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Thread: cave/poor man's accurate cylinder

  1. #1
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    cave/poor man's accurate cylinder

    Hi there, I might have asked a similar thing years ago. This one is more specific.

    How can one make a mechanically accurate cylinder with cylinder specifications and only available tools listed below:

    1) cylinder specs: steel, 24cm long, 8cm diameter (material preference: regular steel)

    (numbers are approximate, don't be concerned with units at the moment, important thing is accuracy)

    2) surface plate(s)

    3) any "crude" non-accurate things required will be provided

    (for example, want a steel hammer? here you go, a nice hand carved steel hammer )

    (want a cylinder as a start? here you go, a nice hand carved steel cylinder of about 24cm long and 8cm diameter)

    I have read gingery book, although it starts promising, it quickly grows out of control and starts using modern accurate tools.
    For years I have been looking for a method to make accurate cylinders without having to derive accuracy from other tool.
    Just like a method to make flat surface, is there a method to make accurate cylinder ?
    (the roundness and cylindricity are most important for me, the ends of cylinder are not, for now, so flatness and perpendicularity of the ends are not of concern at the moment)

  2. #2
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    Do you allow a compass or string to draw a circle?
    Do you allow a hand drawn circle?
    Do you want to work from a lump of steel?
    Or can the steel be cast?
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  3. #3
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    Quote Originally Posted by profloater View Post
    Do you allow a compass or string to draw a circle?
    Do you allow a hand drawn circle?
    Do you want to work from a lump of steel?
    Or can the steel be cast?
    1. compass does, two pointy ends that keep at constant distance: can be made manually, allowed.
    2. hand drawn circle: allowed
    3. yes lump of steel is allowed, lot's of common abundant natural materials available, steel/iron lumps already smelted from ore.
    4. casting allowed as long as the pattern is not made using already accurate modern tools.

    extra:
    5. granite/ cast iron surface plate(s) already made
    Last edited by roboticmhd; 2019-Sep-17 at 07:08 PM.

  4. #4
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    Do you disallow making the tool to make the thing?
    Say, a hand-operated lathe?
    You could surely make the entire thing out of wood.

    History-Of-The-Lathe-287.png

  5. #5
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    Steel is tough to work so you you need time but sand will wear it away with any rubbing block such as wood or cork. You make a gauge like a three tooth comb to define the radius, teeth make good points. Where the centre tooth touches you wear away. As accuracy improves use a “blue” made of grease and pigment, this can easily achieve 0.0001 inch accuracy. When a part is ready you can cast off a pattern using clay, this will speed up production but sanding will take a long time. The flat plate will help extend the rounded area along the length. But a straight edge would do. There is a risk of making constant diameters instead of circles but a series of three tooth gauges of different sizes help with that. Geometry knowledge will help make the gauges but you said absolute dimension is less critical than accuracy of shape. This is a cave man version of centreless grinding! For the gauges use the intersecting chord theorem to set the teeth. If you can heat the steel the roughing can be done by hitting with hammers on a flat anvil, but the final accuracy is with polish and blue. The polish can be made from diamonds. Does that work for you?
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  6. #6
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    You Don't

    Is this a homework question from a machine shop class?

  7. #7
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    Don't want the topic to die out, I am trying to understand what you wrote profloater. Can you please explain in more detail, some simple drawing perhaps, if you have time?

    From what I understood, are you suggesting to make a circle, somehow, then somehow extend it ? I might be wrong

    "Steel is tough to work so you you need time but sand will wear it away with any rubbing block such as wood or cork. You make a gauge like a three tooth comb to define the radius, teeth make good points. Where the centre tooth touches you wear away. As accuracy improves use a “blue” made of grease and pigment, this can easily achieve 0.0001 inch accuracy. When a part is ready you can cast off a pattern using clay, this will speed up production but sanding will take a long time. The flat plate will help extend the rounded area along the length. But a straight edge would do. There is a risk of making constant diameters instead of circles but a series of three tooth gauges of different sizes help with that. Geometry knowledge will help make the gauges but you said absolute dimension is less critical than accuracy of shape. This is a cave man version of centreless grinding! For the gauges use the intersecting chord theorem to set the teeth. If you can heat the steel the roughing can be done by hitting with hammers on a flat anvil, but the final accuracy is with polish and blue. The polish can be made from diamonds."

