What sort of surface plate is this?

I've just posted a picture in

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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?

Reply to
stu
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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

Reply to
pentagrid

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)
Reply to
stu

YOu could probably sell that and use the money to get a good granite surface place and have change left for a cup of coffee or two. :)

Its way overkill for most anything you would normally want to do unless you wanted to make yourself a set of "A" quality precision gauge blocks.

John

Reply to
john

I've seen one, they are glass. Not sure what you have.

Thank You, Randy

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Reply to
Randy

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.

Reply to
pentagrid

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

Reply to
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40 years out of date, was to qualify custom gages that were used in production manufacturing -- go/no-go snap gages and so on.
Reply to
Ed Huntress

To another stack for comparison? Please clarify, I'm still in learning mode tonight :)

Oh, since I detest the lack of proper http links,

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Wes

Reply to
Wes

If you have a set of certified blocks, you can make transfers from them to something else (a custom gage, a height gage, an electronic indicator, etc.) and rely on the transferred dimension -- with the allowed tolerances of the first set of gage blocks plus that of the plate.

The surfaces of these plates are lapped similarly to the gage surfaces of gage blocks. You can apply the certified flatness of the plate, add the cert. range of the gage blocks, and then document that height (assuming you'd done scheduled certs. on the gage blocks) for reporting to a customer; even a very demanding one.

A big plate like the ones that Stu has may not be in the 2 - 4 millionths range of the smallest ones, but whatever it is, you can apply that certified accuracy to your gaging.

Reply to
Ed Huntress

I wasn't sure that direct links was the done thing. Thanks

Reply to
stu

There are a lot of links on Usenet, many I wouldn't click on if I didn't know the target. If I can be as bold as saying this, we tend to trust the metalworking.com Dropbox. Most of us are not link happy newbies just experiencing the Internet so adding the full link to that site is just fine and saves a bit of time.

Wes

Reply to
Wes

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.

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

Reply to
stu

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.

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?

Reply to
Ed Huntress
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Actually -- they are quartz, not glass.

Still fully transparent -- and typically labeled around the edge.

Enjoy, DoN.

Reply to
DoN. Nichols

I've uploaded a couple of pictures of the large plate after a quick clean wipe of kero.

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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.

Reply to
stu

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.

Reply to
Ed Huntress

A flat like this can also be used to set the zero of lapping fixtures like these:

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. It can also be used for things like setting the zero of a flatness gauge used to qualify lapping plates and surface plates:
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although the spherical contacts might scratch a metal flat.

Reply to
anorton

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Interesting stuff. Precision lapping is quite an art. We used to have a member here who had quite a bit of experience with it, years ago.

Reply to
Ed Huntress

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I am hardly an expert, but I do have a Lapmaster-12 machine in my garage. Optical engineering is my profession and I want to convert it to polish glass.

Reply to
anorton

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