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Thread: Crucible dividers?

  1. Quote Originally Posted by Pat Barry View Post
    Hi Edwin, I must be missing out on how you would accomplish this quickly with a set of dividers. It seems like a lot of guess and check and reguess and recheck, etc, spiraling ever closer to the correct answer. This seems like it would take quite some time. I'd like to learn a better way. Can you walk me through your method to accomplish what you outlined as the problem above?
    You really need to take a look at the By Hand and Eye book. All is explained. And it's a lot easier and a lot more exact that you think.
    Fair winds and following seas,
    Jim Waldron

  2. Quote Originally Posted by Edwin Santos View Post
    Hi Pat,
    Here's how I would do it: First, I'd cut a story stick in length exactly the height of my case, in this example 31" but in a moment you'll see it can be anything. If the case exists, then I would make the stick with no measuring by holding the stick up to the case, marking the line and cutting. Then take a piece of the 3/4" material from the outside case and holding it, mark off that thickness at each end of the stick. This now gives us the interior space of the carcase between the two lines we just marked.

    I would then take my dividers and open them up to a rough estimate of one sixth of the case by eye. Very rough. Now walk the dividers in between the two lines you made, adjust, do it again until six steps lands you precisely on the line at the other end of the stick. Yes, this is trial and error, but you shouldn't have to do more than two or three iterations, because when you adjust the dividers bigger or smaller a tiny bit it makes a big difference because the change accumulates sixfold, once for each step. Now our dividers are representing exactly 1/6 of the interior case center line to center line. Walk them one last time, pushing in the point at each step to mark the division lines, and then come back with your pencil to mark them. This entire process shouldn't take more than about 10 minutes honestly.
    So what if we want to subtract out the interior partitions and illustrate the sub spaces inside the case? In the example, I said the interior partitions were 15/32" material. Take a scrap piece of that material and adjust/set the dividers to half the thickness using the walking method. Then place the dividers on each partition center line and walk once above and below that line to then mark the partition thickness. Now your story stick is a complete vertical representation of the case showing the top, bottom, each partition, and each space in between all of which which should be identical. Transfer all measurements from this stick in the course of building your piece including the drawers (height and width at least), and then label and keep it if you ever intend to build the item again. In this process you have not needed nor reached for a tape measure or ruler.

    I hope this makes sense. It's one of those things that's easier to show than explain in words. Often I end up tacking a temporary hook to the end of a horizontal story stick and using it for setting up crosscutting stop blocks on the table saw sled. This is how I was taught, and if there's a better way than the method I've described, please someone let me know.

    If the eye method of getting in the ballpark with the dividers sounds too rough, there are two other methods that give you a starting point that will be very close, I can share if interested.
    Edwin
    That's making your point the hard (and slow) way. Line off your opening, as you said. Walk off the number of divisions you want with a guesstimate of the proper length. When it comes out over or under, divide (by eyeball) the "overage" or "underage" into the same number of equal divisions you're looking for (six, in your example). Then, set your dividers to the original interval plus (or minus in the case of "underage") one sixth of the "overage" amount and you should be virtually dead on. Quick as a bunny and the only source of error is your sloppiness in execution. If it's off by much, you can repeat the process from the new dimensions and be a bit more careful and you're there. Not ten minutes at all. More like two or three if you're careful and accurate the first time through and come out with a good result the first time.
    Fair winds and following seas,
    Jim Waldron

  3. #93
    Well I was only trying to answer his question. Sorry if I belabored it.

  4. #94
    Quote Originally Posted by Edwin Santos View Post
    Hi Pat, .
    So what if we want to subtract out the interior partitions and illustrate the sub spaces inside the case? In the example, I said the interior partitions were 15/32" material. Take a scrap piece of that material and adjust/set the dividers to half the thickness using the walking method. Then place the dividers on each partition center line and walk once above and below that line to then mark the partition thickness. Now your story stick is a complete vertical representation of the case showing the top, bottom, each partition, and each space in between all of which which should be identical.
    Edwin
    Won't the top and bottom space be larger than the intervening ones by the amount of your divider?

  5. #95
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    Quote Originally Posted by bridger berdel View Post
    Won't the top and bottom space be larger than the intervening ones by the amount of your divider?
    Indeed they will. This is what we software types refer to as a "fencepost error". It happens more often than anybody likes to admit :-)

  6. #96
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    I would approach the above problem this way: If the height is 31 then on a stick say 36, I would come in from the end a couple inches and strike a line and mark TOP on the portion beyond the mark. Then measure 31 and strike then mark BOT on the wild end. Gauge a line end to end on the story stick, it is in that line where the stepping takes place. Assuming shelves, top and bottom panels are equal thickness, gauge the top and bottom panels and strike marks. Now use the dividers to step out even margin from top of top panel to top of bottom panel. Here is where I think the Crucible Divider is at the disadvantage since it lacks a screw feed spreading mechanism, with a spring loaded screw hair width accuracy is under control. Once the upper surfaces have been gauged and marked, layout the undersides stepping from bottom of the bottom panel to the bottom of the top panel with the dividers unchanged. Everything should work out evenly without odd remainders or centering problems.

  7. #97
    Quote Originally Posted by Patrick Chase View Post
    Indeed they will. This is what we software types refer to as a "fencepost error". It happens more often than anybody likes to admit :-)
    Man, I've done that more than once. Didn't know it was common, nor that it was a mathematical oddity studied by some big brained Roman scholar. I just figured I was a dope [don't say it!], erased the lines and started over.

