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Thread: Ancient Tools - The Stringline

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    Ancient Tools - The Stringline

    karuko1.jpg



    The stringline is simply a string. Sometimes it is called a dryline because chalk or ink are not applied, and it does not leave a mark. The humble stringline has been an important tool in construction and woodworking long before Himiunu was pacing off Cheops' resurrection pile.

    Do you own a really precise steel straightedge a meter or yard long? Most woodworkers don't. They are horribly expensive, a pain to store and haul around, and don't tend to stay straight. But in the horizontal direction, a taught stringline is perfectly straight over its entire distance, be that 1 yard or 100 yards. Think about it. I hope you can see the power of this inexpensive tool.

    One common and ancient application of the stringline is to check the straightness of a board, wall, concrete form, doorframe, cabinet carcass, etc.. For this you need a good stringline, hooks or pins, and three small blocks of wood perhaps 1/2" square and 2" long. Hooks can be made from wire, pins can be made from nails, and you already know how to make the small blocks of wood. I use 2 of the plastic widgets in the attached picture which combines pins (for pushing into wood) and a hook into a single tool with a cap. They can also be secured with a nail.

    To use the stringline, hook, pin, or nail one end on the board, wall, concrete formwork, doorframe, floor, ceiling, cabinet carcase, etc. to be checked (the "Thing"). Stretch the stringline very tight, and hook/pin/nail the stringline to the opposite edge of the Thing. Insert one of the blocks of wood you prepared under the stringline at each end. The stringline is now stretched more-or-less 1/2" away from the Thing's surface. Now, place your third block of wood between the stringline and Thing's surface, and move it the length of the stringline. Wherever the block lightly kisses the stringline without making it deflect, the surface is "in line" with both of its ends. Where there is a gap, the surface has a depression or "swamp" relative to its ends. Where the traveling block makes the string bow out, the surface has a "belly." Use a pencil, lumber crayon, or chalk to mark the swamps with a circle, and the bellys with a + mark.

    Note there are limits to the accuracy of this method when the string is stretched over the top of or underneath a Thing because gravity makes it sag in the middle. The longer the distance, the greater the sag. It can be reduced by stretching the stringline tighter. But you can easily account for the sag if you pay attention.

    I don't layout buildings or walls anymore, but I find myself using a stringline frequently when conducting quality inspections of jobsites and factory inspections of construction materials and assemblies. In many cases, it is the only tool for the job.

    More times than I can count I have asked a contractor on the jobsite if his stud/gypboard walls, concrete forms/walls, block walls, or ceilings are straight. "Yassir," he always says, "straight as a frikin arrow." He'll pull out a 1-meter straightedge, press it against the surface, and say "See?" It looks pretty good, dagnabit. Then I stretch my stringline, fiddle with my blocks and pencil, and show him the truth. I take pictures, and leave the stringline in place so he and his layout crew, framing crew, drywall crew, and their QC dude, can check for themselves. More frequently than I like, I have to show them how its done. Embarrassing for them, but its my yob. I usually need to do this only two or three times before the contractor gets the hint and starts making his walls/ceilings straight, but if his work product is still sub-standard, I make him tear it out and redo. Ouch.

    A similar situation occurs regularly when I inspect curtainwall frames (sash) or tall doorframes, especially stainless steel doors and doorframes. These expensive products have specified tolerances. During an inspection at the jobsite or factory, the manufacturer and installer always respond to my polite questions about tolerances with "Yassir, straight as frikin arrow," and with great dignity press their $20 scratched and dinged straightedge against the beautifully polished stainless steel surface while they smile at me indulgently as if I was a small schoolboy with a snot bubble coming out my nose. But 6 times out of 10, my unpretentious stringline and little blocks of wood, combined with feeler gauges, send them beetling away in a panic to find their QC dude.

    This ancient tools works well in the woodshop too when you need to check for the flatness of a board or tabletop or workbench, or the alignment of cabinet frames.

    Another common but more elegant application is testing for wind or flatness. Let's say, for example, that you need to install an h84" x w72" double door frame in a wall. Do you own 2 ten foot straightedges or winding sticks to check for twist in the assembly? How would you even using winding sticks on a doorframe in a wall? This job has been handled by stringlines forever, and the technique has applications everywhere in woodworking and construction. Sadly, most craftsmen settle for using a spirit level nowadays, and the resulting quality is quite poor.

