Re: [CAD_CAM_EDM_DRO] Linear Slide Components

Ray, others..... you all bring out good points.

Ray in particular brings out that interestingly enough, One can build a pretty nice machine without too many fancy tools, just plain old ingenuity. Think back the the good old days when you would
scribe a line on a chunk of aluminum and then cut it out with a bandsaw. Worked back then ! Instead of sanding the bandsaw marks out, Edges can be made smooth and straight by clamping a straight edge
on the part and running your conventional handheld wood router along the edge.

If you need perpendicular holes drilled... Well, get one of those little devices with the adjustable base that can hold your 3/8" drill upright and make relatively straight plunges.

"Cap Screw Countersinks" ? No need for a whole set of those. What do you think Black and Decker Bullet Bits were made for ?? Just be sure you drill the countersink first, then the thru hole.

Get this, One fellow who purchased my CNC Router plans reported that he did not have the funding to send all of the critical parts out for machining. To make the pockets in aluminum to hold Lead
screw bearings and the like, He says he chucked a conventional wood paddle bit in his lathe, "ground" the edges to match the diameter he needed to make a pocket, then with his drill press in low gear
and lots of WD-40, Plunged the necessary Pockets. Now thats proof it can be done for less ! I'd bet if he positioned the starter hole correctly with his trusty scribe, His machine has the same
accuracy as one with pockets made on a Mill.

When doing a "seat of the pants" project, I think one should spend as much time planning as possible analyzing just how you can make it accurate enough for your needs without the "right" stuff.

One very important hint in this regard is to >design< accuracy into your machine, by RELYING on the thickness and dimensioning of the"off the shelf" and readily available Cast and Ground (machined)
materials. If you can do that, Then, you already know what tolerances you will end up with, based on the vendors specifications of the raw stock. If you are understanding what I just said, you will
realize that in many cases. the "profile" of a particular part and its "finish" likely won't matter ! You could whack it out with an Axe if you do not care what it looks like, yet it >could< still be
very accurate.

Back to Lee's question about the "real" linear stuff...... I understand your Pain. The stuff is just plain overpriced because in most cases, it is sold to companies who clearly have lots of money to
spend. I've wondered for quite a while in a world of Cheap import "knock-offs" where the knock-off Linear Rail is.. I guess there is none.

The "Real" stuff might determine how many machines you end up building. I get the feeling that the reason that some are on their 3rd and 4th machine for their own use might just be that they

>>thought<< they could "get by" with Rollerskates and what-nots. Sure, Could be that some are just making a bigger machine. Thats different. But, The fact of the matter is, one finds out real quick

that you can't hold close enough tolerance for the projects that you will >without doubt< end up "trying to do". Trust me, even with simple signmaking, I'd be pretty crabby with anything that had more
than .002 repeatability. Just be forced to stop somewhere in a job once and then come back to the same spot. You'll quickly see just why you should not have used anything but the real stuff.
Inaccuracies like this show up a whole lot if you do any Engraving work.

I'd rather go thru the work once and end up with something I know will be good enough. Spend the money for the real stuff. It's worth it. Be happy E-bay makes some of these items available at prices
the rest of us can afford.

And, like Ray, I too think one can make a very accurate machine without necessarily spending big big bucks. Just think things out first, and keep things in perspective for what you NEED the machine to
do, and in the back of your mind, ask yourself how many machines you want to make to get there.

Chris L


Raymond Heckert wrote:

> I believe, if one were determined, he (she?) could make a very decent
> CNC-ready router or plasma cutting table with just a good drill press, and
> a bandsaw, (okay, throw in a good welder, too) using as many
> 'off-the-shelf' items as possible from McMaster-Carr, MSC, KBC, SPI, and
> the likes. Oh, and a good deal of ingenuity! Just how accurate do you need
> to be? With a 3ft x 4ft table, if you could measure to within 1/16" at the
> 3 ft length, you would still be within 3 minutes of arc, of being
> "square"... a 1/32" error would put you within 1.5 minutes! (The 4ft & 5 ft
> legs would yield even smaller errors, hence the 3ft choice).
>
> RayHex
> ----------
> > From: Lee Wenger <wenger2k@...>
>
> > First of all my interest is predominantly for a CNC router as
> > opposed to a mill and or plasma cutter. Although I think my questions
> would
> > certainly apply to the creation of a plasma table.
> >
> > One of the major elements is obviously the linear slide components and to
> be
> > perfectly honest I don't understand why the need (in other words, the
> > quantifiable difference) to use commercial quality components that
> increase
> > the cost so dramatically. People regularly bash any use of anything
> other
> > than commercial grade linear slide components? Why, why is it that a
> > V-wheel on angle iron or skateboard wheels against a hard flat edge is
> such
> > a horrible idea? From what I've seen, as soon as you use any
> commercially
> > available linear components the cost of those components alone is well in
> > excess of $1000 for a 4x8. Of course there is the eBay option but
> > personally, ideally, I'd like to do something that is reproducible as
> > opposed to a total science project.
> >
> > I'm not being defensive but rather truly trying to determine the
> difference
> > between these approaches.
> >
> > Another question I have is how does one go about squaring a large table.
> I
> > certainly know how to do traditional construction type of squaring and
> what
> > a 3-4-5 triangle is and all that but how on earth do you measure these
> > things to sufficient accuracy on such a large scale. I'm assuming my
> > framing square will be completely useless as it would only be suitable
> for
> > initial setting but I would need a far more accurate way to finalize my
> > squaring.
> >
> > Last question, I don't own a mill and will need to make some parts for my
> > machine. Do you all have suggestions as to lower cost ways to produce
> some
> > of the machined parts I need made outside of the traditional commercial
> > machine shop?
> >
> > Thanks in advance for all of your help.
> >
> > Lee Wenger
> >
> >
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