Everything I turn ends up round!

Discussion in 'Newbie' started by Mark Warden, May 16, 2009.

  1. Mark Warden

    Mark Warden

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    Iv'e been trying to make a natural edge bowl that ends up oval like I see in some of the pics on here.I don't know what i'm doing wrong but till I get the outside of the bowl shaped it's round.Is there some formula for the blank size and shape or what?:confused:
     
  2. Rick H

    Rick H

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    Round

    Well to me it is more of an optical illusion that the NE bowls are oval. They are actually round. The fact that you use a half log to turn then from you end up with a bowl that has higher rim on the crown of the log and a lower rim on the sides of the log. That is what gives the look to the bowl that it is oval.
    My guess is that you are trying to use too much of the top of the half log. If you want a 6" NE bowl do not start with a 12" log and cut the center 6" out. Too much of the rim is on the top. Start with an 8" log and the sides of the rim are down lower then and that is what gives you that oval look.
     
  3. Vaughn

    Vaughn

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    Not wanting to argue, but NE bowls are not necessarily round. If the blank is as wide as it is long, then yes, it will be a round bowl. If the blank is longer than it is wide, it will be an oval bowl.
     
  4. Bob Edwards

    Bob Edwards

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    Round V Oval

    I'd like to hear you explanation of how you get a oval bowl from a standard lathe without any apparatus to turn the work in an an orbital rotation.
    What you have with a natural edge bowl is a round bowl with two apposing wings that extend vertically.
    The attached is one half of a log mounted between centers in such a way that point A & D are in the same axes. Points B & C are also in the same axes. As the bowl is hollowed from the right and the bottom is shaped from the left the four points will come closer together. When points A & B are 1/4 inch apart, points C & D will also be 1/4 inch apart and the rim of the round bowl will be 1/4 inch wide.
     

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  5. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Turn it green and then let it warp.
     
  6. GeorgeH

    GeorgeH

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    I must be doing something wrong. When I turn an "oblong" object, bowl or otherwise, I turn it on variable axis by mounting my piece a bit off center for one side, the same amount off center for the other.
    If you folks are turning oblong pieces on a single axis you've got more talent than I have. An oblong blank, longer two sides than it is on the other two, can be turned "oblong" but two of the sides will never feel the tool and the depression cut to hollow it out for a bowl isn't going to be oblong.
     
  7. Rick H

    Rick H

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    The whole point is that the peice can be long and thin. Yes the long axis will have lets say a 8" length. The width can be 4". But the 8" part will be 3" tall and the 4" side may only be 1" tall.
    So looking down from the top the peice seems to be oblong.
    Really the sides were never there, you were turning air on the 2 sides when you were turning the round object.
    But in reality it is round, the sides have just been cut off. You can get the same type of look making a 8" round bowl and then cut 2" off of the left and right sides.
    The slope on the sides of the bowl, or the diameter of the half round log will dictate how oval the object looks.
     
    Last edited: May 16, 2009
  8. patrick stein

    patrick stein

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    n.e.bowls

    when marking the blank for cutting on bandsaw are u using a round template or dividers. dividers will give more oblong shape when sawing. circle template will end up more round.
     
  9. Joe Greiner

    Joe Greiner

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    Oh, boy! You're turning an inverted circular cone with sloping sides. At the "top," it's wider than part way down, where the cone intersects the wood. So, from above, it looks oval.

    If you turn a cylinder, with straight sides intersecting the log, it'll be round. Unless you turn it very green, and let it warp to a real oval.

    There's no magic involved, just geometry and Mother Nature.
     
  10. MichaelMouse

    MichaelMouse

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    I think you are referring to visual effect rather than actual shape. http://i35.photobucket.com/albums/d160/GoodOnesGone/While-The-Glue-Dries.jpg That's from choice of a blank longer than wide, as has been said. If you want an actual oval, be prepared to carve the inside, or buy a very special type of lathe.

