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How thick sides green bowl

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

  1. Charles Hill

    Charles Hill

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    How thick should I make my green bowl sides. For the best result
     
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

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    The rule of thumb for the thickness of green wood that you plan to rough turn and then air dry before finishing is approximately one-tenth of the bowl's roughed out diameter. Don't go measuring this with a micrometer -- eyeballing it is close enough. See the figure below.

    bowl-thickness.jpg

    Here are some other guidelines:

    • Round over the top edge of the bowl. This helps to reduce stress concentrations that can occur if there is a sharp corner.
    • Coat the bowl with Anchorseal or something similar or otherwise do something to slow down the rate of drying. Fast drying is more apt to lead to cracks.
    • Some woods warp more than others so take that into consideration and make the roughed turning thicker. It is disappointing if you have a nice bowl that warps too badly to be able to get it round again after drying.
    • Bowls can have all sorts of shapes (spherical, paraboloid, calabash, etc) and all of these shapes have an effect of the way that the wood will behave or misbehave while drying. The only way to know for certain is by experience.
    • There is a high likelihood that a bowl that has an abrupt change in bottom curvature such as fairly flat bottom and steep sides is a very good candidate for cracking during drying. So it is advisable to shoot for creating a well behaved curvature that is fairly continuous sort of the way that is shown in the figure . This is probably one of the more difficult parts of bowl turning for a beginner who is doing well just making a bowl that holds together while turning.
     
  3. hockenbery

    hockenbery AAW Advisor Staff Member

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    Bill hit the important Parts.
    I did a demo on turning green wood about a year ago and am doing it again in a few months for another club.

    I start with a 10 minute slideshow which is the handout, then pass around 3 bowls and urn a owl for drying.
    There are diagrams of how wood Ives and a shrinkage chart of some poplar species.
    I think his link will show you're slides.

    https://www.dropbox.com/s/5rl6v4aa8rpc0fl/WORKING WITH green wood.pptx

    I call the following the five habits of successful greenwood turners

    Start with crack free wood
    Work fairly quickly
    Flowing curves
    Even wall thickness
    control the drying

    The deck is sort of stacked against beginners. If you are learning on you own it is hard o get nice curves, even walls, let alone work fast enough to keep the wood from dying on the lathe.

    The smoother the surface on the roughed out bowl the easier it is to return


    Be safe
    Al
     
    Last edited: Apr 11, 2013
  4. MichaelMouse

    MichaelMouse

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    Shape and grain more important than thickness. The 10% business is very popular. It'll guarantee you plenty of wood to do a reshape if you like. If you want to dry the wood faster, go thinner. No reason why a regular grained piece can't be cut to 7% or even a bit less and have enough to be made circular. Not much left over for restyling, though. It'll cure in a bit over half the time of a 1". What you don't want is a broad section of face grain, as in a squared-across bottom. The less slope on the sides, the thinner you can go if you're anxious, and the safer to dry in any thickness.

    It's mechanical stress that exploits the surface checks or cracks which form from uneven moisture loss. And there will be uneven moisture loss, which is why the business of "equal thickness" doesn't apply. When the difference in rate of loss is a factor of ten or twelve, depending on grain orientation, a quarter inch difference in thickness is not significant. In the right place, even a half! To reduce the effect of mechanical stress - squeeze across the grain and droop in the walls - we like to keep the rate of surface loss low, and fiber expanded for as long as we can without growing mildew. Coating or containing are the common ways to do it. It's actually control of the relative humidity that you're trying to accomplish.

    http://i35.photobucket.com/albums/d160/GoodOnesGone/LogEnd.jpg Is a good teacher. Since the earlywood is less dense, it shrinks proportionately more than the harder, denser latewood. The greater the span of earlywood, the greater the total contraction, and the greater the stress on any check on the end grain. Simple mechanics says if you tie a string (earlywood) across a span (two latewood rings) and then try to shrink the string, the span must shorten or the string must break. The same mental string will explain what makes your bowl oval, as well.

    Not sure why a smooth surface on a rough bowl would help anything, but good tool technique will produce one automatically, even when you're hurrying hauling trash out of the way. Turns out the easiest and fastest way produces the best surface, with wet wood easier to slice than dry in most cases.
     
