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  1. #31
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    Quote Originally Posted by powderpost View Post
    Theoretically, one would run the board over a surfacer with the cup side down to remove the 1mm cupping.
    Which leaves the board 11mm thick in the middle and 12mm thick at the ends.

    Then one wold run the surfaced board through a panel planer to make the second side parallel to the surfaced side. The board would end up 10mm thick, theoretically, that is. The correct answer, theoretically, would be 10mm..

    Jim
    This would take the 1mm from the 12mm ends but nothing from the 11mm middle, leaving the board 11mm thick.

    OR

    Hand-plane 1mm from the middle where it bows upwards, tapering out to nothing at the ends.
    Next, flip the board and hand-plane the ends by 1mm, tapering out to nothing at the middle.
    We are talking theoretical, and theoretically it should be possible to take 1mm from one part of a board but not from another.

    It's perfectly clear to me, and I thought my drawing was too.

    Actually, in my opinion, the onus is on the OP, who provided both the question and the answer, to prove his case. It's not up to me. I'm just another 'guesser', and my guess is 11mm.
    ... Steve

    -- Monkey see, monkey do --

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  3. #32
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    Quote Originally Posted by sinjin View Post
    Simple but tricky question. If i had a plank of timber 12mm thick and just by chance it had a 1mm bow right in the center.
    Board lenght doesn't matter...say 1000mm for arguement sake.
    I need to plane the board dead flat and also dead parallel what would be the maximum thinkness i could get the plank
    when it is finished. This is a theoretical answer not from a practical point of view. Would the board end up being
    11mm thick or 10mm thick.
    Sinjin
    I think some of you missed the question.

    "This is a theoretical answer not from a practical point of view".

    It's not a wood working question.

    It's a mathematic theory question.

    The answer is 11mm.

    Cheers Tim
    Some days I turns thisaway, somedays I turns thataway and other days I don't give a stuff so I don't turn at all.

  4. #33
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    Quote Originally Posted by jefferson View Post
    Steve, get some crooked boards out and tell me you come up with 11mm. My best advice is to avoid boards with crooks. Typically, quarter sawn boards won't twist the same as rift sawn boards.

    And if a board is 1mm out on one side, it must be 1mm out on the other. Low or high on one side, same on the other.

    Again, do you want me to send some boards? At your cost if you are wrong.

    What sort of machines are you running? I assume both a buzzer and thicknesser. Which makes we wonder why you are saying 11mm. From my experience - and it follows industry standards - a rough sawn 25mm board comes down to 19mm when dressed.

    That's not a deviation of 1mm.

    Perhaps you can educate us all.
    Forget the planer and thicknesser if they can't do it. If you take a hand-plane and do it exactly as shown in my earlier sketch, you'll end up with an 11mm board. (In theory, not practice. In practice none of us could do this because we don't have enough control over the plane.)

    Don't forget, we're not looking at what you get 'in practice', using a buzzer etc, but the 'theoretical' answer. 'In theory', under 'ideal' conditions, you should be able to remove the exact amount of wood that's needed.

    Not trying to get into arguments, by the way, but can't help supporting my view.
    ... Steve

    -- Monkey see, monkey do --

  5. #34
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    Quote Originally Posted by Tim the Timber Turner View Post
    I think some of you missed the question.

    "This is a theoretical answer not from a practical point of view".

    It's not a wood working question.

    It's a mathematic theory question.

    The answer is 11mm.

    Cheers Tim
    Thanks Tim, We were making the same point at the same time, but you pipped me. (And you explained it better, I think.)
    ... Steve

    -- Monkey see, monkey do --

  6. #35
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    Quote Originally Posted by sinjin View Post
    Simple but tricky question. If I had a plank of timber 12 mm thick and just by chance it had a 1 mm bow right in the centre.

    Sinjin

    I think you should stop buying your timber from the big sheds and buy it from a proper timber yard, then you won't have this problem.


    Peter.

  7. #36
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    Quote Originally Posted by Hermit View Post
    Thanks Tim, We were making the same point at the same time, but you pipped me. (And you explained it better, I think.)
    As my old maths teacher used to say.

    Read the question.

    Then read it again before you answer.

    There are no marks for a correct answer to the wrong question.

    But it's been a good debate.

    Cheers

    Tim
    Some days I turns thisaway, somedays I turns thataway and other days I don't give a stuff so I don't turn at all.

  8. #37
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    Quote Originally Posted by Tim the Timber Turner View Post
    As my old maths teacher used to say.

    Read the question.

    Then read it again before you answer.

    There are no marks for a correct answer to the wrong question.

    But it's been a good debate.

