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

  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
    Actually some of our cnc machines are totally enclosed and conditioned as we found even with controlling the coolant temp we were still seeing dimensional changes with the tooling, bed, ect…
    Last edited by Mark e Kessler; 07-14-2021 at 9:26 PM.

  7. #7
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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

  8. #8
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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 )
    --Certainty is the refuge of a small mind--

  9. #9
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    I would expect the variation in measurements due to expansion or contraction of metal rulers in a woodworking shop would be insignificant compared to the expansion and contraction of the wood itself with moisture content especially if all components are cut and assembled under similar conditions. I assume the 89* you refer to is temperature (I hope in F not C ), when I first read it I thought your triangle was one degree out of square, that would be a whole new issue.

    Just to take this one step further, I've often wondered about large machinery components that are built in a shop, shipped thousands of miles to a jobsite sometimes in a different climate and then assembled along with other components built in other shops. I remember working on a jobsite where a large ship loader was being assembled and seeing the main body bent like a banana because the sun was shining on one side and the other side was in the shade.

  10. #10
    At about 80 degrees Fahrenheit all my measuring tools become unusable. But fishing gear reaches peak utility. It's best to schedule accordingly.

  11. #11
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    Thermodynamics deals with the relationship between heat and other forms of energy. Coefficient of expansion is the change in dimension of different materials due to temperature change. I really don't understand how trig comes into play here either. Calculating the angles and side lengths of shapes has nothing to do with temperature change.
    Last edited by Richard Coers; 07-14-2021 at 10:57 PM.

  12. #12
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    I think the most significant concern in your situation is the thermal impact on your adult beverage. Prudent management would be limited time exposure to the (external) elements using the bottoms up protocol!

  13. #13
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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.

  14. #14
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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

  15. #15
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    Accuracy is more of a mindset than a toolset!

    It is about:

    Knowing the variables
    Understanding the relationships between parts.
    It is about knowing how to check and reference parts.
    And developing a process to check and verify.
    And having the discipline to follow your process.

    Expensive tools wont give you this.... Beer may help.

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