Re: [CAD_CAM_EDM_DRO] Cold rolled steel, flats or square for use as rails.

Hi Peter,

> 1. If I get the cold rolled rail surface ground for tighter accuracy,
> will a surface ground rail rust more quickly than a non ground rail?
>

No. It won't make any difference.

>
> 2. If I was to use the same cold rolled but this time it was hardened
> and ground. Would it resist the rust more?
>

Hardened may rust slightly less but there won't be much in it. With the
cost of hardening and grinding, you would be better off buying some
proper linear rails. They will be more accurate, more rust resistant and
will last far longer. They would also probably be cheaper.

> 3. How do I stop it from rusting? I can't paint it as it will have
> bearings running across it.
>

Oil or grease is pretty much the only solution. Apart from plating there
isn't much else you can do.

> 5. What if I used stainless steel for a rail. Would it be okay to
> use as an unmachined length, or would it need surface grinding as
> well? Is it more parrallel and as straight as cold rolled steel or is
> it not as straight etc?
>

What are you cutting? If you are machining wood and plastics then an
unmachined stainless rail should be fine. Slot the mounting holes so you
have a bit of adjustment. Tightly stretch a piece of piano wire or mig
welding wire next to the rail but not quite touching it. The wire will
be very straight so you can use it as a reference. Fix the two ends of
the rail then the middle then each quarter and so on. If you spend some
time on it you can get reasonable accuracy. When you assemble you
bearings on the rail you may have to gently relieve any high spots but
again with a bit of care you can get a pretty good result.

Les