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DIY 5" sine bar

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  • #31
    For what its worth:

    sin 5 degrees = 0.0872

    and similarly is:

    Tan 5 degrees = 0.0875

    The difference over 5 units is (0.0875 - 0.08720) = 0.0003 units over 5" length so the difference is minute (very small) and nothing to get hung up about.

    A good scientific/mathematical calculator will do the conversion from decimal degrees to degrees:minutes:seconds - and reverse - with just one or perhaps two keystrokes.

    The difference over either the sin or tan of an angle is very close to being linear over a distance 5 degrees

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    • #32
      OldTiffie THANK YOU. I have never been able to understand why some individuals on these various forums need to slag others off for presenting ideas, esp ones that seem to be well documented.

      So, I appreciate greatly that you and the others above took the time to find the information for me/us and share it. I enjoy making tools to use for my various projects. I promise not to use over specified dimensions, I am happy when two parts fit close-enough for the purpose :-)

      Gerrit

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      • #33
        Wish I could see pictures

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        • #34
          Yes, for small angles there is very little difference between the sine and the tangent functions. But as the angle gets larger, the difference increases at an accelerating rate. The sine of 45 degrees is 0.7071 while the tangent is 1.000. And when you get to 90 degrees the sine is 1.000 while the tangent is infinite. You just can't get a bigger difference than that.

          So don't try to expand that trick as you will quickly get into trouble.

          I took similar liberties in the case of small angles in my article that I posted a link to above.



          Originally posted by oldtiffie View Post
          For what its worth:

          sin 5 degrees = 0.0872

          and similarly is:

          Tan 5 degrees = 0.0875

          The difference over 5 units is (0.0875 - 0.08720) = 0.0003 units over 5" length so the difference is minute (very small) and nothing to get hung up about.

          A good scientific/mathematical calculator will do the conversion from decimal degrees to degrees:minutes:seconds - and reverse - with just one or perhaps two keystrokes.

          The difference over either the sin or tan of an angle is very close to being linear over a distance 5 degrees
          Paul A.
          SE Texas

          And if you look REAL close at an analog signal,
          You will find that it has discrete steps.

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          • #35
            Thanks Gerrit - appreciated.

            A very obvious and practical and useful "angle setter/measurer" is the common shop rotary table. I got rid of my very good 8" rotary table as my 6" rotary tables do all that I need - the 8" table was far too heavy and awkward for me and it was just an accident waiting to happen - so "Zip" - it got "binned" to/for scrap as it had no value to me and it just took up space that could be better used for other "stuff".

            Stand it vertical (on its end), bolt an angle plate to the face of it with the vernier setting to zero and the "flat" (face) of the angle plate set to zero (horizontal) - and there you have an ability to measure and/or set up to an angle of 20 arc minutes which is more than accurate enough for may purposes.

            The angles do not need to be calculated and they can be read off and be set or read directly from the hand-wheel and table vernier.

            A magnetic angle table is a great help too - especially on a surface grinder or tool and cutter grinder. There may be no need to bold the rotary table to a machine table either as both work quite well enough on any reasonably flat surface (including but not necessarily needed - a surface plate).

            The rotary table is not as "stiff/rigid" as I'd like when it is stood vertically on a machine table so I used a bit of hot rolled 1" x 1" x 1/8" angle - seen here - works a treat and was made from stuff I had in the shop and cost no money or very little time.

            Last edited by oldtiffie; 10-06-2016, 10:22 PM.

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            • #36
              Smaller compound angles - easy:



              A tilting table on a rotary table takes care of a lot of the more "difficult" "compound" angles as well.



              And these variations to a theme i.e. setting/reading angles etc.).



              Last edited by oldtiffie; 10-07-2016, 03:05 AM.

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              • #37
                Originally posted by oldtiffie View Post
                (snip)

                One of these days I will start a thread about "limits and fits" and "tolerances" and "surface finish" all of which are inter-related/dependent/reliant to some degree - and how to take advantage of them for the optimum result.
                At first reading, I wondered, why bother? Pretty much all is covered in even my oldest Handbook.
                But the forum brings interesting response and experience.
                In my no doubt limited definition of "Home shop machinist" a true grasp of tolerance seems lacking. An individual who can produce flawless parts on their own can be at a complete loss if having to spec' for a jobber whereas the jobber can likely move decimals to the left and produce functional cost efficient parts.

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                • #38
                  And a few more: "angle setting/measuring":



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