system
Given the following post, respond as if you're commenting on Reddit:
human
[General video games] I just dropped my chest plate and sword off at the blacksmith to be upgraded but what is he actually doing to make them better.
gpt
Having a professional clean, hone and fit your blade could result in a notable change in performance, especially if it's seen a lot of wear and tear, or survived multiple owners; the sword you inherited from an old adventurer or found in a dungeon probably is in dire need of sharpening and tightening of the pommel. In extreme cases, a swordsmith can rework the entire blade geometry for superior performance. Laying in fullers can reduce the overall weight or shift the point of balance without compromising the structure. The bevel of the cutting edge can be altered for superior performance in specific situations (like a deep hollow grind for superior slashing performance on unarmored flesh, or a broader 'axe' grind to penetrate armor and bone without sticking in the target). Retempering can be very useful for ensuring a proper hardness/ductility ratio, and the original temper can wind up f'd if the user abuses the sword (excessive sharpening, sticking it in a campfire, etc). If the fittings are beat up, worked loose, or damaged, swapping them out can result in a *massive* change in handling characteristics (if your sword makes rattling sounds when you swing it around, find a swordsmith *now*). 

For armor, the best resource to return ratio is from upgrading the underlying padding and supplemental materials, as opposed to dinking around with the plate itself. A fresh set of quilted padding (or more exotic/advanced materials, if available) can notably reduce the felt impact of strikes on the plate, and swapping out a pressed-ring chain mesh at the joints for pinned rings (which take longer to make, but have vastly superior performance against piercing weapons) can up your overall chances of avoiding major injury. If there is something inherently defective/damaged about the plate, a good smith can stop any forming cracks or correct any tempering flaws. For "munitions grade" armor (stuff that was mass produced, instead of being fit specifically to you), or worse, stuff you just found on a body, a smith can get it resized to your specific measurements, improving general feel and mobility without compromising protection. 

And that's all mundane changes. Once magic gets involved, the sky is the limits. Runes can be inlaid, elementals can be bound, and all sorts of other shenanigans can be brought into play.