How thick sides green bowl

Discussion in 'Newbie' started by Charles Hill, Apr 9, 2013.

  1. hockenbery

    hockenbery AAW Advisor Staff Member

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    Interesting concept.

    I have one counter example that may be a different category.
    I leave sharp edges in natural edge pieces both hollow forms and bowls. I have done hundreds of natural edge hollow forms with the sharp edge.
    Many with no bark. The don't crack. After they dry I ease the sharp edge with 400 grit so they won't cut flesh.

    I try to avoid other sharp edges for esthetics and safety. The rims of bowls can cut badly!
    So my bowls drying for return have no sharp edges.

    It would seem logical that a bowl turned with a sharp edge has tiny cracks in that edge when it comes off the lathe and some might lead to bigger cracks.
    Softening the edge would cut this e tiny cracks away.

    I know rounding over the edge of the base on end grain hollow forms helps keep them from cracking.
     
  2. MichaelMouse

    MichaelMouse

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    The crack on the edge opens downward on a face grained bowl. Less strain in the shoulder droop direction than the lateral, so it really takes a heart check at the wrong angle to lose a piece. Not to mention, rounding means there will of necessity be sections of grain shorter than the wall thickness. You just cut them that way. Some other factor must be the cause of failure, because thousands of blanks in my shop as well as others' have survived without any effort to round the rim.

    Bark up design closes edge cracks given normal mechanical force.
     
  3. MichaelMouse

    MichaelMouse

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    I think your "rough surface" is a straw man. Enjoy demolishing your self-created opponent. As I said initially, easiest cut produces the best surface naturally. The rest is your fabrication. Why would you assume I would deliberately make grooves more than the 1/4" rim imbalance developed during drying? None of the pictures I attached even hint at something like that. Did you make something of your own out of the images as well as the words?

    Imbalance is a strange concept for you? It doesn't necessarily mean stability-destroying heavy versus light weight. It means the rim is not the same in all locations. We'll accept Webster's "out of proportion" definition and run with it, OK? It describes things pretty well. In the pictures, you see imbalances of a quarter inch or so between end and face grain radii. Someone would have to have nubs projecting greater, or digs deeper - properly placed, of course - to force removal of more stock, as you suggest. Note, that by taking off less wood after curing I could get a reasonably symmetrical (though unbalanced) oval form if I want one.
     
  4. hockenbery

    hockenbery AAW Advisor Staff Member

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    Mm
    So after all this you are agreeing it is easier to return a smooth surface?
    Wow!
    A few days you criticized the bevel riding push cut and then posted videos of the bevel riding push cut as your preferred method.

    Woodturning lacks a common language. But .....
     
    Last edited: Apr 12, 2013
  5. robo hippy

    robo hippy

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    I don't think MM uses a bevel rubbing cut for his finish cut. It isn't easily visible from his video clips. It is more of the so called 'shear scrape' with his broad nose/continental gouges. 2 handed push cut. Interesting cut, but I prefer the bevel rub cut. The higher shear angle on MM's style cut does a good job, but I find rubbing the bevel leaves a bit cleaner surface, especially on really difficult woods.

    robo hippy
     
  6. hockenbery

    hockenbery AAW Advisor Staff Member

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    we are seeing different things. when I do shear scrapes the bevel is close to 90 degrees to the wood surface. when I looked at MM's videos the outside cuts I see the outside cuts as bevel riding especially where it cuts off the wood. The inside is less clear so it could be something different maybe more cutting with the tip. you seem to be seeing something different any videos could be misleading me. He does a good job as you say.
    For me the the side ground bowl gouge is does the work much faster allows cutting to the bottom center of the bowl. The near vertical cutting angle is what you get with the side ground bowl gouge when pulling on the outside or shear cutting on the inside.
    if I can sand a bowl with 220 on the outside an 180 on the inside I'm happy!

    I have one of those shallow spindle roughing gouges. They are great but very unforgiving if you come off the bevel and will skate backward just like a skew. I think they outperform the u shaped spindle roughing gouges in speed of material removal and it leaves a nice surface.

    If you are coming to Tampa we could play with it. I'd enjoy seeing you come off the bevel on the outside of a bowl. we could probably sell tickets to raise money for the EOG.
    Al
     
    Last edited: Apr 14, 2013
  7. robo hippy

    robo hippy

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    His inside cuts are off the bevel, can't remember about the outside cut so much. The advantage of the continental gouge is that it has a larger ,sweet spot' than other fluted gouges. I think he used the same cut on the outside as well. Interesting thing is that with this high angle shear cut, the shavings come off with a twist type curl. I can get the same cut with Doug Thompson's fluteless gouges, but I rub the bevel.

