making accurate parts with cheap tools Re: Linear Slide Components

Hello,

One of the later books in my "Getting into Motion" cnc series is all
about getting accurate results with inexpensive tools... It will be
out within 3 months.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., Chris L <datac@l...> wrote:
> 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@y...>
> >
> > > 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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