    First, plane the sides and top of the doorframe's edges straight and square. Your stringline, used as in the example above, can help with this. Then assemble the doorframe with all 3 members square and properly aligned. Then mount one side in the opening, plumb it in both axis (a plumbline is better, but I will save plumblines for another post in this series about ancient tools), and tack it into place. I assume you know how to use wedge shims to ensure it is installed straight without bending, bowing, or "doing the wave."

    You need to have a temporary spreader board attached between the two uprights to keep the bottom of the doorframe opening the precise width.

    Second, pin one end of your stringline at one corner, pull it across the opening (not too taut), and pin it to the diagonal corner. Let's call this the "inside string." Now pin a stringline across the other diagonal. Let's call this the "outside string." The two diagonals form an "X" which is a name given to this technique. Wrap the same stringline 5 to 8 times around each end of the outside string where it rides over the frame's corners. The string must be wrapped very neatly so there is only one layer of string between it and the wood. No doubling up. This wrapping will elevate the outside string precisely the thickness of the string away from the inside string when the doorframe's edges are in plane. A slicker and quicker method is to make two shims the same thickness as the string and slip them under the outside string's ends instead of wrapping with string.

    Now, adjust the position of the unmounted vertical doorframe member so the two strings just kiss and bounce, and then kiss and bounce. If you paid attention, the doorframe is now in a single plane and free of twist. Check the doorframe during and after installation to make sure it stays free of wind.

    Do you have a workbench top or tabletop or countertop or large cabinet assembly that you need to make flat and free of wind, but is too big for your straightedges or winding sticks? Give this technique a try. It never fails. Combine it with wooden blocks and a pencil, and you will be master of all you survey.

    The precision of this tool is improved in manufacturing by using thin, kink-free steel wires stretched tightly and given an electrical charge. When the two wires touch, a circuit is closed and a light goes on or a buzzer sounds.

    A stringline must be a balance of thin and strong. A good stringline will be tightly wound, with a smooth-ish surface, versus being corrugated like a manila-rope hawser, and not hairy with frayed threads. A fuzzy stringline is absolutely useless for this job. I have never seen a usable stringline being sold at a big-box home center, BTW. The old woven nylon fishing lines were pretty good. Good stringlines can still be found in Japan.

    A bright flashlight can be useful in seeing swamps, bellys, and stringline contact.

    The world's best craftsmen have used stringlines for thousands of years. Give it a try.

    Please add your experiences and techniques to this thread.

    Stan
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    Last edited by Stanley Covington; 09-27-2017 at 12:09 AM.

  2. #2
    No experiences to add - just wanted to say thanks for another excellent lesson!
    Fred

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    Quote Originally Posted by Frederick Skelly View Post
    No experiences to add - just wanted to say thanks for another excellent lesson!
    Fred
    You are welcome, Fred. Sorry it is sooo long.

    Stan

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    This is my quick easy and cheap board evaluation set up.
    Jim
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    Stan, your method of hanging doors is exactly how I've done it, except for the wrap around the second string. I usually just hold the second string and bring it to the frame while watching the point where the two meet. Your method is definitely more accurate! I use a spacer at the bottom too, never knew anyone else did that!

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    Quote Originally Posted by Jeff Bartley View Post
    Stan, your method of hanging doors is exactly how I've done it, except for the wrap around the second string. I usually just hold the second string and bring it to the frame while watching the point where the two meet. Your method is definitely more accurate! I use a spacer at the bottom too, never knew anyone else did that!
    I see you have a classical education! When I was a green-as-grass apprentice, I was helper to a old retrobate in his 70's who specialized in doorframes and doors. Las Vegas hotels have a lot of doors, mostly heavy steel. The pressure to install 5 doors/frames per hour (including hinges but not knobs, closures, peepholes etc.) was high, but he never slacked on straight, square, and twist. We used these techniques on over a thousand doors during the time I worked with him.

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    Quote Originally Posted by James Pallas View Post
    This is my quick easy and cheap board evaluation set up.
    Jim
    Thanks, Jim. I like the plumbob/line/chalkbox combination!

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    The string line! A wonderful post Stan. My father is a metal fabricator and these are some of his preferred methods for checking, a very handy tool indeed!
    Bumbling forward into the unknown.

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    Quote Originally Posted by Stanley Covington View Post
    You are welcome, Fred. Sorry it is sooo long.

    Stan
    For what it is worth, posts like this are why I joined SMC. I don't need another sharpening thread with nine pages of debate about how many angels can dance on the head of a pin.

    Stuff like this, feel free to make it as long as you want.

