Heat treatment changes a metal’s hardness and strength—and therefore how (and when) you machine it.
Common treatments
- Annealing: softens for easier machining and forming.
- Quench and temper (hardening): raises hardness and strength; can induce stress and slight distortion.
- Precipitation hardening (e.g., 17-4 PH): ages at moderate heat to high strength.
The smart sequence
For hardenable steels and 17-4 PH, machine in the soft condition, then heat-treat. This avoids cutting very hard material and lets you hold tight tolerances on soft stock, accepting minor post-treatment movement on non-critical faces.
Watch-outs
- Heat treatment can distort thin sections—leave stock and finish-machine critical faces after.
- Hardened parts need coated carbide and rigid setups; expect slower feeds.
FAQ
Can I machine after hardening? Yes, but it is slower and costlier; prefer machining soft then treating.
Does aluminum need heat treatment? Tempers like T6 are standard; most aluminum is machined in final temper. See materials.