  5. Richard Jones

    Richard Jones

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    the business of "equal thickness" doesn't apply.

    You're saying even/equal wall thickness isn't applicable?
     
  6. dbonertz

    dbonertz

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    Charles,

    The ten percent guideline is there for people learning like yourself. It is a very good guideline to start with until you gain some experience with the woods you're dealing with. A lot of folks do not vary from that guideline at all and are very successful with drying. Cutting the walls thinner as MM suggests will work but is best used after you have gained experience which can take a few years so be patient.

    Your wall thicknesses can very a bit but try and keep an even wall thickness. If nothing else this is great practice while roughing to achieve an even wall thickness and gain the confidence to get the final thickness when finish turning. If you're going to be a little thinner anywhere the bottom of the bowl is a better location. It has less movement therefore will not diminish your ability to finish turn the bowl. Some have suggested this helps make the bowl a little more elastic thus less cracking but I can't say that anyone has proven this theory.

    I think what Al is suggesting with a smooth surface is that when you go to finish turn the bowl the first few cuts will go a little better for you. When you combine the rough surface and warp of the bowl it can make for a bumpy cut for the less experienced. Having said that don't get to concerned with a smooth surface for drying sake be more conscious of form, thickness then surface.

    As a final note, make sure you take the time to practice while rough turning. It is the best time to practice different cuts, forms, looking at the piece to study grain, holding methods, using a caliper to check thickness, how to make a good tenon or recess, turning with the opposite hand rather than the dominate hand, your stance and movement, slower speeds rather than crank it up, cutting while standing out of the line of fire and etc. etc. Most importantly have fun.

    Dale
     
  7. hockenbery

    hockenbery AAW Advisor Staff Member

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    Shape and equal thickness are related.
    A hemispherical bowl is more forgiving with unequal walls.
    I usually rough my bowls with slightly less wall thickness in the bottom 1/3 of the bowl.

    A bowl with sharp angles vertical walls flat bottom it very difficult to dry without cracking.
    Wall thickness is critical

    Hollow forms and once turned bowls even walls and curves are more important.

    I have turned quite a few 3" solid balls from live oak.
    They dry without cracking because the old can move in all directions and the wood has an interlocking grain.
    They end up looking ellipsoid but don't crack
     
    Last edited: Apr 10, 2013
  8. john lucas

    john lucas AAW Forum Expert

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    Everyone is assuming he's talking about twice turned bowls. I do a fair amount of those but most of my green wood bowls are turned thin to completion and just let them warp. Most of these are natural edge style so the warp isn't as noticeable although if they are highly figrued they get lumpy of course.
    I turn them to 3/8" thick or less. Woods that have a tendency to crack I turn 1/4" or even less for small, say under 6" pieces. Many are from limb stock so they may be 4 to 6" wide and 8 to 12" long.
    I can get buy with 1/2" thick if I put them in a paper sack for the first week or so to limit the moisture loss.
     
  9. hockenbery

    hockenbery AAW Advisor Staff Member

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    Smooth surface makes it easier to return the dry bowl.

    If a roughed bowl has bump, ridges, tearout, it will be harder to reshape round and will require more wood removal.
    When I return a bowl I try to turn the out of round to the one or two lines on the outside of the bowl that are in round.
    This yields the largest bowl.
    Rarely do I need to reshape this curve.
     
    Last edited: Apr 10, 2013
  10. MichaelMouse

    MichaelMouse

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    Yes I am. I'll go one further and say that the business of a thinner bottom doesn't apply. Since there's no consistency in dry rate, there's no need to try to be consistent in thickness. What you want to avoid is a long continuous area of wood to contract and exploit drying checks in endgrain. The broad bottom, steep slope syndrome. When you hollow you interrupt these broad areas until you get to the bottom of the bowl. There the continuous portion will have the greatest absolute shrink. http://i35.photobucket.com/albums/d160/GoodOnesGone/Picture-Package-14.jpg Shows the mortise on the bottom of a bowl. Shrink from green to ~10% has caused the 1/8" difference you see. 1/8 over 2 should come out to 7/8 over 14, but it doesn't, as you can see. You can also see that the walls are 3/4 or so at the top, and the bottom is as thick as the entire piece. None of that stuff is important to survival.

