How is it possible to scribe lines within 0.0005" precision? - Page 3
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  1. #41
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    I don't think that kind of precision is possible but when I need to do accurate layout by hand I use a surface plate, square, and an old Starrett vernier height gauge with scriber. The trick is to make sure the edges are straight and identify a corner that is exactly 90 degrees.

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    Does anyone have one of thos "L.S. Starrett Commemorative Punch Hammers"?

    The ones with the built in magnification glass...

    Close work needs every help it can get.

    L.S. Starrett knew his shit.

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    Quote Originally Posted by thermite View Post
    "Originally, high-resolution gratings were ruled by high-quality ruling engines whose construction was a large undertaking. Henry Joseph Grayson designed a machine to make diffraction gratings, succeeding with one of 120,000 lines to the inch (approx. 4,724 lines per mm) in 1899."



    jscpm asked about TWO THOUSAND lines to the inch.

    Grayson was ruling to ONE-SIXTIETH of that ....... 122 years ago.

    Diffraction grating - Wikipedia

    Don't tell me you "cannot". You can. JF go and try it
    thermite, you know perfectly well that running a ruling engine and manual layout are two totally different procefures. So please don't go tossing around difraction gratings as if there were any Earthly chance of a human working to that scale. That's too silly, even for you.
    Last edited by sfriedberg; 05-02-2021 at 03:54 AM.

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    Quote Originally Posted by sfriedberg View Post
    thermite, you know perfectly well that running a ruling engine and manual layout are two totally different proceures. So please don't go tossing around difraction gratings as if there were any Earthly chance of a human working to that scale. That's too silly, even for you.
    I haven't ever needed to get anywhere NEAR 120,000 lines to the inch yet, either, genius.

    But if Grayson can do one line many times, one line one time at one-sixtieth of his granularity will do just fine, thanks!

    And some of you getting older-faster-than-I-am deniers of reality wonder why I put you on "ignore"?

    Right about when your brains go fossilized and you start to deny historical accomplishments of OTHERS in-the-record and in past-practice who went before us .... because YOU can no longer be bothered to even ATTEMPT to do what so many others already HAD DONE is when!

    Dunno is that is actually senility ... or just plain sloth?

    But "denial" is NOT a positive force for a future.

    Grayson y'see.. had competition.

    So do we!

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    Quote Originally Posted by thermite View Post
    But if Grayson can do one line many times, one line one time at one-sixtieth of his granularity will do just fine, thanks!
    No, see, that's exactly what I was talking about. There is no sensible way to use the properties of a ruling engine to make some assertion that a human can do the same thing, if they only have to do it once. If you're going to talk nonsense, expect to get called on it.

  6. #46
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    I think people are overthinking this a little with diffraction gratings, etc. All we are trying to do here is make some controlled scratches.

    Obviously, it could be done just by trial and error. Draw the scribe across the surface lightly, then press a little harder and so on. Just make a whole lot of scratches and try to luck out with getting ones of the depth wanted. I am hoping for something more systematic, maybe using a spring contraption of some kind.

    As far as measuring the scratches, it is easy to do this with a metallographic microscope. Most such microscopes easily resolve +/- 1 Mm which is more than enough precision for what is needed.

  7. #47
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    Em..
    endless manual watchmakers, past, and modern tinkerers scribe lines and make parts to accuracies of 0.01 mm == 0.0004".
    They don´t usually work to the lines, the lines are just a guide to make sure they are on the right track.

    Like Model engine makers.
    And those can be accuracies rather than resolutions.

    It´s perfectly possible, and not too hard, to make smallish parts accurate to 0.01 mm, by hand.
    0.005 " accurate, half a thou.

    Endless amateur telescope makers make complex curved mirrors to better than 1 micron or 0.001 mm or 0.000 04" accuracies, often several times better.

    A 40$ manual lighted lense will make easy tracking and marking bits to better than 0.1 mm, approaching 0.05 mm or better.
    So will a small usb microscope.
    Positioning to 0.05 mm, approaching better, is not that hard to do with basic manual equipment.
    Using a newer microscope with integrated display may make it easier yet, haven´t tried it.

    *Positioning* (not accuracy) to +/- 1 micron is perfectly possible for anyone with the ability to spend 70$ each on 3 Tellabs differential positioning screws, like I did.
    (Tellabs, others) Differential screws are guaranteed to position stuff to 0.5 microns, or one half of ten thousandths.

    So anyhone can move a drill bushing under the usb scope or manual lens until it is centered very precisely across a fine scribed line.
    Positioning accuracies of about 0.01 mm or 0.0005" are probably perfectly feasible, even when based on lines.
    Just because the line is much wider than 0.01 mm does not make it hard to center an object across it, under magnification.

    The cheap plastic rule/scale I have for the lens is good to 0.05 mm, and much finer positioning is easy to do between the lines.

    Again, people making instruments and clocks routinely make 0.01 mm or better accuracies in positioning pinions, gears, and stuff from one to the other.

    I doubt making very fine lines is hard at all.

    Suggestion:
    Buy some butterfly needles, they come in very small sizes.
    Epoxy one to a handle of choice, done.
    1$.

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  9. #48
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    There is a big difference between scribing a line and then machining them to half a thou, and scribing a line and having it within half a thou. Everyone here has rough machined to scribed lines and then using the appropriate measuring strategy, machined to tolerance. I do it for a sanity check so I do not get carried away with the numbers in my head and wreck the part by making an obvious mistake.

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    When I have sought to scribe a fine line, I generally use a fresh Exacto knife blade and drag it along a straight edge. Of course, that quickly serves to illustrate that even my best straight edges have all sorts of little bumps, burrs, and nicks along them.