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    Tip hat to Master Covington...

    Thanks for the informative post.

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    Used a stringline every day as a concrete form carpenter......Helped when straightening long wall forms....also help when straightening a stick-built wall. Used both a Red Chalk line, and a blue chalk line.....and a 100' straight line reel. Needed to layout a radius for a parking curb? Stake at one end, measure out to the length of the radius, and mark as you walked along with a spray can of paint. Then bend the forms to match.

    One thing...string lines need to be pulled tight as you can get them. Lines tend to sag otherwise. Almost an art form, when it comes to tying off a line. There is a special knot to use....
    Last edited by steven c newman; 09-26-2017 at 11:33 AM.

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    Excellent lesson as always Stan. I do have to nit-pick one teeny tiny point:

    Quote Originally Posted by Stanley Covington View Post
    Do you own a really precise steel straightedge a meter or yard long? Most woodworkers don't. They are horribly expensive, a pain to store and haul around, and don't tend to stay straight.
    You were OK right to to "don't tend to stay straight". My Starrett 385-48 was stupidly expensive (it cost more than many "premium" handplanes!), and is a pain to store and haul around, particularly when you consider the importance of preserving my investment. It and similar straight edges are however stable as a rock. I've seen very old ones that are still good to within microns, provided they weren't abused.

    Straight edges and stringlines are really different tools for different purposes. The straightedge is expensive, inconvenient, and short but is accurate to within 0.8 mils (~20 microns) over 4 feet. The stringline is small, portable, cheap, and much longer, but has much higher uncertainty. The braiding of the stirng alone adds more imprecision to any given point than the straightedge accumulates over its entire length, but for most purposes we simply don't care, and the stringline is therefore the more appropriate tool.
    Last edited by Patrick Chase; 09-26-2017 at 11:48 AM.

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    Quote Originally Posted by steven c newman View Post
    Used a stringline every day as a concrete form carpenter......Helped when straightening long wall forms....also help when straightening a stick-built wall. Used both a Red Chalk line, and a blue chalk line.....and a 100' straight line reel. Needed to layout a radius for a parking curb? Stake at one end, measure out to the length of the radius, and mark as you walked along with a spray can of paint. Then bend the forms to match.

    One thing...string lines need to be pulled tight as you can get them. Lines tend to sag otherwise. Almost an art form, when it comes to tying off a line. There is a special knot to use....
    A perfect set of examples, Steve. Thank you. I think I know the knot you mentioned, but please favor us with a description if you would.

    Stan

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    Quote Originally Posted by Patrick Chase View Post
    Excellent lesson as always Stan. I do have to nit-pick one teeny tiny point:



    You were OK right to to "don't tend to stay straight". My Starrett 385-48 was stupidly expensive, and is a pain to store and haul around (particularly when you consider the importance of preserving my investment), but it and similar straight edges are stable as a rock. I've seen very old ones that are still good to within microns, provided they weren't abused.

    Straight edges and stringlines are really different tools for different purposes. The straightedge is expensive, inconvenient, and short but is accurate to within 0.8 mils (~20 microns) over 4 feet. The stringline is small, portable, cheap, and much longer, but has much higher uncertainty. The braiding of the stirng alone adds more imprecision to any given point than the straightedge accumulates over its entire length, but for most purposes we simply don't care, and the stringline is therefore the more appropriate tool.
    I must respectfully disagree with you about the stability of even expensive straightedges, especially if they are used outside of temperature-controlled environments, or spend time in a pickup truck's toolbox. And how many concrete walls will it take to degrade mils of accuracy?

    I agree with your point about braiding, but this thread is not about precision tools, or tolerances less than can be judged by Mark-1 Eyeball.

    I can almost see those tiny winged angels dancing away... is it the samba? Or maybe the merengue? https://www.youtube.com/watch?v=UtTB7gfnEgs
    Last edited by Stanley Covington; 09-26-2017 at 12:02 PM.

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    Make a loop around a finger...spin the loop about 10 turns...slip the loop over the pin/nail/stake. Pull as tightly as you can. wrap the rest of the line around the loop in a figure 8 fashion. Line will stay tight, yet release when needed...takes about 30 seconds to tie.

    Hook end went under a square of 3/4" plywood scrap. Nail that to one end of the top plate of a wall. go to the other end of the wall, pull line tight and add to another such block. Use a ladder and a third block to straighten the wall. Block to check the "gap", turnbuckle braces to adjust in or out.

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