High Precision Measurement in 1952?
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    Default High Precision Measurement in 1952?

    Yes the Metrology or maybe the Antique Machinery and History sub forums might be a better place to post a question like this. But this general forum gets many more views with a much more experienced and diverse audience. Roughly 8 years ago I was sent this sine bar by a total stranger. Pictures in this link. What Is This - The Home Machinist! And given it's build location (Los Alamos N.M) it would be safe to assume they had what would have been the very best state of the art measuring equipment available in 1952. More out of curiosity than an actual need to know, I've tried a few times with a couple of YouTube video posters that seem to have a good back round in metrology and it's more modern history about what Los Alamos might have used to measure the roll distance with a certainty of 5 decimal places. So far that's been a total failure.The original poor condition paperwork and signed by I'd assume the person who measured it shows that roll spacing as being exactly + 5.00034". Anyone old enough or knowledgeable care to make some semi educated guesses about what they might have used? Gauge blocks and a very good high accuracy indicator on a height gauge / surface plate might have been been all that was required. But I honestly don't really know what else a place like Los Alamos might have had available to them during that time period to make high precision measurements. Fwiw and since there's absolutely no marks or even a scratch on this sine bar I don't believe it's ever been used for it's intended purpose. It's still in it's original 1952 condition. And R.D. Marlett whoever he was did a beautiful job on it. As well made as my 5" Suburban sine bar is it's not even close to this one.

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    The surface plate, gage blocks and a very precise indicator mounted on a stout height transfer stand would be my first guess.

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    Quote Originally Posted by neanderthal mach View Post
    Yes the Metrology or maybe the Antique Machinery and History sub forums might be a better place to post a question like this. But this general forum gets many more views with a much more experienced and diverse audience. Roughly 8 years ago I was sent this sine bar by a total stranger. Pictures in this link. What Is This - The Home Machinist! And given it's build location (Los Alamos N.M) it would be safe to assume they had what would have been the very best state of the art measuring equipment available in 1952. More out of curiosity than an actual need to know, I've tried a few times with a couple of YouTube video posters that seem to have a good back round in metrology and it's more modern history about what Los Alamos might have used to measure the roll distance with a certainty of 5 decimal places. So far that's been a total failure.The original poor condition paperwork and signed by I'd assume the person who measured it shows that roll spacing as being exactly + 5.00034". Anyone old enough or knowledgeable care to make some semi educated guesses about what they might have used? Gauge blocks and a very good high accuracy indicator on a height gauge / surface plate might have been been all that was required. But I honestly don't really know what else a place like Los Alamos might have had available to them during that time period to make high precision measurements. Fwiw and since there's absolutely no marks or even a scratch on this sine bar I don't believe it's ever been used for it's intended purpose. It's still in it's original 1952 condition. And R.D. Marlett whoever he was did a beautiful job on it. As well made as my 5" Suburban sine bar is it's not even close to this one.
    "Laboratory" or standards grade surface plates were already old news. Ditto "clean rooms" and temp control.

    Hamilton - "the Watch people", and one of several "first order" national technology "treasures" - were delivering superbly built 4 AGD DI's with ten-millionths per division already. They sold that production line to Dorsey Gauge, who took the staff onboard and kept on making them, "Dorsey" labeled or branded for Pratt & Whitney.

    Mine is an original "Hamilton".

    The Height stand?

    Possibly one of Weber (Starrett) Digi-Check, B&S Height-Icator, Cadillac Gauge (the armoured-car folks- combat type, not bank delivery type..) "Pla-Chek".

    I have one of each. The metrology. Not the armoured vehicle.

    And easily as old, a set of "Dearborn Gage" (C. E. Johansson + Henry Ford, 1923 onward..) blocks, with a few DoAll or Weber filling-in.

    Yah. Folks could do this stuff.

    And a LOT earlier than the 1950's.



    Los Alibis labs - and "not only" ... a host of other top-end defense & R&D establishments would have had ANYthing they needed.

    Even if it had to be invented for their purposes.

    And "Oh, BTW?"

    Damn
    the cost!

    USA, pre Obama/Biden, had less than ZERO interest in coming out "second place winner..... in a gunfight".

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    The moore books (from that era) talk about electric indicators with 5 millionths precision, and they mention in passing that mechanical indicators that precise do exist, but are finicky. I have the dorsey version of the hamilton Thermite mentions, and measuring to 10 or 20 millionths is always fiddly to begin with.

    The following link suggests that things very similar to modern LVDTs were proposed by the mid 1930s and pretty well through out by the 1940s - it would be quite plausible for somebody at the labs to have access to an LVDT.
    sensors:linear_variable_differential_transformer [SensorWiki.org]


    Recall that at least in principle, LVDTs have infinite resoution.... (But the counter heads I can find online seem to never be speced below 5millionths or 100nanometers... ish.)

