Page 4 of 7 FirstFirst 1234567 LastLast
Results 46 to 60 of 100

Thread: Ancient Tools - Divider & Compass

  1. #46
    Join Date
    Aug 2012
    Location
    Missouri
    Posts
    2,151
    Quote Originally Posted by steven c newman View Post
    Maybe start a "build thread" about how to make one? I'm sure someone here can do that? I'll look around this weekend, and see what metal I can scrounge up. maybe some Brass knobs to dress it up a bit? Quandrant might be just a plain flat piece, have a brass knob to lock it in place? Hmmmm....
    Steven from the work you have shown you are more than capable of making dividers. Two points and a way to hold the setting is about it. I'll be watching to see what you come up with.
    Jim

  2. #47
    Join Date
    Dec 2016
    Location
    South West Ontario
    Posts
    1,502
    I remember a year of drafting classes many years ago, before they let us loose on machines or tools. I also remember how boring it was, the equipment was rather good however. I blame the teacher as good teachers left their mark on their subject.
    As the need arises we learn things and methods, often the simple things prove most useful and more accurate. I love 'clever' ways of working. Story sticks, patterns and jigs improve my accuracy and productivity, I work to a ruler on a large scale more than small scale.
    I will look for a large pair of dividers to expand my range.

  3. #48
    Join Date
    Dec 2015
    Location
    Dublin, CA
    Posts
    4,119
    Quote Originally Posted by Pat Barry View Post
    Yes, you can see a hair. I don't think you could see a spread of .003" between points of a divider. Let's face it, the points aren't .001" diameter.
    Let's use Warren's example to look at what sorts of errors you can accumulate with a tape measure. Turned finials typically have always-varying diameter (i.e. there are no significant cylindrical sections), so the obvious gotcha is that your tape will always be trying to "walk" in one direction or the other as it wraps around the piece, causing the effective circumference to change. I don't know about you, but I don't find it very easy to keep a tape perfectly perpendicular to the piece's long axis under those conditions. In contrast it's pretty easy to mark a circumference on the piece while turning, and use that to guide your dividers as you walk them around.

    I would guess that the dividers' accuracy advantage would be measured in hundredths rather than mils in that case. Warren picked that example for a reason.
    Last edited by Patrick Chase; 09-13-2017 at 1:52 AM.

  4. #49
    An accurate tape - Lufkin W606P - only 1/4" wide and 6 feet long - we have a dozen or so and use them everyday in out shop - no clip error as there is no clip as zero is 3 inches from the end - no burning an inch which eliminates many errors. Backside reads diameter when wrapped around. Dimensions on tape are precise. Fits nicely in pocket.

  5. #50
    Join Date
    Sep 2007
    Location
    Longview WA
    Posts
    27,347
    Blog Entries
    1
    Quote Originally Posted by James Pallas View Post
    Those look very nicely done Jim. I've never used any. Thought about making or buying them. What ratios did you use to make them?
    Jim
    Mine were made using a pattern found online:

    Fibonacci Gauge.png

    The rivets came from Lee Valley:

    http://www.leevalley.com/us/hardware...=3,41306,41327

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  6. #51
    Join Date
    Dec 2015
    Location
    Dublin, CA
    Posts
    4,119

    Post

    Quote Originally Posted by Jim Koepke View Post
    Mine were made using a pattern found online:

    Fibonacci Gauge.png

    The rivets came from Lee Valley:

    http://www.leevalley.com/us/hardware...=3,41306,41327

    jtk
    The other lengths are really easy to derive from the length of the two long legs.

    • Let the length of the long legs be called 'AF' (AF = 340 mm in yours example)
    • In your drawing the length BG must be AF/golden_ratio = AF/1.62. (so BG = 340/1.62 = 210 mm in your example)
    • For the linkage to work the polygon ABEC must be a Rhombus. That tells us a couple things:
      • BF = BG (from rhombus angle equalities)
      • AB = BE = EC = CA = AF - BF = AF - BG (340 - 210 = 130 mm in your example)

    From that alone we have all of the dimensions. Note that you can create a divider for any ratio you want by replacing the number "1.62" in the second step.
    Last edited by Patrick Chase; 09-13-2017 at 6:00 AM.

  7. #52
    Join Date
    Apr 2010
    Location
    Tokyo, Japan
    Posts
    1,550
    Here is a link to an interesting website with instructions and pictures for basic techniques using dividers and compass. His precision could be better, but the technique is solid.

    http://toolbytool.com/ch07-compassDi...aightedge.html

  8. #53
    In addition to dividers and compass, we use so-called 10 point (actually 11 points and 10 spaces) and both standard and universal proportional dividers in the shop. The 10 points are available in larger sizes, which reduces the stepwise accumulation of errors, but I've never see a set of universals ( outside one of those 4' long mocked-up teaching aids) in anything other than 10", so will require a step or two with a standard divider for large projects (e.g., a hendecagon...11-sided table)...as Warren suggested, a little math and trial and error is usually faster where direct layout is not possible. We have a smaller set of proportionals for really small stuff like laying out string nuts or bridges. Available on eBay, although use caution as prices fluctuate wildly for quality drafting and layout tools. My dividers come mostly from a student formerly employed as a government map maker...lovely stuff tossed as useless as the job moved to digital media.

