PMMI Mechanical Drives Practice Test

Annealing softens metal by heating it to a suitable temperature and cooling slowly, letting the crystal structure rearrange to reduce hardness and increase ductility. For the ends of a ball screw shaft, this softness makes machining easier and reduces internal stresses from prior forming, helping you cut, drill, and shape with less tool wear and lower risk of distortion. After machining, you can apply the final hardening process if the part needs a higher service hardness. Quenching would harden the metal through rapid cooling, which is the opposite goal for machining. Tempering is used after quenching to tame brittleness and fine-tune hardness, not to soften a non-quenched piece. Normalizing refines grain structure and relieves stresses but doesn’t soften to the same degree as annealing, and can even yield a hardness similar to or greater than annealed metal depending on the alloy.