[austinblake92]

Im planning on building a 5 ft by 9 ft cnc router, i would like to use 20mm hardened steel for the x y and z but the prices for that much hardened steel is thru the roof. so i managed to find a local steel supplier with untreated steel rods that are 20mm and are 10 ft long. I know its not hardened like your supposed to use but i plan on welding a piece of angle iron the entire length of the bottom of the 20mm steel shaft. and i ll use the open bottom linear shaft bearings. Im just concerned that since the steel shaft is not chrome plated it will rust. so do you guys no of any solution to keep the steel from rusting and will be strong enough to hold up to the linear bearings constant movement. Im thinking i may be able to just wd40 it every so often, or keep it well oiled. any help would be greatly appreciated thanks

[Dylwad]

Bad ideas all around, you will end up with warped, rusty and grooved rails, and the bearings will most likely not be a precise fit to the rails.

I would try to save money other ways.

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[Dylwad]

And if you do end up going along with your plan, get a bottle of eezox gun cleaner/lube/protectant. It goes on wet, dries completely and leaves a very thin film behind that prevents rust and adds some lubrication. Wd40 would need to be applied every few days. Eezox maybe twice a year.

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[ger21]

+1. Non hardened shafts aren't accurate, and aren't hard enough to use with linear bearings. They'll have grooves worn in them very quickly.

[widgitmaster]

Plain old bearings on three sides of a flat bar would work!
But soft steel is no match for the extreem surface force of a 3mm diam rolling ball bearing!
It would burnish a groove in the steel in days of use!

[louieatienza]

Not only will you have problems with the non-hardened surface, you have to make sure that the 20mm steel rods you buy are precision ground drill rod or the like, and then you'd have to get them hardened before you use them. The tolerances on rolled rods are not as good, and it may cause binding/looseness. There are companies like Glacern Tool Works that sell linear rails cheaply enough... Water-hardening drill rods are supposedly "harder" than oil hardening because they have more carbon, but still, I would check out other readily made alternatives.