Re: [CAD_CAM_EDM_DRO] Linear Slide Components

Lee: Let's see if I can copy some of your question-text, and insert my
answers — which will probably be no more than "MY opinion", as I am not a
wizend old highly-trained machinist, but a home-brewer with 30+ years'
experience:

> Why, why is it that a V-wheel on angle iron or skateboard wheels against a
> hard flat edge is such a horrible idea?<<

You are not a "machinist", are you? Do you perceive the difference between
"fine cabinetwork" and "carpentry"? A skateboard on hot-rolled angle-iron is
like lumber-mill-sawn fence-posts and barn- building vs. Chipendale
cabinetwork. Nuff said?

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.<<

Don't perceive your point, here. How does "total science project" enter into
this discussion? I built a 5'x12' with Thomson linear bearings, 1.5" dia.
preloaded (double-nut) ball-screws, and "job-shop made" carriage parts to
hold the router (A 3.5 hp Perske 400 Hz machine, with motor-generator "freq.
converter"), and my total cost was $40,000. You can't DO this kinda thing
with skateboards and apple-crate salvage!

>
> I'm not being defensive but rather truly trying to determine the difference
> between these approaches.<<

One approach is just expensive, but right. The other approach is DON'T!

>
> 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.<<

If you build it of milled hardwood and Baltic Birch plywood, and work with
machinist-discipline, not "carpenter/bridge-builder discipline", a
framing-square should do just fine! If you framing members are SO poorly
milled that the irregularity over an 8' or 10' length will spoil use of a
framing-square, it is TOO crude! Simple as that! But, you could still use
the "diagonal-match" method for an "overall square": Measure the
diagonal-distance betwee inside-corners of your frame, NW-SE, and SW-NE. If
equal, the "box" is square (rectangular with 90° corners). OLD trick!

>
> 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?<<

Here's the story on that: If it's worth DOING, either "bite the bullet" and
buy yourself the needed machinery, and DO it. Or, if that would be too much
of a seldom-used investment, then, the RIGHT way is the "jobshop route"
(Which you call here "commercial machine shop"). What, are you a fine
cabinetmaker, but can handle a hack-saw and drill-press? Then, build the
"structure" of hardwood, using glue and screws and proper joinery, and METAL
for such as bearings, rails, etc. Thomson, etc! That's why that stuff COSTS
so much! It is PRECISION, proper product, not "cobbled in a barn with a
sledge and a charcoal furnace with hand-bellows!

Lotsa luck! Jan Rowland, old troll who's been there, done that.




[Non-text portions of this message have been removed]