I think it all depends on what you are trying to do, for a lot of hobby machines they don't see that much work and if a rail is really cheap and it wears then you replace it, same with nuts etc. It is a different way of thinking about it expensize linear rail lifetimes are rated in 10's of Km but half the time we don't need that. Main thing I suppose is to have something that is flat/straight enough.
If you look for example at CNC plasma cutter kits they use cold rolled bar as the rail, why? Because it the accuracy matches the cutting process and when they wear you replace them for peanuts (not with peanuts, that doesn't work).
So in this case if the blocks were delrin the need for hardening would seem to be less and again they could be replaced if needs be.
Why not make a test pair for the z-axis |