    And of course, you could compute the spit between the sine bar rollers by setting with good gauge blocks, then carefully measuring the resulting angle (same sorts of instruments) - and given the exact angle a particular set of "perfect" gauge blocks produced, you could compute what the spacing of the rollers would have to be.

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    Just a side note: You may want to check that sine bar with a Geiger counter, in case it actually got used for setups in machining the facets on U-235 or plutonium sphere segments. That work may have moved to other locations by that time (1952), but there was an awful lot of R&D going on at Los Alamos in any case.

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    Many thanks Bryan,I've got two of the Moore books so thanks for the memory jog. Moore was according to one of them reliably measuring to low millionths for there trial experiments with ground and lapped feed screws and nuts around that approximate date just as you said.While I hadn't known about that LVDT technology that's certainly a real possibility. I'm unsure when high resolution gauge head amplifier's were commonly available, but after your comments then quite likely before it's 1952 date. This is at least 7 years after the first bomb so they certainly had far higher precision prior to when it was first measured. And yes you could certainly compute it's roll spacing in just the way you mentioned. My math knowledge doesn't go that far so it's a method I hadn't even considered. For sure I should have posted this question here years ago, I knew you guys would come through like usual. I did contact Los Alamos a few years ago, but the people there today or at least who I talked to didn't have any idea how it might have been measured, nor did the woman in there museum either.

    A worthwhile warning Specfab, but as I said there's not a scratch on it so extremely doubtful it's ever been used. And since this would have been taken through the security gate at Los Alamos and much later shipped out of the U.S. and up to me in Western Canaduh anything active enough to trip a geiger counter very far wouldn't have gotten out of Los Alamos or through customs today. Since it was made at Los Alamos it would be a pretty safe bet it might be a little higher in radiation than anything else I have. It doesn't glow in the dark at least.

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    neanderthal - "commonly available" and "in hand in the national labs" don't actually have much to do with each other. for 1950's los alamos to have the best, or the only, or one of only 5 known to exist, of this that or the other instrument would expected. hence, i wouldn't be surprized if there were first rate LVDT's there by 1950, even there were none elsewhere in the world.

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    I would guess interferometer as most accurate. I think it is within one angstrom. Certainly in use in 1950.
    Bill D

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    You could broaden your outlook with such as pubs as Accurate Tool Work .... from 1912 .....by Goodrich and Stanley

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    Distance (rolls being measured + 5.00034" between seats) is one of 6 variables, with the roll to bar being the other you can account for. 3½ tenths in 5 inch length (for the way these things were usually actually made & used) is really-really good.

    There’s a couple of things going on for making a sine bar… First is to prove the rolls are on size and really round… Then also proving the rounds are at the desired distance & the top of the sine bar is the same height with the rolls affixed, then last, no axis got twisted. It's not a small deal.

    Making a sine bar you can screw up 6 discrete ways (3 axis freedoms = 3 rotations + 3 distances)??? If we take (all) angle rotations out (hard to solve in the shop), geometric tables have been published far exceeding 5 places forever. If you chose to calculate to closer than the published (5-7 place) decimals, there are angles (close) that DO resolve without a never ending remainder and you can reconcile (closer by ratio) to see if the tool you made is good enough to do the job.

    BTW, that’s a cool tool & appears well done.

    Good luck
    Matt

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    My dad has, for some a reason, a really old Rank Taylor Hobson LVDT amplifier. I never knew what it was until quite recently when I bought a modern one myself. It never had any probes with it, so it wasn't obvious what it was to me at the time. He doesn't know where he got. I don't think it's from a Talyrond or Talysurf as those had specific markings or badges for those machines as far as I can tell.

    I can't find a picture on google of a unit quite like it.

    I haven't laid eyes on it in a few years so fuzzy memory etc.

    It looks aesthetically like a WW2 era piece of equipment, but I specifically remember that it has the Rank Taylor Hobson branding, which according to wikipedia would date it after 1946 when TH was absorbed into Rank. I can't remember what it's graduations are.

    Point being, it does seem like those would have been generally available to those with the means to purchase in 1952, and used comparatively with gauge blocks would provide the required precision.

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    Bill D is right - interferometers date from at least the 1890s - Michelson-Morley experiment involves a kind of interferometer sometimes called Michelson interferometer.
    There's a NIST paper on gauge blocks where they talk about the lab used to measure and compare them, seems that they had been using the same Michelson interferometer for this purpose since the '30s. (No reason to change, change introduces errors...)
    [This is the paper where they point out that steel evaporates - at a rate it takes decades with an interferometer to detect, but...]

    Bad title - Wikipedia

    Unlikely that level of technology would have been applies to sine bar, but you never know.

