Re: [CAD_CAM_EDM_DRO] Re: are 3/4 shafts good for axis ?

You can mount square bar for the rails(BrightMildSteel), on the X,Y, and
use 'normal' bearings. The weight of the table will keep things in place.
Not good for shipping though, but for home use you can easily build a large
table this way. You only need lateral bearing guides on one rail, and the
more load support bearings you use, the better.

On the Z, which is always more difficult, if you have a short travel as you
say, then round linear will be OK, and to aid things, you can change the
arrangement of the brackets. 'Normally' you have the supports at two ends,
and the two saddles between them. If you have a short travel, you can put a
third support in the middle of the shaft. This will make it very rigid. Or
you can go; support, saddle, support, saddle.

Regards
Roland

On 21 April 2012 00:00, turbulatordude <dave_mucha@...> wrote:

> **
>
>
> My plans are to do wood working. making simple signs, like house numbers.
> ( think large individual letters)
>
> my maximum tool will be a trim router.
>
> I have a CNC mini-mill, so I have no need to attempt to try to do metal.
>
> The cost of 4 BishopWisecarver bearings and needed rails would bump the
> cost of this machine higher than I would like.
>
> I have started looking at taking 2 skate bearings, mounting them on a 45
> and using home ground steel (also on a 45) as the rail. I know this
> presents tremendous hurdles. one is parallel installation of bearings and
> rails.
>
> Since I am only expecting 2-3 inches of Z travel, I hope that round shafts
> would not be a problem. I thought about a 6 inch travel, but that would be
> for foam cutting for lost foam casting. I thing anything would work for
> cutting foam !
>
> Of course, I am re-designing to allow a simple swap out in the future in
> the event I am not satisfied.
>
> I seem to remember a second source for Vee bearings and rails. now it
> seems that only bishop wisecarver offers them. I wonder if there was a
> patient infringement ???
>
> Anyone know where to get hardened Vee rails for a decent price ?
>
> I am not adverse to getting more than I need. I have a second (smaller)
> machine in the future.
>
> Dave
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Jack" <freshwatermodels@...>
> wrote:
> >
> >
> >
> > Dave,
> >
> > Three key questions- What sort of tollerances do you need to hold and
> > what sort of finish do you want? What do you want to make? Axis
> > travel length would also have some impact on the rail.
> >
> > I have a retrofitted mill and a home made 3 axis router. Both aren't
> > like a big rock solid closed loop servo unit but they serve my needs.
> > Much depends on what you are making and the tollerances and finish you
> > need. Another issue is feeds. I can't hog material at 30ipm on my
> > machines but then I don't need to.
> >
> > My shop is geared to make things and I don't build, buy or use a machine
> > with out considering what I am going to make and the cost involved.
> > What one fellow considers a junky machine might serve another fellows
> > needs.
> >
> > Most of what I make on my little mill are tiny metal casting patterns or
> > simple parts which have to be reasonably accurate. The parts I make on
> > my less than precision router are fine if they come out within a few
> > thou or fit together properly. In both cases I sometimes tweek my
> > program to get more accuracy. Often I run a few test parts, measure
> > and then tweek the program and run the parts.
> >
> > Build a machine that fits your budget and needs. If this is mostly
> > just for fun, build cheap and do some learning before you spend the big
> > bucks on building the dream machine.
> >
> > I buy parts off eBay and have had pretty good luck. I especially like
> > Thompson "super slides" which seem to be a good value on the used
> > market. I also use Thompson 5/8" transportation grade ballscrews with
> > reasonable results. Most of my parts are less than 12" long though I
> > often rout them from 24" long planks.
> >
> > Jack
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>


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