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On Sun, 14 Mar 2010 00:55:03 +1100, "stu" no where just yet
wrote:


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news:cu3np5la85p48d0vchp58tos9do4fun5me@ 4ax.com...
On Sat, 13 Mar 2010 20:55:17 +1100, "stu" no where just yet
wrote:

I've just posted a picture in
http://www.metalworking.com/Dropbox called
"stusplate"(is it the done thing to put a direct link here?)
As you can see from the reflection of newpaper, the surface has
a very
fine
finish like no surface plate I have ever seen. It comes in a
felt lined
lockable box. Does anyone have any idea what this sort of plate
is?

Could be an optical flat. Your jpg doesn't show the size.
Inspection grade optical flats are typically 5 or 6" dia and
polished flat to within a fraction of the wavelength of green
light.

Jim
So that would be pretty flat then lol
I have two, one is 170mm(7inches) x 35mm(1.5inches) thick. The
other is
220mm(9inches) x 35mm(1.5inches)they are labeled "precison plate"
I thought about optical flats but I thought they were made from
glass?(although I'm not even sure I've ever seen an optical flat)

Most optical flats are glass or quartz. I have a 6"dia x 1/2"
glass flat. Although your flats are opaque, bearing in mind the
polish, the thickness and the careful packaging, I still think
they are likely to be flat to optical precision standard

Jim.

Stu has a couple of toolmaker's flats. They're made with a surface
that allows a gage block to be wrung to the surface, so that clamps
aren't needed. It's frequently used in gage labs for qualifying and
certifying instruments. Standard sizes are 2" and 4", so Stu's are
something pretty special. I've seen them that big, though, in
Mitutoyo's qualification lab.

If you keep that surface scratch-free, there's no better way to set
up a stack of gage blocks to extreme, certifiable, transferable
accuracy.

--
Ed Huntress

BTW, I should mention that their original purpose, which is now
about 30 or 40 years out of date, was to qualify custom gages that
were used in production manufacturing -- go/no-go snap gages and so
on.

--
Ed Huntress

Thanks Ed (and others)
There are some light scratches in the small one, just behind the
person it the photo. I didn't do a very good job cleaning the block
as I wasn't sure what to use. I'm yet to clean the large one, I'll
try to get onto it this evening, but what to use? I'm guessing "kero
and a rag" aren't the done thing.

Kero and a rag isn't bad at all. Don't use anything the least bit
abrasive or corrosive to steel. No Windex. Then lightly oil it with a
rag and put it away. Wipe the oil off before using. If you're going to
try wringing gage blocks against them, clean with a solvent on the
working surface, really well, first. Paint thinner should do it.


I believe you are right about the "production manufacturing ", they
have a name plate from a wire company where I am guessing they were
used, but they have no other name on them.

I'm try and get some more info on here tonight.
thanks again

Stu

You're welcome, Stu. They're interesting tools and they don't take up
much room. With scratches, you probably won't get much for them, so
you'd might as well keep them.

Do you have a set of gage blocks?

--
Ed Huntress
I've uploaded a couple of pictures of the large plate after a quick
clean wipe of kero.
http://www.metalworking.com/Dropbox/stusplatelarge.jpg
http://www.metalworking.com/Dropbox/stusplatelargeb.jpg
as you can see the isnt as good as the small one. I would think that it
is still plenty good enough for me. It will be nice to have something
"flat" in the shed, even if it is a little over the top.

I dont have gauge blocks yet although I am keeping an eye out for some,
I cant really think of an excuse to buy a new set.

You may or may not have a need for them, depending upon the kind of work
you do. I don't think most hobbyists need a full set of gage blocks, but
I do find use for a few very good ones, to check my mikes, calipers, and
height gage.

But those plates you have are not something any of us would really need,
either. They're nice to have. You can get some use out of them, but it's
unlikely you'll be qualifying gages or making production gages. g

--
Ed Huntress

Very interesting info guys. I was thinking about spotting them with
bearing blue to see how close to each other they are. There wouldn't be a
problem with that would there?

As far as needing gauge blocks goes. All of my work so far(very limited
and not in the same league accuracy wise) is what I call "comparison
measuring", so my mic's could be calibrated in westernwigets for all it
matters. As long as they are consistent.


I would not try that. You want to minimize sliding of anything on top of
these to prevent scratches. Besides, it will not tell you much. These
plates should be flat to better than 300 nanometers which is probably a
little thinner than the dye layer. You really need optical methods to test
them. If you are interested, google "making optical flats", some of those
pages outline test methods an amateur can do.

That's true. My suggestion of using rouge is probably of no use on such flat
surfaces.

--
Ed Huntress