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Thread: Tear out problems turning a green birch log

  1. #1

    Tear out problems turning a green birch log

    Hi

    novice to green turning here. I have a few birch logs I got last fall and quickly sealed the ends. I cut one of them into blanks the other day and was turning this one yesterday. I keep having issues with "tear out" and not quite sure what to do. I don't know if this is caused by technique, bad wood, or just the kind of wood. I am using both a 1/2" and a 3/8" bowl gouge which I have just sharpened. The outside of the bowl was not too bad but the inside seemed to be much worse. The wood is we still for sure. I also tried using a bowl scraper on the inside where the tear out was but that did not seem to make any difference. Finally when I got it to shape for the drying phase, I just used my sander to get it smooth.

    I'd really appreciate your advice on what I might be doing wrong.

    thank you very much

    'mark



    IMG_5107.jpgIMG_5106.jpg

  2. #2
    Join Date
    Jan 2020
    Location
    Hoschton, Georgia
    Posts
    116
    For a twice turned bowl, end grain tear out is really not much to worry about when it comes to the initial turning. Just try to get the sides and bottom a consistent 10 percent of the diameter. The smoothness or surface tear out will all be addressed during the 2nd turning after the bowl dries.

  3. #3
    Ok, thanks for your reply and info.

    'mark

  4. #4
    I agree with Robert. I often find that when I prepare for a twice turned bowl I get a lot of tear out that is easily removed when I do the final turn. I never sand one I plan to twice turn . ..
    Pete


    * It's better to be a lion for a day than a sheep for life - Sister Elizabeth Kenny *
    I think this equates nicely to wood turning as well . . . . .

  5. #5
    Join Date
    Oct 2006
    Location
    Harvey, Michigan
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    20,593
    Mark, do you have any experienced turners near you? I ask because, in my opinion, the inside of the bowl looks to be more of a technique/tool presentation issue than that of poor wood. I agree that when twice turning bowls, the rough out does not need to be totally smooth but I always found that turning green wood was a fast and easy way to perfect my turning skills. Nothing more fun than watching those ribbons shoot up in the air while you slice the wood! Anyway, if you have a turner or turning club near you, get some hands-on advice and you will find turning green wood is a lot of fun!

    You did mention that you had just sharpened your gouges. If you can post a photo of what profiles you are using, that too may help determine the cause of the tear-out.
    Steve

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  6. #6
    I haven't turned much birch. So, one thing I will say is that a scraper, on bowls, generally doesn't leave a clean surface, other than on the bottom of a bowl where you are sweeping across flat grain. When you start to come up the sides of a bowl, tear out can get ugly because of the end grain that you cross twice each revolution. Getting a good finish cut for me is generally a shear scrape. I prefer a scraper with a burnished burr for this, and have one video dedicated to shear scraping. Some days the gouge works great, some days not... Okay, it is me actually. The shear scraping is a good way to smooth things out and get a clean cut. I also prefer to shear scrape the inside of the bowl in the transition and up the walls. I have found that some times I will get a better cut with a gouge that was sharpened on a 600 grit CBN wheel than I can with an 180 grit wheel, but most of the time the 180 is fine. Some use negative rake scrapers/NRSs. I still find that with most woods, they work like regular scrapers. Fine across the bottom of the bowl, but not as good going through the transition and up the walls. Generally a harder wood will cut cleaner than a softer wood. Another technique for removing tear out is to wet the wood, and I think some will spray sanding sealer on it. Then take very light passes. I had some Koa once and I had to wet the wood and take very light cuts several times to tame the tear out.

    robo hippy

  7. #7
    Tear out and that fuzz are two different things IMHO. When the wood is still green and softer, it won't cut as cleanly. Those end grain straws are pliable and can bend under the pressure of the tool; the tool takes off less wood than you want; Tear out is when the tool takes more wood than you want. In fact, some people have positive experience wetting areas of tear out to reduce it.

    Both problems are mitigated by better technique (tool presentation and lightness of touch) and a sharper edge. That being said, I wouldn't worry too much about it on the rough out. A lot of this will go away when it's dry.

    Another comment: your rim appears a tad thick relative to the walls. Beware of cracking; I'd also round over that inner edge.

  8. #8
    Join Date
    May 2005
    Location
    Northern MN
    Posts
    229
    I've turned a lot of paper birch, and some yellow birch (not sure which you have, or if you have another, river, red, etc.). I don't generally think of it as fuzzing badly like some woods, but there can also be some variation piece to piece, as well as variation with tool sharpness and presentation. My experience with green butternut is that it fuzzes horribly, to the point that the fibers cover the cutting edge and you have to clean them off to cut -- however, it cuts beautifully when dry.

    I would not worry too much over the fuzz and this point, though cutting it out can be good practice as others have said. The tearout near the bottom can happen as you push into endgrain and end up kind of twisting some fibers off rather than cutting them when you're traveling parallel to the grain. Just as an experiment, try resharpening then taking a very shallow pass and see if things clean up. Prashun also makes a good point about "fuzzing" being a different issue than tearout.

    Best,

    Dave

  9. #9
    Join Date
    May 2005
    Location
    Northern MN
    Posts
    229
    One other small hint on a topic you didn't ask about. When roughing a bowl that is shallow and has sides that are going more "out" than "up" at the edge, it's a good idea to leave the rough with a little bit of a vertical wall on the outside, instead of taking it all the way to a tapered edge. See pic below for visual about what I mean by a vertical wall. Two reasons. One, the thin edge will dry more quickly, and may encourage splits by doing so. Second, the bowl will change shape in drying; the side grain walls will drop relative to the end grain. Leaving the edge thicker vertically will allow you to lose less diameter when you do the final turning, because there's still a continuous circle of wood left. The fact that bowls don't shrink in long grain sometimes heads this off, as you have more length on the end grain walls, but it's still worth doing IMHO. This is particularly important when roughing out really shallow things like platters; you can get into a situation where the rough cups so much in drying that you can't get your plate out of it any more.

    Not that leaving this "vertical wall" doesn't apply if the bowl shape comes around more towards vertical on its own, in which case you don't have the same problem of losing the plane of the rim. Actually, the plane of the rim still moves (well, deforms), but it doesn't cause problems with final shaping.

    Understand I like the shape of your bowl for a final shape; I'm just suggesting that you leave a different shape in the rough out so you can get what you want out of the dried rough.

    Best,

    Dave

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  10. #10
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
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    1,403
    What grind do you have on your bowl gouges? What part of the tip are you using? Wile I wouldn't be too worried about it when turning a green blank I would use this to practice. The two biggest issues for me were gouging and tear out. Both come down to technique. If you don't have a club close by I would stick to using the bowl gouge, probably the 1/2" one. Try to learn how to use different parts of the edge of the gouge. If you haven't try to learn how to push , pull, and shear scraping with the bowl gouge.

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