Re: Hot rolled router frame: added note - EPOXY

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude
<davemucha@j...>" <davemucha@j...> wrote:

> > > ------------------------------------------------------------------
> -
> > I used hot rolled on my cnc router, drilled all the holes, welded
> > everything up and then used epoxy for my rail base. I set a waxed
> > precision level into the epoxy. This was done first across the ends
> of
> > the two parallels , then down the length of each tube. This gave me
> a
> > +- .001 ready surface for rails. Picts of the manchine are at
> > http://groups.yahoo.com/group/CAD_CAM_EMC/
> >
> > Frank
>
>
> Hi Frank,
>
> didn't see any details on the epoxy. do you have any close up
> photos ?
>
> Also, how strong is the epoxy ? I'm thinking a very heavy table or
> crash might compress sections.
>
> Dave

I didn't take any picts during the build process. I work with epoxies
and polyester resins in my business. Buy a laminating type epoxy, not
a already thickened type. and mix Colloidal Silica ( powdered glass
) better know as Cab-O-Sil. Add enough so the mix resembles a grease
or Vaseline consistency. By thickening the resin with Colloidal
Silica you will end up with bedding mix that will displace easily when
you place the level in it but stay put, not run or sag.

But you asked about epoxies strength. I don't have compression
numbers handy, but they are high enough considering the compression
load is spread across the rail and mount faces and not just localized
at the fastener. Keep in mind you would not be building a thick bed,
no more than 150 or so thousands as Les pointed out, so fracturing is
not a problem. How accurate is this method? Well I ran a dail
indicator down it and watched + - a thousand or two.

I'm not too concerned with high precision , after all I'm running cam
followers on cold rolled steel with a tolerance of .003 in thickness.

I know it's more than you asked.

Found the numbers while writing this -----Compressive yield strength
without silica , 20300 psi ,.. with it 23200 psi. Of course there is
more to it. http://www.matweb.com/search/GetSubcat.asp

Frank