Plating gas pipe

[swarfmacdaddy]

Hey all!
just wondering if anyone could answer a question. Im building a jgro style table a bit on the large size, 5ft x 3ft table so i thought i would size up the gas pipe to 1 3/4" gas pipe to reduce flex. my question is,would it be of any advantage to have the pipe chrome plated to make it last longer or are skate bearing races too hard, and would they just trash the chrome? I ask because ive seen mills that have had the ways "hard chromed" advertisied. And is there any difference between "hard chrome" and the chrome that any plating shop would do, or is that just some b.s. to sell mills? How hard are skate bearings and chrome? Thanks!

[Geof]

There is a big difference between hard chroming and decorative chroming. Hard chroming goes on much thicker and the chrome surface is covered with very fine cracks. Too small to see but they act like wicks for lubricants. Hardchroming is ground to size and surface finish after chroming. Decorative chroming is a more or less impervious layer, think corrosion protection on car bumpers, and there is no final finishing. When decorative chroming gets damaged it peels off in strips but hard chroming comes off more in fragments. Hard chroming on surfaces such as the ways of milling machines and lathes or on hydraulic cylinder rods gives a very wear resistant surface but only under conditions where the load is evenly distributed. I doubt that it would be suitable for a high localised load rolling contact. Not because the chrome surface is not hard enough but because the underlying metal deforms elastically allowing the chrome to crack and separate. Think of a hard, brittle painted surface on rubber. Decorative chroming would probably fail for the same reason but it would be more likely to split and peel off.

[swarfmacdaddy]

Thanks Geof,
Guess i just saved money. So would you suggest just leaving the pipe unfinished and replace when worn? I also thought it would prevent rusting but i guess ill just keep them lubed. Thanks!

[Bruggles]

one thing that geoff didn't mention is that hard chrome is generally applied to hardened shaft, the both work togeter as an excellent wear surface that is corrosion resistant. but since the metal under the chrome would be much softer in the case of plating gas pipes, the chrome would just come off where the bearings ride.

[joecnc2006]

what about just sanding them and getting it hardened? any thoughts?

[Bruggles]

Hardening could cause some warping of the shafts, and they won't be pretty when they come back from the harderner. I would recomend to either buy hardened shaft, or use the gas pipe and when it wears replace it or rotate it.

[Geof]

Originally Posted by joe2000che what about just sanding them and getting it hardened? any thoughts?

Will not work. Gas pipe has a very low carbon content and it is carbon that is required for steel to harden. Actually I think that the carbon content is so low it does not even qualify as steel and it is correct to refer to it as iron pipe.

And just in case anyone wonders if it could be case hardened the answer is yes. But there is a catch; you will need to pack the pipes in charcoal in a heat proof container and stick them in an oven at above red heat for many hours then correctly heat treat them.