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    Quote Originally Posted by GregSY View Post
    When I have sought to scribe a fine line, I generally use a fresh Exacto knife blade and drag it along a straight edge. Of course, that quickly serves to illustrate that even my best straight edges have all sorts of little bumps, burrs, and nicks along them.
    none larger than a harf a thou tho..........

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    Quote Originally Posted by jscpm View Post
    A problem I run into occasionally is scribing lines precisely enough when doing layout. When using straightedges and an ordinary carbide scriber I find that I get about five thousandths precision (+/- 0.005") whereas I would really like to be more within five tenths (+/- 0.0005") of the target dimension.

    For example, let's say I have two pins and I want to scribe a line tangential to the two pins. If I lay a straightedge against the pins and scribe the lines along the straightedge I find it difficult to get within tenths of the true tangent.

    How is it possible for me to up my game and get my lines tighter?
    It appears to me that your understanding of machining is pretty much right up there with your understanding of everything else that you have posted here. I suggest that you start by repeating kindergarten and going from there.

    Your scribe line is likely wider than .0005".

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  16. #52
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    Quote Originally Posted by Big B View Post
    Your scribe line is likely wider than .0005".
    For sure but you can use one base edge of the line in which case .010/.020 thou wide is of no matter....
    Bob

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    Quote Originally Posted by Big B View Post
    It appears to me that your understanding of machining is pretty much right up there with your understanding of everything else that you have posted here. I suggest that you start by repeating kindergarten and going from there.

    Your scribe line is likely wider than .0005".
    The tip of a high quality scriber is about 0.0005" in diameter.

    Do you insult and abuse your employees as much as the people on this forum?

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  19. #54
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    Quote Originally Posted by jscpm View Post
    The tip of a high quality scriber is about 0.0005" in diameter.

    Do you insult and abuse your employees as much as the people on this forum?
    The point being that in order to have a half thou precision, one would need a much smaller line, and be able to place it more accurately, and then locate it with a cutting tool more accurately.

    Scribing as an actual defining dimension, is adequate for sheet metal work where the dimensions are in fractions.

    So, no, you do not understand the concept of precision.

    My Lagun manual can drill holes when set up carefully and operated as such, that I cannot measure error in with calipers up to 24 inch

    That does not mean they are within half a thou.

    But it means they are probably close enough

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    Quote Originally Posted by jscpm View Post
    The tip of a high quality scriber is about 0.0005" in diameter.
    Speciality goods, of course, exist. The problem is that absent equipment to work WITH them you are aready into "diminishing returns."

    For an emergency, one can TAKE ten times as long to do a thing that only needs done very, very rarely. If there s any regular need, OTOH, better methods will save money. Modern labour costs are NOT all that cheap.

    Pragmatically, I try to not push beyond what I can scribe with a phonograph needle. Not the smallest of scribers, no.

    But for every-day use a very small spend will get them by the multiple hundreds to the tin. A "fresh" one is cheap and ever-handy.

    Herr Pelz ethic:

    Any thing a good man can do, another good man can duplicate and a BETTER man can improve."

    Naturally, he wanted each of us to "become" that "better" man!
    Didn't seem like a BAD idea... so we tried.

    When one HAS to do a thing? Just find a way and do it.


    Do you insult and abuse your employees as much as the people on this forum?
    Whom? Big Bidet? Check his post history. None here are "perfect", least of all me.
    But he'll serve as a damned good imitation of more insults that help until the rioters arrive to loot and burn, yah?


  21. #56
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    termite, you are a fake, fraud, and a worthless piece of shit.
    You have never worked as a machinist, and it shows in your long stupid post.
    You have no running machines, or have displayed any metal work, at all in the entire time you have been here.
    You have been checked out by senior members as a bull shitter, but you keep going because you are addicted to posting everyday, you have to protect the pile of lies you laid out here.
    I have warned you many times, to stay away from my post, and threads, and stay in the Monarch forum that you have trashed already.
    Its like this termite, you have, and have used many other fake names on this forum. You better kill off your "termite" ID!

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  23. #57
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    Quote Originally Posted by donie View Post
    termite, you are a fake, fraud, and a worthless piece of shit.
    You have never worked as a machinist, and it shows in your long stupid post.
    You have no running machines, or have displayed any metal work, at all in the entire time you have been here.
    You have been checked out by senior members as a bull shitter, but you keep going because you are addicted to posting everyday, you have to protect the pile of lies you laid out here.
    I have warned you many times, to stay away from my post, and threads, and stay in the Monarch forum that you have trashed already.
    Its like this termite, you have, and have used many other fake names on this forum. You better kill off your "termite" ID!

    What a prize prat.

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  25. #58
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    I should ask if we are talking about a hand held scribing "pen" or a scribe tip as used on on height gauge layout?
    Will ignore the hand held and draw a line. Height gauge and you use the corner of the tool. Even in carbide the base of the line moves with use.
    Done right I can see machine work done to handful of thou. I'd guess .003-.005.
    Such lines are so great as a sanity check. I do it often and has saved my butt from some brain dead oops. Why am I another near this line? What did i blow?

    I thing making scribed lines within .0005 is entirety double. .
    Bob

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    Quote Originally Posted by camscan View Post
    What a prize prat.
    Yes, I think it's becoming obvious who keeps fanning the flames of this feud.

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  28. #60
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    Far as I can tell nobody's actually scribed a layout line on a blued part, and then measured it under a microscope.

    So basically an entire thread about how many angels can dance on the head of a scriber point.

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