamond or steel point pressed into the surface to produce a reading. |
| Heat-Affected Zone | Metal near a weld, bend, or grind that gets reheated by the process itself — always worth a recheck. |
See These Numbers on Your Own Clubs
Bring in whatever you play and we'll walk through every term on this page directly off the tester.