    I won't be able to make it to Tampa. I am really disappointed, but have a conflicting event. Fishing trip to a conservation lake in NW Ontario Canada with my 90 year old/young Dad, a couple of brothers, brother in law, cousin in law, and a few others, or Tampa. Well, no thought to it, have to fish. I will be in Phoenix next year.

    robo hippy
     
  8. hockenbery

    hockenbery AAW Advisor Staff Member

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    Good luck with the fish!
     
    Last edited: Apr 12, 2013
  9. Ron Rutter

    Ron Rutter

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    Robo. What lake are you going to? My old (original) stomping ground is Dryden. Fantastic fishing!! Ron.
     
  10. MichaelMouse

    MichaelMouse

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    Off the bevel as in some clearance angle, but you have to consider that the tool is supported against the work ALONG the edge not in a narrow tangent behind it. if you examine the shape produced by the tool, it's pretty easy to see what's happening. http://i35.photobucket.com/albums/d160/GoodOnesGone/7-Surface-In.jpg Very difficult to show a cut happening inside the bowl with the clarity of one outside, but the gouge is held precisely the same. The fairly steep shear portion of the cut becomes shallow where the tool is supported on the work. Couple shallow cuts followed by a more visible deep one in this cutaway. Look at the negative image, as shown here. http://i35.photobucket.com/albums/d160/GoodOnesGone/5-Cut-Shapes.jpg The gouge shears across, then transitions to a slice as the tool advances. This broad support/guidance, and the fact that the non-engaged portion of the gouge curves away from the work, eliminates danger of a catch, and nearly eliminates tearout even in inside areas of rapid curvature.

    While not the best of focus in this use shot, you can see, if you study the shavings, that one edge is smooth, the other feathered. The smooth thicker edge is sheared from the previous cut, the feather the result of the extremely thin slicing exit. The twist, by the way, comes from one side of the shaving being shorter than the other. http://i35.photobucket.com/albums/d160/GoodOnesGone/12_1024.jpg

    Gross shavings show things pretty well. http://i35.photobucket.com/albums/d160/GoodOnesGone/W-ShavingsDemo.jpg

    Since shear is a high pitch, high friction phenomenon, and the slice low and lower, I can reduce the shear by skewing the gouge back along its bevel to get a nearly effortless cut.
     
  11. MichaelMouse

    MichaelMouse

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    Never disagreed. But, if you think, the easiest thing to cut is air, not wood, which makes turning an extremely irregular shape less a strain than maintaining continuous contact, no? Your bowl gouge "digging" example tells me it's improperly presented, pure and simple.

    I never criticized a push cut. Best on two counts, actually. Keeps the contact point at arms length, and keeps the operator completely out of the throw zone if it can be accomplished with a low pitch angle. Problem is, a high sharpness angle, which demands a high pitch angle, is what people use on "bowl" gouge bottoms. Even if they drag the heel, they're making a high-resistance cut, and their head and possibly even shoulder often crosses the line into the throw zone. Better to drop the handle, sacrificing control, and suck shavings making a pull cut with physical interference from the headstock and visual from the larger diameter rim on a bowl bottom than to lean into harm's way as you approach the rim, where the kinetic energy of a detached chunk is the highest.

    As to what constitutes "bevel-rubbing," my position is clear - along the edge, not perpendicular to it. If perpendicular, you can have the tool roll on you too easily. Vary the grind, and it's a big catch.
     
  12. robo hippy

    robo hippy

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    Ron,
    We drive in to Kenora, and Lake of the Woods, then fly north about 60 miles to Rowdy lake. There are several lakes there that we can do short portages to. Lake trout, Walleye, Northern, a few small mouth, and one of my brothers got a 'rainbow' pike, which is a hybrid northern/muskie. Beautiful. Mosquitoes have been minimal, black flies bothersome, but just nothing to do but eat, fish, and be disgusting guys for 5 days. I am still trying to get a trophy northern. Much more fun hunting them than finding the walleye.

    robo hippy
     
  13. Ron Rutter

    Ron Rutter

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    Robo. If you really want that Northern just take the front seat & cast the shoreline as you troll, especially the points!! Cheers. Ron.
     