    Steeper sides squeeze proportionately more. http://i35.photobucket.com/albums/d160/GoodOnesGone/Eleven-Across.jpg

    http://i35.photobucket.com/albums/d160/GoodOnesGone/Eleven-Half-Long.jpg

    Shoulders droop depending on how close the rings are and what the slant is. http://i35.photobucket.com/albums/d160/GoodOnesGone/Edge-Droop.jpg

    NB I haven't ever had any problem leaving the edges sharp while drying. But it makes sense to round them over in case you should brush against them after they dry.
     
  11. MichaelMouse

    MichaelMouse

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    Require more wood removal? Something happening other than the normal shrink because you didn't make things slick? The difference along versus across grain will be the same regardless.

    http://i35.photobucket.com/albums/d160/GoodOnesGone/BroadOutProgressive.jpg The short (end) grain needs to be cut to get to circular.

    Inside http://i35.photobucket.com/albums/d160/GoodOnesGone/BroadInStaging.jpg The long grain needs to be cut.
     
  12. hockenbery

    hockenbery AAW Advisor Staff Member

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    MM,
    The wood shrinks the same,
    If you are returning a rough surface you sort of have to go through the roughing process again
    Any ridge will have the same undulating warp of the rim.

    The final surface of the rough turned bowl is just a light pass with the bevel riding push cut.
    Something you could sand with 120. Nothing special.
    My beginning bowl students usually get this by their 2nd or 3rd bowl.

    If you are returning a clean surface and you line up the rim of the dried blank well you can use Finnish cuts to turn down to two thin lines of the dried surface.
    95 % Of the time this will be real close to the final curve and the rim has the smaller diameter of the dried blank.

    It just simple, if you leave a rough surface you will be turning away more of the outside to get a finished surface.

    With your post in the middle method it probably doesn't matter as you are stuck with what the post allows.
     
    Last edited: Apr 10, 2013
  13. Steve Worcester

    Steve Worcester Admin Emeritus

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    I would mostly agree in that close counts, but I haven't found a cracked bowl yet that I would attribute to the wall thickness variations vs a surface or latent defect.
    Figure you leave the tenon on, that adds extra depth (thickness)
     
  14. robo hippy

    robo hippy

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    The 10% for twice turned bowls is a guide line, and not an exact measure. With some woods it is more than you need, and with other woods, you need way more, or have to boil them to be able to twice turn, and Madrone is one of those woods. With a twice turned bowl, you can leave the bottom a bit thinner than the walls as it moved some what differently than the sides and end grain. Having a smooth surface does contribute to more even drying stresses, but what you don't want is big differences, which can create more stress in some areas, and stress is relieved by cracking. Rounding over the rims really helps as well.

    Drying is a whole different art, and will change for every different piece of wood you turn. Also, your local environment contributes a lot to this process as well. A lot of experimenting is necessary.

    robo hippy
     
  15. john lucas

    john lucas AAW Forum Expert

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    Boy I'll agree with Reed on that. Where you live has huge amounts to do with how the wood dries and that's probably why there are so many different techniques. What works for me might not work for you and vice/versa. If we all had ideal storage areas it might be different but most of us are forced to store the wood in less than ideal situations and consequently simply have to experiment and find what works best for us.
     
  16. hockenbery

    hockenbery AAW Advisor Staff Member

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    Yes indeed humidity is our friend!
     
  17. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I agree with Steve that defects in the wood are generally the catalyst for cracking, but there are some types of wood that just love to crack at the slightest provocation (madrone mentioned by Reed).

    As you say, good tool technique results in a smooth surface regardless of its role in cracking. FWIW, let's consider a worst case scenario of what may happen as a result of really bad tool technique where a bowl gouge may be used more like a digging instrument and the resulting damaged surface that bears some resemblance to a furrowed field.

    I believe that the gist of the above paragraph has to do with shrinkage vs. grain orientation and wood thickness. I agree, but I think that it overlooks the effect of surface discontinuities on internal stresses that are created during the shrinking process.

    The internal structure of the wood plays a significant role in wood movement, but there are other external factors that can create "stress risers" AKA "stress concentrations". These terms refer to the concentration of high stresses acting on relatively small regions due to discontinuities in the shape of the surface.