    If you cut your blank, whatever the original dimensions, so that you have no air left at the edge, it will look round. http://i35.photobucket.com/albums/d160/GoodOnesGone/Linseed.jpg It's still an (un)natural edge, but the visual effect is of a round piece. http://i35.photobucket.com/albums/d160/GoodOnesGone/Profile-Oil.jpg Note that there is not much slope, as Joe says, which is why it looks round even with varying depth.
     
  11. Steve Worcester

    Steve Worcester Admin Emeritus

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    Use green wood, turn it as thin as you can, and it warps oval.
    Every time (except mesquite because the shrinkage rate is the same on axis').
     
  12. Mark Warden

    Mark Warden

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    Thank you everyone I think i'm trying to start out too thick. This pic MM posted is what i'm trying to do. "I think you are referring to visual effect rather than actual shape. http://i35.photobucket.com/albums/d1...Glue-Dries.jpg " I turned a winged bowl like I saw on youtube and it pretty much came out in the shape I was looking for but much thinner than I was trying to get.
     
  13. Vaughn

    Vaughn

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    I should have been more clear. You are correct, it is round with opposing wings. It can have the appearance of being oval.
     
  14. hockenbery

    hockenbery AAW Advisor Staff Member

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    Mark,

    Thinner blank should help.

    Try blanks 8" x 6 x 3 or 8 x 5 x 3.

    the fixed elements in the design are the two rim points (opposite bark edges) that are cut once by the tool. create the chuck mount and notion of where the bottom will be and cut a curve from the bottom to your 2 rim points.

    this will produce an oval shaped shallow bowl. the oval is the bark contour.
    a relatively easy piece to turn

    Put on a blank 5x5x8 and you get a taller more cylindrical bowl that can be quite dramatic in a wood like walnut with a top sap ring. This shape is tough to hollow.

    -al
     
  15. bill easterling

    bill easterling

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    Round vs.oval

    I just measured a NE bowl I turned and the tall wings are 3 3/4 inches across and the low sides are 3 1/4 inches
     
  16. Joe Greiner

    Joe Greiner

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    Most likely a combination of both effects: geometry and warping.

    For a blank with the bark still on, the cambium is the first to dry. So NE pretty much demands green turning, and/or glue reinforcement.

    I just measured this one: http://n-fl-woodturners.org/images/2008-12/2008-12-07.jpg
    About 9" 'long' x 8" 'wide' at the top, and about 7.5" x 7" at the (Tropic of Capricorn?).
     
  17. Mark Warden

    Mark Warden

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    Thanks again everyone I will put all the advise to good use and post some pics whn I get one I like.
     
  18. MichaelMouse

    MichaelMouse

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    Some information above needs a bit of explanation or modification. Food for thought.

    Broader form ratios allow more bark exposure. http://i35.photobucket.com/albums/d160/GoodOnesGone/Biggest-Ever.jpg If you cut nearly vertically through the bark you have just a thin layer showing which almost demands reinforcement as you turn to prevent loss. CA works great. Try not to get it on the wood itself, but rather in the cork layer just above the cambium and below the outer bark. You'll appreciate having it there every time someone tries to handle it. The sapwood is generally wetter and less organized than heartwood and shrinks at a greater rate, so using the glue also minimizes chances of ending up with bark loops over a shrunken base. Don't add CA after you're ready to sand. http://i35.photobucket.com/albums/d160/GoodOnesGone/Maple-Large.jpg

    If the bark just won't stay on, as in woods which have had bacteria working under it for a bit, eating that nutritious cambium, do not despair. You can knock it all off and burnish the edge or char/color it. http://i35.photobucket.com/albums/d160/GoodOnesGone/216695ce.jpg

    The last is one of my "unnatural edge" pieces, where the log splitter designs the rim for me. I have a lot of fun with them, though they are not as predictable in outcome as a log section piece. You can even cut through and through, unlike suggestions to start thinner, producing interesting views like these. http://i35.photobucket.com/albums/d160/GoodOnesGone/Beech-Wing.jpg

    Keep things thin at 1/4 inch or more for good bark definition, and you can have some good fun with a neat genre of turnings that require no embellishment. Doesn't even have to appear oval. http://i35.photobucket.com/albums/d160/GoodOnesGone/Weirdo.jpg
     

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