    Interesting factoid Patrick. How the devil do you find - and remember - this stuff, anyway?

  8. #98
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    Quote Originally Posted by Edwin Santos View Post
    Hi Pat,
    Here's how I would do it: First, I'd cut a story stick in length exactly the height of my case, in this example 31" but in a moment you'll see it can be anything. If the case exists, then I would make the stick with no measuring by holding the stick up to the case, marking the line and cutting. Then take a piece of the 3/4" material from the outside case and holding it, mark off that thickness at each end of the stick. This now gives us the interior space of the carcase between the two lines we just marked.

    I would then take my dividers and open them up to a rough estimate of one sixth of the case by eye. Very rough. Now walk the dividers in between the two lines you made, adjust, do it again until six steps lands you precisely on the line at the other end of the stick. Yes, this is trial and error, but you shouldn't have to do more than two or three iterations, because when you adjust the dividers bigger or smaller a tiny bit it makes a big difference because the change accumulates sixfold, once for each step. Now our dividers are representing exactly 1/6 of the interior case center line to center line. Walk them one last time, pushing in the point at each step to mark the division lines, and then come back with your pencil to mark them. This entire process shouldn't take more than about 10 minutes honestly.
    So what if we want to subtract out the interior partitions and illustrate the sub spaces inside the case? In the example, I said the interior partitions were 15/32" material. Take a scrap piece of that material and adjust/set the dividers to half the thickness using the walking method. Then place the dividers on each partition center line and walk once above and below that line to then mark the partition thickness. Now your story stick is a complete vertical representation of the case showing the top, bottom, each partition, and each space in between all of which which should be identical. Transfer all measurements from this stick in the course of building your piece including the drawers (height and width at least), and then label and keep it if you ever intend to build the item again. In this process you have not needed nor reached for a tape measure or ruler.

    I hope this makes sense. It's one of those things that's easier to show than explain in words. Often I end up tacking a temporary hook to the end of a horizontal story stick and using it for setting up crosscutting stop blocks on the table saw sled. This is how I was taught, and if there's a better way than the method I've described, please someone let me know.

    If the eye method of getting in the ballpark with the dividers sounds too rough, there are two other methods that give you a starting point that will be very close, I can share if interested.
    Edwin
    Thanks Edwin. This is pretty much what I expected and how I would do it also. I guess I'm stuck in the age of calculators and rulers though. Whatever works for you I guess.

  9. #99
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    Quote Originally Posted by James Waldron View Post
    You really need to take a look at the By Hand and Eye book. All is explained. And it's a lot easier and a lot more exact that you think.
    Yes - Edwin explained it just about like I imagined it. If I were stuck without a tape measure I'd probably do it the same way.

  10. #100
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    Quote Originally Posted by Patrick Chase View Post
    Indeed they will. This is what we software types refer to as a "fencepost error". It happens more often than anybody likes to admit :-)
    Ah, once again you are correct Patrick (and bridger of course). That throws a bit of a problem into the method. The centerlines for the drawer dividers will be equidistant but the openings for the drawers won't be the same size top and bottom versus the ones in the center.

  11. #101
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    Pat Barry, read my post #96, it presents a solution to the post problem.

  12. #102
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    Here is a link to a name-brand example. There are cheaper versions of the first that work very well.

    http://www.starrett.com/metrology/product-detail/metrology/metrology-products/precision-measuring-tools/calipers-dividers-trammels/calipers-dividers/73B-6

    The quick-spring nut feature speeds adjustment up.

    The Starrett 92 pictured below is my favorite because it is an impressive tool and also works as a compass, but I admit it is not quite as rigid as the first version.


    Stan
    Last edited by Stanley Covington; 09-12-2017 at 9:16 AM.

  13. #103
    Quote Originally Posted by Patrick Chase View Post
    Indeed they will. This is what we software types refer to as a "fencepost error". It happens more often than anybody likes to admit :-)
    Quote Originally Posted by bridger berdel View Post
    Won't the top and bottom space be larger than the intervening ones by the amount of your divider?
    Your are correct on this oversight sirs. Roger's method above corrects for the "fencepost error".

  14. #104
    Stanley, that is indeed a great dividers/ compass combination from Starrett. They are not really any cheaper than the Crucible ones, but the utility is better. Last year at the Brimfield flea market in central Mass., I found the identical vintage Stanley version of the above dividers/compass for about $40.00, so that was my "find" for the summer. I leave that tool in the compass configuration, as it is not quite as easily handled as dedicated dividers.

  15. #105
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    Quote Originally Posted by Frederick Skelly View Post
    Man, I've done that more than once. Didn't know it was common, nor that it was a mathematical oddity studied by some big brained Roman scholar. I just figured I was a dope [don't say it!], erased the lines and started over.

    Interesting factoid Patrick. How the devil do you find - and remember - this stuff, anyway?
    I think I read it in a software journal or something like that. I remember knowing about it when one of my fencepost bugs screwed up a finite element simulation for laser media in the mid 80s (my Dad allowed me to choose between helping with his simulation or digging ditches for the sprinkler system during the summer), so it's been at least that long. I have no idea why my neurons retain that and not useful stuff.

    Also I've interviewed a lot of software candidates, and one of my favorite questions while at a previous employer was a bit of a "fencepost trap", i.e. it tricked the candidate into making that mistake unless they were really careful.
    Last edited by Patrick Chase; 09-12-2017 at 3:38 PM.

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