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Thread: Thinking out loud...... Thermodymics vs woodworking precision measurement tools?

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  1. #1
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    Thinking out loud...... Thermodymics vs woodworking precision measurement tools?

    OK, I am sitting in my garage consuming an adult beverage and looking at a TSO MTR-18 Triangle. It's 89* don't know the humidity.

    My garage is heated, but not air conditioned.

    My question. How does change in outdoor temperatures affect the accuracy of these types of tools (i.e. Starret (sp), Woodpecker's, TSO, et al measuring devices)?

    I am also interested in reading the extent woodworkers go to achieve machine accuracy...

    Temperature affects metal. how do we protect our high dollar measuring instruments? OR should we just buy a good quality framing square, bone up on our high school trig?k

    Hoping for some fun and interesting commentary...
    Last edited by Joe Mioux; 07-14-2021 at 7:26 PM. Reason: THERMODYNAMICS
    Vortex! What Vortex?

  2. #2
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    Outdoor temp has no effect on the stuff inside. In metal working you use gloves to handle the measuring instruments so body heat does not effect them. Accurate metal measurement is done and calibrated for a given temerature.
    Wood moves with humidity and temperature. Humidity is far more important for wood movement. Humidity has no effect on metal unless it causes rust. Much metal working is done with flood coolant to keep the cutter cool and a little bit to keep the work temperature stable.
    They worry about sunlight from a window affecting measurements. Big telecopes are mounted and aligned for a certain temperature, obviously one that occurs at night. Takes several hours after sunset for things to stop moving too fast to be useful.
    Entropy says all the energy pumped into the shop is turned to heat unless some light goes out the window or the dust collector and sand blaster is vented outside.
    Today my shop is about 101, the walls on the south side are 105 and the underside of the roof is 130.
    Bill D
    Bill D

  3. #3
    My short and sweet answer is this.
    Yes metal moves due to thermal expansion but the amount it moves is so minute, in terms of a hot or cold garage, that it's a non issue in a woodshop. I would suspect that your high end squares will read the exact same thing in summer as in winter.

  4. #4
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    The certs are done at 68 degrees, iirc.
    Bumbling forward into the unknown.

  5. #5
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    I’ve noticed the lips on my jointer sit slightly proud during the hottest months in the summer. When it’s 100 degrees plus. My shop is uninsulated my jointer is pretty large the tables are good cast iron and the lips are just regular steel.
    I’ve not noticed any variation in small handtools.
    Aj

  6. #6
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    Maybe Bridge City or one of the other companies that offer over the top priced tools will produce some Invar measuring instruments. You heard it hear first.

    FWIW, plastic drafting triangles are almost always dead on with their angles, at least the Staedtler ones I have are.

    John

  7. #7
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    A 316 stainless steel scale, 12 inches long at 50 degrees, will be about 12.0008 inches long at 100 degrees. (using the engineering toolbox thermal expansion calculator)

    Do machinists have to worry about that? A lot of the time they do. Do woodworkers? Well, not this woodworker

    Figuring out what happens to something like a 45-45-90 triangle is an exercise left to the reader (which is what my professors used to say when they didn't know how to explain something )
    --I had my patience tested. I'm negative--

  8. #8
    At about 80 degrees Fahrenheit all my measuring tools become unusable. But fishing gear reaches peak utility. It's best to schedule accordingly.

  9. #9
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    Quote Originally Posted by johnny means View Post
    At about 80 degrees Fahrenheit all my measuring tools become unusable. But fishing gear reaches peak utility. It's best to schedule accordingly.
    I suggest you put your measuring tools in the fridge when they reach 80 degrees F , take a few brews out to make room if necessary. That way when you get back from fishing they will be cool enough to use.

  10. #10
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    Quote Originally Posted by johnny means View Post
    At about 80 degrees Fahrenheit all my measuring tools become unusable. But fishing gear reaches peak utility. It's best to schedule accordingly.




    10 characters

  11. #11
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    Quote Originally Posted by Paul F Franklin View Post
    A 316 stainless steel scale, 12 inches long at 50 degrees, will be about 12.0008 inches long at 100 degrees. (using the engineering toolbox thermal expansion calculator)

    Do machinists have to worry about that? A lot of the time they do.
    I can't imagine even the most skilled machinist or tool maker using a steel scale (rule) in a situation where 0.0008" deviation would come into play.
    These type measurements would more likely be done with a micrometer or height master. I personally use the Mitutoyo Height Master on a Starrett granite surface plate for critical measurements. My Height Master has a resolution of 0.000010".
    David

  12. #12
    moldmaking, HotRunners specifically - Where I work at my day job we regularly machine and hold +- tolerances of 5microns (a little less than 0.0002in) I believe we have some components that are even 1/2 of that…


    Quote Originally Posted by David Buchhauser View Post
    I can't imagine even the most skilled machinist or tool maker using a steel scale (rule) in a situation where 0.0008" deviation would come into play.
    These type measurements would more likely be done with a micrometer or height master. I personally use the Mitutoyo Height Master on a Starrett granite surface plate for critical measurements. My Height Master has a resolution of 0.000010".
    David
    Last edited by Mark e Kessler; 07-16-2021 at 7:54 AM.

  13. #13
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    A simple no tool method to check fence and blade setups for high precision crosscuts.


    Take a couple of pieces long straight square stock and mark the face and edge on each one.
    Trim the ends off of two sticks.

    Stand them up on a flat surface. slide them together, with the faces facing the same direction see if they fit. Rotate one 180° check again. That's it!
    Repeat the process to check the edges.


    This will tell you if they are square to a much higher degree; much easier to see and measure error, then checking the end with a square. And it tells you square in both planes.
    This is the most accurate way to check your miter-saw fence, table-saw fence, sliding table saw etc. It tells you if the fence is square to the direction of cut, and if the blade is square to the table.

    The longer the sticks the more you will magnify your error. For instance if you use 2"x2"x 50"long you will magnify your error approximately 48 times.
    one quarter of a degree off of square on a 2x2 measure about 0.009" but at 50" it measures 0.218 and this method will double that error to 0.436 gap at the top of your two sticks. So it is easy to see minute error in your fence or blade setup-up.

    By doing a few test cuts and adjusting your fence until the gap disappears you can obtain a very high degree of accuracy with no tools.

    This is similar to a high precision reference cylinder square method.
    You could also use round plastic tube if you want.
    square-cut sticks.jpg

  14. #14
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    To build the pyramids they needed a good level. So they built a wooden trough around the job site for reference. Had a boy or two keep it filled with water to a mark at all times. Worked very well. Definitely better then in Piza, Italy using more modern tools.

  15. #15
    Quote Originally Posted by Bill Dufour View Post
    To build the pyramids they needed a good level. So they built a wooden trough around the job site for reference. Had a boy or two keep it filled with water to a mark at all times. Worked very well. Definitely better then in Piza, Italy using more modern tools.
    But the Piza logo has been much more successful than the Camel cigarette logo

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