  14. robo hippy

    robo hippy

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    Miles of rushes, lily pads, and points. Got one big one once right off a beaver dam. Some times they come up from casting, and one year it was really hot, and the only way we could find them was to troll. You never know. I have gotten some out in the flat open areas when every one else was jigging for walleye. It is fun, you have to hunt them down. Fresh water barracudas! I do prefer the Dare Devil spoons too. No substitutes. Even had a 12 inch pike take a 3 inch spoon.

    robo hippy
     
  15. hockenbery

    hockenbery AAW Advisor Staff Member

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    I use the Ellsworth. Grind and get curled shaving when I do light cuts.
    When removing an 1/8" of wood or less with a bevel riding cut they start coming off curly.
    I never thought much about the curl being anything special.

    When I shear scrape they come off like angel hairs. These seem special.

    When I'm rough Turning a bowl. I make roughing cuts with 1/2-3/4 wide shavings.
    When I get close to the shape. I make a bevel riding cut removing about a 1/4" of wood
    Then one removing about an 1/8" of wood. That is a good surface for drying

    When i Return the bowl
    I balance the rim with the bowl jammed on an open chuck,
    I true the rim which balances the weight some.
    I make a cut starting as a 1/16 at the foot and ending at 1/4" near the rim.
    The surface is usually back in round about a 1/3 of the way up
    Next cut starts riding the bevel on the round wood not cutting, about a 1/3 from the bottom, where it begins a cut on the out of round at a 1/16 to a 3/8 at the rim.
    This might need a few more cuts or might not. If it needs more working from round to begin the cut at the out of round.

    Once the outside is back in round I take light cuts to refine the shape if needed

    Next an 1/8 foot to rim
    Next a 1/16 foot to rim
    Next a 1/32 on any high spots.
    Then I shear scrape.

    I also just hollowed a small opening with a Michelson ground gouge. Shaving came out curly.
    Small shavings seem to be curly for me.

    Al
     
    Last edited: Apr 15, 2013
  16. robo hippy

    robo hippy

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    Al, I don't have pictures, but the two types of curls are very different. Can't really describe though. The high shear angle ones are like you grabbed the two ends and twirl them between your fingers several times. Not at all like any I can get with my standard gouges.

    The shear scrape shavings come off 'finer than frog's fur' as my Grandma used to say. Wait, there isn't any fur on a frog! You can't see it because it is so fine.'

    robo hippy
     
  17. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Is it a helix like pulling a decorative ribbon with your thumbnail? Sorry, that is not exactly a guy question. :)

    The other curl that comes to mind is a spiral -- as in, Spiral of Archimedes.

    I get the former with a very high shearing orientation of the gouge except cutting with the bevel slicing into the wood as opposed to shear scraping.
     
    Last edited: Apr 15, 2013
  18. MichaelMouse

    MichaelMouse

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  19. hockenbery

    hockenbery AAW Advisor Staff Member

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    I'm not sure the shavings have any particular meaning.

    I collected some from a piece of maple using an Ellsworth gouge 5/8 diameter bar using a pull cut, push cut and shear scrape the photos are in that order.
    gouge was fresh off a 60 grit Norton 3x wheel no honing.

    These are light finish cuts
    the pull cut leaves a 220 surface, the push cut a borderline 220 surface, the shear scrape a borderline 320 surface.
    This was a convex shape.
    The 4 mm wrench is for size comparison.
     

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    Last edited: Apr 16, 2013
  20. robo hippy

    robo hippy

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    I can't really see any difference in MM's pics other than the second pic has wider shavings. With standard gouge orientation, you get more of the Archimedes type spiral, which I can get with a scraper, and as they fly off the tool and lathe they do helix a tiny bit. Yours and MM's are more the helix type I guess. I think the high shear angle lifts one side off first, and the other side of the shaving comes off second, so maybe that is why it twists. With the Thompson fluteless gouge, I can lift a solid quarter to half dollar size shaving off the dead center, rather than a continuous shaving. The high shear angle, and I am at 60+ degrees is much better for getting under the wood and gently lifting, compared to more standard (level) held gouges that have deeper flutes. When you drop the handle, the wing will be at a much steeper shear angle, of 45 or more degrees, and the longer edge again does a better job of lifting. This also gives a longer 'sweet spot' for cutting when compared to the nose of the gouge.

    robo hippy
     

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