Re: [CAD_CAM_EDM_DRO] Linear Slide Components

From: "Lee Wenger" <wenger2k@...>

> 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?

We have a 30% grade road that runs for about 12 miles where I use to
live. A friend thought it would be fun to skateboard down it. He made it
about 1/3 of the way down before the wheels got soft and the bearings came
loose, landing him in the hospital. Other then the fact that they aren't
built to handle heavy loads,and non-stop use, there is no reason not to,
unless accuracy matters. If you aren't going to place heavy loads on it, not
going to use it for more then a little while non-stop and don't need to hold
a tolerance then there is no reason to spend the extra money.

> 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

It's not a cheep hobby.

> I'm not being defensive but rather truly trying to determine the

difference

> between these approaches.

It all depends on what you want to make.

> 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.

It totally depends on how accurate you need to be. A framing square might
well be as good as you need. An option for large home built machines is to
build it with some adjustment in it. Put something large on the table with
the back edge as square as you can. You then cut the back, front, right and
left. Check size to make sure you cut the front/back, left/right even. Then
flip the object on the table over and line up the back edge. When you check
the right or left side it'll be off twice as much as the table is out of
square. Adjust the table until you've taken out half the distance and start
over to make sure it's right.

> 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?

A hammer, a chisel, a file and a micrometer. There isn't a huge amount
you can do with a machine that you can't do by hand. The difference is that
the machine might take 20 min and doing it by hand might take hours, days or
even months. What you are paying for at a shop is mostly their time, but
it's also what they know and the machines they have to do things faster. IE
I have no interest in hand scraping in ways, it's worth the price to send
them out to some one with a big grinder. If it's not worth it to you, then
use what ever tools you do have and do it your self.