Re: [CAD_CAM_EDM_DRO] Horizontal Planes

Hi Tyson: I know and easy and low cost way of checking it to within
a .001 at all four corners. You can get it within the width of a
line (.005-.015) with just a simple water lever like they use for
checking cement footing or foundation forms. The key is to calibrate
the two tubs on a level surface at the start. Use your best level
you have and check a surface large enough to hold the vertical tubes
of the water level side by side. When you feel the surface is level
turn the level around 180 degrees and double check the level to see
how accurate it was. If it reads the same both ways the surface is
level. Now fill the water level (carefully without bubbles) then put
the the two water level tubes in there bases on the level surface
side by side. Check to see were the water level is in both tubes.
if it is not near a line in both of the tubes add a few drops of
water with a dropper until the water in one or both of the tubes is
even at the top or bottom of a line. Be sure to use just the top
edge of the water were it wets up the side of the tube. Now if both
of the tubes do not come out even on the line slide a piece of paper
under the lowest one and add water till you get both units right on
the same edge of the line. Note: a good machinist uses cigarette
paper for close shims as it is .001 thick. Now you have a tool that
you can put one tube at one corner and check the other corners to it.
In this way you can get all four corner close. (approx .005 to .010
if you are careful)
Now for the old time trick!!! If you need to get it even closer
put some salt in the water and put a shallow tin can (solder on a
small tube for the hose) on each end of the hose instead of the clear
tubes with bases. Now using a couple of parallel or blocks on one on
each side of the tin can you can use a depth mike to measure the
water level. To get even more accurate use a battery and light and
run the current through the water as one side of the circuit and a
wire for the second side so that when the micrometer which is one end
of the circuit touches the water it closes the circuit and the light
comes on. This will get you within a .001 if you do it carefully.
Note: if you are working on round ways use a pare of matching vee
blocks or secure the depth micrometer to a single one with a clamp.
I hope this helps. Is this clear as mud? If it is ask me questions
on what you don't understand.
GOD'S BLESSINGS
Bill





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From: "Tyson S." <timbercutter@...>
Date sent: Mon, 3 Jul 2006 23:06:39 -0700 (PDT)
Subject: [CAD_CAM_EDM_DRO] Horizontal Planes
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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?