Re: [CAD_CAM_EDM_DRO] Re: Hardening rails

Plus what no one is mentioning is that hardening it will have no real effect on the what
he was complaining about(stiffness). Or at least very little.

Garry

To: CAD_CAM_EDM_DRO@yahoogroups.com
From: "caudlet" <info@...>
Date sent: Sat, 22 Nov 2003 19:55:37 -0000
Subject: [CAD_CAM_EDM_DRO] Re: Hardening rails
Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "zxcvbnm12330134"
> <johnatl@m...> wrote:
> > I bought some W-1 Water Hardening Drill Rod to use with my
> > hand-me-down Thompson Super Ball Bushing linear bearings.
> >
> > The write-up said it was usable as-is, which I suppose it is,
> > but it isn't as stiff as I was expecting. Can I heat this with
> > my little propane torch, then quench it in a bucket or with a
> > water hose? I probably won't be able to get the whole thing
> > hot at once. Maybe I could put it in the oven at 500deg?
> >
> > Thanks for any advice!
> >
> > Regards,
> > JJ
>
> There are two processes that have to be used to harden high carbon
> steel. (Case hardening is reserved for low carbon steel and is a
> surface process). First you have to take the entire steel piece up
> over the critical temp (varies with alloys but is 1500 to 1875 deg F).
> Some of the old guys can look at the color at tell you when you get
> to the magic temp. The molecular structure of the steel changes at
> this temp and the crystal structure (grain) realigns. The best way to
> determine critical temp is to heat the steel until a magnet will not
> stick. Once you reach the critical temp it has to be very rapidly
> cooled by plunging (submersing) it into water. The entire "quenching"
> process should not take more than a few seconds. This makes the metal
> very hard and brittle. The next step is to anneal the piece by
> bringing it up to a lower temp and rapidly quinching it again. This
> softens the steel but maintains the toughness. Heating steel then
> letting it cool slowly will completely anneal (maximum softness).
> Taking the metal up anywhere BELOW the critical temp and quenching it
> will not add any hardness.
>
> If you try to do this in sections you will get twisting and warping of
> the rod. There will be soft and hard spots. You have to bring the
> entire piece up to critical temp which means several torches at once.
> At those tempratures scale will form on the surface of the metal
> inless it is in a reduced oxygen environment. This scale will have to
> be removed (normally with grinding).
>
> For precision ways using THK slides, I would suggest you find
> hardened and ground rods, ground to the correct dimension. Heat
> treating steel will cause it to change size and may well be out of
> spec for the bearings. Unless you are familiar with heat treating I
> would not recommend it for making larger critical parts.
>
>
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