    Cheers

    Tim
    In this case there are no marks for the right answer to the right question either. Just a good exercise in logic.
    I still think we should have one a week, but I'm not putting my hand up.
    ... Steve

    -- Monkey see, monkey do --

  9. #38
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    Quote Originally Posted by Tim the Timber Turner View Post
    I think some of you missed the question.

    "This is a theoretical answer not from a practical point of view".

    It's not a wood working question.

    It's a mathematic theory question.

    The answer is 11mm.

    Cheers Tim
    Agreed... but..... theoretically speaking, a board 12mm thick with a 1mm cup in it is now not 12mm thick but theoretically 13mm thick. So the answer is still 10mm.

    So the answer of 10mm is still theoretically and mathematically correct.
    Jim
    Sometimes in the daily challenges that life gives us, we miss what is really important...

  10. #39
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    Quote Originally Posted by powderpost View Post
    Agreed... but..... theoretically speaking, a board 12mm thick with a 1mm cup in it is now not 12mm thick but theoretically 13mm thick. So the answer is still 10mm.

    So the answer of 10mm is still theoretically and mathematically correct.
    Jim
    Sorry Jim that doesn't make sense.

    Don't you agree with Hermit's drawing?

    As one of your famous Queenlanders once said.

    "PLEASE EXPLAIN"

    Cheers

    Tim
    Some days I turns thisaway, somedays I turns thataway and other days I don't give a stuff so I don't turn at all.

  11. #40
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    No I don't agree with Hermits drawing. With a 1mm cup in the board, the board now becomes 13mm thick not 12mm thick, theoretically.
    Been an interesting exercise. Perhaps the moderators can see fit to include a "Conundrums" component to the board?

    Jim
    Sometimes in the daily challenges that life gives us, we miss what is really important...

  12. #41
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    If we look at it theoretically I'm wondering why you would plane it all. To retain the full 12 mm you would steam bend it back dead flat and dead parallel by clamping between two straight pieces. Bit of work but it saves the one or two mm. and is easier then planing.

    Of course that would be a flat work exercise and real turners don't do that kind of thing.



    Peter.

  13. #42
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    Quote Originally Posted by powderpost View Post
    No I don't agree with Hermits drawing. With a 1mm cup in the board, the board now becomes 13mm thick not 12mm thick, theoretically.
    Been an interesting exercise. Perhaps the moderators can see fit to include a "Conundrums" component to the board?

    Jim
    Jim, the board is not 'cupped' or 'twisted', only 'bowed'.
    Second, it can only be 13mm if you include air. Air doesn't count as part of the thickness of a board.
    I don't know how you can disagree with the drawing. It says it all.

    This isn't a conundrum - it's a plain logical exercise, with only one possible answer - 11mm.

    Forget thicknessers, buzzers, etc and look purely at the logic of removing unwanted material only where necessary as shown in my sketch.
    ... Steve

    -- Monkey see, monkey do --

  14. #43
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    Quote Originally Posted by Sturdee View Post
    If we look at it theoretically I'm wondering why you would plane it all. To retain the full 12 mm you would steam bend it back dead flat and dead parallel by clamping between two straight pieces. Bit of work but it saves the one or two mm. and is easier then planing.

    Of course that would be a flat work exercise and real turners don't do that kind of thing.

    Peter.
    Yep - that's what I suggested in an earlier post. If it was reasonably short that would be easy.
    Unfortunately, though, the question stated that the timber must be planed, so that rules out this method.
    ... Steve

    -- Monkey see, monkey do --

  15. #44
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    Quote Originally Posted by Hermit View Post
    Yep - that's what I suggested in an earlier post. If it was reasonably short that would be easy.
    Unfortunately, though, the question stated that the timber must be planed, so that rules out this method.
    Great minds think alike but the examiner is posing the question asking about planing because he doesn't realize there are more ways to skin a cat.


    Peter.

  16. #45
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    Quote Originally Posted by powderpost View Post
    No I don't agree with Hermits drawing. With a 1mm cup in the board, the board now becomes 13mm thick not 12mm thick, theoretically.


    Jim
    I agree 13mm.

    Theoretically you remove 1mm off each side to make it flat.

    13 minus 2 = 11mm

    The answer is 11mm

    Jim I know you can add up because you have to count all them little bits of wood before you stick them back together.

    I think you are not serious and just having a stir?love it!

    Just to change track.

    Isn't it great that we can all be in different parts of the country and have a debate like this.

    Even if half of you are wrong.

    Cheers
    Tim
    Some days I turns thisaway, somedays I turns thataway and other days I don't give a stuff so I don't turn at all.

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