Re: [DIY-CNC] Horizontal Planes

You need a Precision Machinists' Level like this;

http://catalog.starrett.com/catalog/catalog/groupf.asp?groupid=88

Another way is to use an autocollimator. Ordinary autollimators
can measure angles down to 1 arc second. They often appear on ebay for
$100 to $500.

Here is one.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230002552064

Here is another model;
http://www.davidsonoptronics.com/catD-638.htm

Autocollimators are how machine tool manufacturers measure
the flatness of the machine beds on larger machines. They can work over
distances of hundreds of feet.

An autocollimator is sort of a specialized telescope. It is able to
accurately
measure the angle of a target mirror. The target mirror can be hundreds
of feet away. You move the target mirror around your table and measure
the angle at various points.

Here is a better explanation of how they work;
http://www.davidsonoptronics.com/poa.htm

Pete.

----- Original Message -----
From: "Tyson S." <timbercutter@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>; <CNCrouters@yahoogroups.com>;
<DIY-CNC@yahoogroups.com>; <hobbymachine@yahoogroups.com>;
<home_machinist@yahoogroups.com>
Sent: Tuesday, July 04, 2006 2:06 AM
Subject: [DIY-CNC] Horizontal Planes


> Sorry for the multiple list posting, but it is a question concerning
> CNC machines, fabrication, and precision. I have posted a picture that
> I drew which should help explain the situation a bit more. I am looking
> for a good way to check for flatness of a frame that will be the CNC
> table. The image is here, http://webpages.charter.net/aprs/level.JPG
> and basically out of all the possible measurements one can make to an
> object ,this is the only one you can not use a tape measure on. I
> bought an expensive, brand new Starret StaTru bubble level thinking
> that would be the ticket to use by checking both ends of the frame,
> well, other than the pretty shiny red powder coat finish on the level
> it ain't no better than what you could buy at the local hardware store,
> sad. So is there any old school method that they maybe used when making
> aircraft by hand in 1942 or something?
>
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