Guideways are hardened by which hardening method?

There are several ways of hardening the ways of a machine (like a lathe). Let's jump around a bit and see what's shakin' here. You are probably familiar with what is called work hardening. If you have a coat hanger you wish to cut, but have no cutters, you can bend it back and forth to change the metallic crystal structure in a specific area. Bending it makes the crystal structure smaller, and smaller crystals are harder than large ones. The flexing of the mild steel will harden it, and then it will "flex less" and finally break there. When we "work" iron (which is a material of choice for machine housings), we harden it. Shot peening, using small shot blasted on metal parts (like the connecting rods of pistons which we "upgrade" in automotive machine shops) does the same thing on the surface of the rods. It work hardens them. If we can "work" metal, we can harden it. So how do we "beat on" a lathe bed? Glad you asked. There is an industrial process that is widely used to heat, weld or otherwise modify materials called ultrasonics. Imagine a speaker, but small, very high powered and operating at a really, really high frequency (above audible sound - ultrasound). If we can "beat on" stuff with the mechanical energy created by this device, we can ultrasonically modify it. We can harden metal with it. And by ultrasonically treating the ways of a lathe bed, we can beat the heck out of the local crystal structures, reduce the size of the crystals themselves, and thereby harden the material (after which we machine it true). Ultrasonic hardening. Done deal.