    Thinking about the "bad tool technique" mentioned above, these discontinuities include rough edges on corners and openings, cracks, grooves, transitions with sharp corners, surface irregularities and other such things. These stress concentrations occur because the strain (movement) is different on each side of a discontinuity. This sort of failure is self propagating because the resulting material yielding weakens it and increases the magnitude of the stress concentration. When combined with the right internal grain pattern the chance of a crack developing increases over the chance of a smooth surface developing a crack.

    Stresses can be due to either internal or external forces or both. It doesn't matter if the material is homogeneous or not -- the difference is that the nature of stress induced cracking is more likely to be analytically predictable in homogeneous materials.

    In the real world, will this make a difference? Maybe, but it is mostly a moot question because we use good tool techniques and take various measures to minimize the chance of cracking.

    I haven't either, but then I haven't turned many bowls out of crack prone wood and besides that I seldom twice turn things.

    At the all day demo at our club last Saturday, Mike Mahoney said that he turns a large number of bowls and since he started rounding the rims a few years ago, he said that he saw a significant enough reduction in cracked bowls to continue rounding the edges.

    And I agree with you that rounding the edge of the rim is a good idea even if sharp edge cracking has not been a problem. It only took one close encounter of the bowl kind with my fingers to convince me that rounded rims are the way to go. More recently, I dropped a mesquite bowl with a knife edge rim. That edge didn't fare too well on the rough concrete street. Made me say naughty words.
     
  18. MichaelMouse

    MichaelMouse

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    You always do begin again unbalanced, because the average 1/4" diameter difference between the cross and long grain is going to be greater than anything beyond leaving the outside absolutely unturned. I bandsaw to better than that. I also re-turn stuff that has holes in it or wings on it with no additional problem that I can detect. You must have some OTHER kind of wood, or be in some kind of super hurry not to turn the full surface.

    That said, there were times when I didn't turn to round when roughing. Had an old Sears drillpress with 7 1/2" from center of bit to unmovable tube, and a lathe which would swing 15 3/4 (400mm). I just cut a 1/8 - 1/4" max depth flat on one endgrain portion to push against the tube to bore center. Since normal shrink pulled sides in and down about that distance, I never missed it.
     
  19. hockenbery

    hockenbery AAW Advisor Staff Member

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    MM,
    If you think it is easier to return rough surfaced dried bowls have at it.
    I find returning smooth surfaced dry bowls easier than returning rough surfaced dried bowls.
    It also allows removing less material.
    So I make my last passes with a bevel riding cut that leaves a smooth surface.

    You are most welcome to keep on turning rough surfaced bowls if that is what you prefer.

    If you balance the rim the for returning the bowl is not unbalanced just out of round.
    Two high spots equidistance from the head stock,, two low spots equidistance from the headstock.
    Easy to do with the bowl Jamed on a an open chuck.
    Your post in the bottom doesn't lend itself to balancing which is why you have unbalance returns.

    I made this statement in the my first post and you seemed to have gotten all wrapped up in refuting it.
    Again if you want to recommend leaving rough surfaces fine, I think it bad advice.
     
    Last edited: Apr 11, 2013
  20. robo hippy

    robo hippy

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    Rounding over the rims does make a difference. Dale Larson does it with long cylinders, I do it on all my bowls. Now, as to why it works, that I haven't really figured out yet. It could be in part because the sharp corner will dry faster because it is so fine, where if you round it over, it keeps things closer to 'even wall thickness', so the stresses will balance better. Not really sure, but it does make a measurable difference in drying success. The same goes for wrapping the rims of my once turned bowls with plastic stretch film.

    robo hippy
     
  21. 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.
     
  22. 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.
     
  23. 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.
     
  24. 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
  25. 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
     
  26. 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
  27. 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
     
  28. hockenbery

    hockenbery AAW Advisor Staff Member

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    Good luck with the fish!
     
    Last edited: Apr 12, 2013
  29. 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.
     
  30. 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.
     
  31. 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.
     
  32. 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
     
  33. 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.
     
  34. 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
     
  35. 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
  36. 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
     
  37. 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
  38. MichaelMouse

    MichaelMouse

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  39. 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
  40. 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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