  8. #8
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    Quote Originally Posted by profloater View Post
    Steel is tough to work so you you need time but sand will wear it away with any rubbing block such as wood or cork. You make a gauge like a three tooth comb to define the radius, teeth make good points. Where the centre tooth touches you wear away. As accuracy improves use a “blue” made of grease and pigment, this can easily achieve 0.0001 inch accuracy. When a part is ready you can cast off a pattern using clay, this will speed up production but sanding will take a long time. The flat plate will help extend the rounded area along the length. But a straight edge would do. There is a risk of making constant diameters instead of circles but a series of three tooth gauges of different sizes help with that. Geometry knowledge will help make the gauges but you said absolute dimension is less critical than accuracy of shape. This is a cave man version of centreless grinding! For the gauges use the intersecting chord theorem to set the teeth. If you can heat the steel the roughing can be done by hitting with hammers on a flat anvil, but the final accuracy is with polish and blue. The polish can be made from diamonds. Does that work for you?
    My bold. I don't have the foggiest idea what that means. A picture would help.

  9. #9
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    Quote Originally Posted by roboticmhd View Post
    1. compass does, two pointy ends that keep at constant distance: can be made manually, allowed.
    2. hand drawn circle: allowed
    3. yes lump of steel is allowed, lot's of common abundant natural materials available, steel/iron lumps already smelted from ore.
    4. casting allowed as long as the pattern is not made using already accurate modern tools.

    extra:
    5. granite/ cast iron surface plate(s) already made
    Please tell us in appropriate detail what types of tools, from what era, you would accept for this exercise. Simple tools used in ancient times need not be considered inaccurate. We know that skilled craftsmen in classical Greek and Roman times could make accurately shaped columns from stone. The same techniques could in principle be used on steel, but the job would be excruciating slow because the metal wears very slowly when worked with abrasives.

  10. #10
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    Quote Originally Posted by Hornblower View Post
    My bold. I don't have the foggiest idea what that means. A picture would help.
    A UK 50 p coin is a constant diameter shape, a series of arcs centred on the outside edge in that case. Its diameter is constant but it’s not a circle. To correct if making, one needs a gauge the right size. Using the method I described it would be more accurate to say a constant radius shape but not truly centred, is a likely danger since the three point gauge does not know where the future centre will be. Smoothing that can make a constant diameter non circular shape. That assumes at some point you use a caliper as a diameter. Once your gauge finds the lobes of the incorrect shape, you risk just making it smaller without finding the true centre. One way to avoid this is to modify the gauge to have a centre mark, this needs a true square but that is easy to make.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  11. #11
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    Quote Originally Posted by profloater View Post
    A UK 50 p coin is a constant diameter shape, a series of arcs centred on the outside edge in that case. Its diameter is constant but it’s not a circle. To correct if making, one needs a gauge the right size. Using the method I described it would be more accurate to say a constant radius shape but not truly centred, is a likely danger since the three point gauge does not know where the future centre will be. Smoothing that can make a constant diameter non circular shape. That assumes at some point you use a caliper as a diameter. Once your gauge finds the lobes of the incorrect shape, you risk just making it smaller without finding the true centre. One way to avoid this is to modify the gauge to have a centre mark, this needs a true square but that is easy to make.
    I still cannot reconcile your words "constant diameter" and "not a circle." A picture would help.

  12. #12
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    Quote Originally Posted by Hornblower View Post
    I still cannot reconcile your words "constant diameter" and "not a circle." A picture would help.
    Jeremy-Fisher-2017-UK-50p-BU-3883-2.png

  13. #13
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    Quote Originally Posted by Darrell View Post
    Thanks.

  14. #14
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    Quote Originally Posted by Hornblower View Post
    Thanks.
    Did not have small change about me, sorry I did not find a picture.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  15. #15
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    Quote Originally Posted by Hornblower View Post
    Please tell us in appropriate detail what types of tools, from what era, you would accept for this exercise. Simple tools used in ancient times need not be considered inaccurate. We know that skilled craftsmen in classical Greek and Roman times could make accurately shaped columns from stone. The same techniques could in principle be used on steel, but the job would be excruciating slow because the metal wears very slowly when worked with abrasives.
    Addendum: Here are some links to the history of casting iron and steel in ancient times, and to some appropriate tools.

    http://www.metal-technologies.com/do...g.pdf?sfvrsn=8
    https://www.yashmachine.com/blog/his...ool-invention/

    The tools predate the casting of iron and steel, in some cases by many centuries. In principle a craftsman could turn a wooden cylindrical form, use it to make a mold, and then cast iron or steel into a rough cylinder. That piece of metal could be centered in the lathe to guide the craftsman in finding the high spots and grinding them down to an arbitrarily high level of precision with suitable grinding implements. The only thing missing in this era was modern tool steel for machining the work with modern techniques.

    For this thought exercise are you disallowing the ancient lathe and requiring the craftsman to limit himself to what a Stone Age cave man could have used on perhaps a meteorite?

  16. #16
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    Ask for a string and pencil, make a circular compass. Cut out a surface plate. Repeat as needed. Line 'em up.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  17. #17
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    A key restriction is whether you use modern knowledge. A lathe is not hard to make if you know the basics and you can use diamonds as cutters, like spending the longest time to sharpen the axe before cutting the tree, making the right tools could save time overall.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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