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    Wow, I'm impressed with the response this got and many many thanks to everyone for there input and years of knowledge. I very much appreciate it since I've learned a lot. Any of the methods you've all mentioned are older technology than I'd thought so there's multiple ways this could have been measured to higher accuracy than even the paper work shows. And your quite right Bryan, if anybody had it or even if it needed to be invented then Los Alamos would been one of the first. Thanks for the book recommendation for the Accurate Tool Work John, I'll have to hunt down a copy. I have another Goodrich and Stanley book titled Tool and Gage Work first published in 1907. There's a whole chapter devoted to what must have been the very first set of C.E. Johansson gauge blocks in America. There speculations about how they might be used in the future proved to be pretty much dead on. I've always been curious about how C.E.J. measured his gauge blocks and your point Bryan about interferometers being available since the 1890's just might be a hint for how it was done.

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    Em..
    Moore today says their gage blocks are lapped to 0.01 microns. It´s noted somewhere.

    Endless hobby astronomers lap lenses and glass flats to about 0.1 microns, or better.
    Hand lapping can produce these kinds of sizes/tolerances/flats using the right technique, and a trivial 50$ in kit.

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    Quote Originally Posted by hanermo View Post
    Em..
    Moore today says their gage blocks are lapped to 0.01 microns. It´s noted somewhere.

    Endless hobby astronomers lap lenses and glass flats to about 0.1 microns, or better.
    Hand lapping can produce these kinds of sizes/tolerances/flats using the right technique, and a trivial 50$ in kit.
    The question was a specific distance and 5 place tolerance. You aren't going to measure that for $50, unless you stumble on some auction find.

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    Quote Originally Posted by Hillside Fab View Post
    The question was a specific distance and 5 place tolerance. You aren't going to measure that for $50, unless you stumble on some auction find.
    When you start talking of measurements in the millionths of an inch, it's not just the kit, but the rigor of how you manage thermal loads (including stray light), humidity, air currents, human proximity, etc.

    I'm grateful that most of the work I do stays in the .001" range usually. Saves some of the remaining hair...

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    Quote Originally Posted by Milland View Post
    When you start talking of measurements in the millionths of an inch, it's not just the kit, but the rigor of how you manage thermal loads (including stray light), humidity, air currents, human proximity, etc.

    I'm grateful that most of the work I do stays in the .001" range usually. Saves some of the remaining hair...
    I dont work for NIST, but on a steel part, holding the temp consistent with the measuring equipment should be enough.


    You have to have an accurate reference, repeatable measuring tools, and thermal stability. And for millionths on a 5" long part that's expensive. It's also expensive for tenths on a 2ft" part. And it's also expensive for thousandths on a 10ft+ part.

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    Expensive? I'll say.More out of curiosity than anything else I've thought about trying to remeasure the roll spacing on this. Unfortunately I doubt I could do so well enough to have any meaningful numbers. Mitutoyo did tell me that even there steel gauge blocks can change up to + - 1 um per inch / per year. And while it's been almost 7 decades since it was built, nothing I own is going to come close to measuring Bryan's detail about steel slowly evaporating over those decades. I do have a 20 millionths capable millimess, NOS condition Mit. grade two gauge blocks, what I think is a more than rigid enough height gauge and a dubious certificate of flatness for an off shore surface plate. But no temperature control. At best on a good day I'm thinking that letting everything thermally stabilize on the surface plate for 24 hrs I might get within a 10th or two. Even then I couldn't be absolutely certain of exactly which 10th it might be. To 5 decimal places, what I have isn't even in the ball park.

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    Quote Originally Posted by neanderthal mach View Post
    Expensive? I'll say.More out of curiosity than anything else I've thought about trying to remeasure the roll spacing on this. Unfortunately I doubt I could do so well enough to have any meaningful numbers. Mitutoyo did tell me that even there steel gauge blocks can change up to + - 1 um per inch / per year. And while it's been almost 7 decades since it was built, nothing I own is going to come close to measuring Bryan's detail about steel slowly evaporating over those decades. I do have a 20 millionths capable millimess, NOS condition Mit. grade two gauge blocks, what I think is a more than rigid enough height gauge and a dubious certificate of flatness for an off shore surface plate. But no temperature control. At best on a good day I'm thinking that letting everything thermally stabilize on the surface plate for 24 hrs I might get within a 10th or two. Even then I couldn't be absolutely certain of exactly which 10th it might be. To 5 decimal places, what I have isn't even in the ball park.
    I think you are over complicating it a bit. I dont work to these tolerances, but I'm pretty confident you can get gage blocks calibrated by a lab for what you are asking about relatively easily. Then you just need a good indicator, and thermal stability. (still a lot more than $50)

    The idea is that your gage blocks and parts have to be the same temp, negating any effects of thermal expansion (or being able to calculate for different expansion rates). Your measuring tool is just comparing your part to a known good reference.


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