    Even if not using dividers for open shape layouts, they are handy for checking the final result.

  9. #54
    Join Date
    Aug 2010
    Location
    USA
    Posts
    5,582
    Quote Originally Posted by Patrick Chase View Post
    The other lengths are really easy to derive from the length of the two long legs.

    • Let the length of the long legs be called 'AF' (AF = 340 mm in yours example)
    • In your drawing the length BG must be AF/golden_ratio = AF/1.62. (so BG = 340/1.62 = 210 mm in your example)
    • For the linkage to work the polygon ABEC must be a Rhombus. That tells us a couple things:
      • BF = BG (from rhombus angle equalities)
      • AB = BE = EC = CA = AF - BF = AF - BG (340 - 210 = 130 mm in your example)


    From that alone we have all of the dimensions. Note that you can create a divider for any ratio you want by replacing the number "1.62" in the second step.
    Of course, you will need to MEASURE precisely to the specified dimensions in order to create a tool that performs as expected.

  10. #55
    Join Date
    Aug 2013
    Location
    Princeton, NJ
    Posts
    7,254
    Blog Entries
    7
    Quote Originally Posted by Warren Mickley View Post
    Maybe more accurate than trying to measure a very thin shaving with a micrometer. They used to teach this stuff in school.
    Hah!

    Thank you Stan! Great thread! Thank you Warren also, wonderful insights.

    I use dividers a fair bit, not as often as I should but good habits take time. I use them for shoji just as Stan mentioned in the previous thread.

    Tape measures are not especially accurate, mostly due to the moveable end piece, but they can repeat fairly well. I use mine for rough cutting stock and for measuring corner to corner to check squareness.

    We had a tape measure at the machine shop, and truly I can't recall it being used for anything other than building a crate to ship a finished motor. Even in scenarios where it may have been practical to use one we would usually default to a steel rule. I recall my mentor being appalled by the thought of using a tape measure for anything really, anytime I use one in my shop I can feel the same hairy eyeball I would receive if I were reaching for it in the machine shop, as if he is looking in on me and shaking his head.
    Last edited by Brian Holcombe; 09-13-2017 at 9:33 AM.
    Bumbling forward into the unknown.

  11. #56
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    836
    Quote Originally Posted by Pat Barry View Post
    Of course, you will need to MEASURE precisely to the specified dimensions in order to create a tool that performs as expected.
    It can be done without measuring anything. A compass and straightedge can be used to construct a Golden Rectangle and the appropriate dimensions transferred from there with dividers.
    Golden Rectiangle.jpg
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  12. #57
    Join Date
    Aug 2012
    Location
    Missouri
    Posts
    2,151
    To me the most important thing in measuring is portability. We use it all of the time. Marking gauges, calipers, set up blocks,etc, etc. Rulers and tapes do the same except for the fact that the human element comes into play, our eyesight, memory, steadiness of hand and such. Dividers do double duty by dividing and transferring. We even make things to make rulers and tapes better, ruler stops and all kinds of fancy rulers with preset markings. Dividers are a good part of the kit.
    Jim

  13. #58
    Join Date
    Aug 2010
    Location
    USA
    Posts
    5,582
    Quote Originally Posted by David L Morse View Post
    It can be done without measuring anything. A compass and straightedge can be used to construct a Golden Rectangle and the appropriate dimensions transferred from there with dividers.
    Golden Rectiangle.jpg
    Yes, I see that you can use the divider to construct golden ratio / rectangle.

    I'm not so sure that it can be used to create the dimension Patrick indicated (210 mm) from the 340 mm starting point however per Patrick: "the length BG must be AF/golden_ratio = AF/1.62. (so BG = 340/1.62 = 210 mm in your example)"

  14. #59
    Join Date
    Aug 2010
    Location
    USA
    Posts
    5,582
    Quote Originally Posted by Brian Holcombe View Post
    Hah!

    Thank you Stan! Great thread! Thank you Warren also, wonderful insights.

    I use dividers a fair bit, not as often as I should but good habits take time. I use them for shoji just as Stan mentioned in the previous thread.

    Tape measures are not especially accurate, mostly due to the moveable end piece, but they can repeat fairly well. I use mine for rough cutting stock and for measuring corner to corner to check squareness.

    We had a tape measure at the machine shop, and truly I can't recall it being used for anything other than building a crate to ship a finished motor. Even in scenarios where it may have been practical to use one we would usually default to a steel rule. I recall my mentor being appalled by the thought of using a tape measure for anything really, anytime I use one in my shop I can feel the same hairy eyeball I would receive if I were reaching for it in the machine shop, as if he is looking in on me and shaking his head.
    Yes - I agree - you won't find much use for a tape measure in a machine shop. You will however find many more uses in a sheet metal shop.

  15. #60
    Join Date
    Sep 2007
    Location
    Longview WA
    Posts
    27,347
    Blog Entries
    1
    Quote Originally Posted by Pat Barry View Post
    Of course, you will need to MEASURE precisely to the specified dimensions in order to create a tool that performs as expected.
    Mine were laid out using a metric zig-zag rule and 'burning' the first centimeter.

    Also the points weren't cut until after assembly.

    jtk
    Last edited by Jim Koepke; 09-13-2017 at 12:41 PM. Reason: Also the points weren't cut...
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •