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Thread: mounting green wood for end grain hollowing

  1. #1
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    mounting green wood for end grain hollowing

    What's the best way to mount a green workpiece for end-grain hollowing? I've tried faceplates, but the screws (1" machine screws) always pop out with the slightest catch or the general imbalance at the start of turning. Videos and my reference books don't seem to address mounting, just the hollowing.
    Thanks for any input.

  2. #2
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    I have always used a tenon and a steady rest once the form has been roughed out. What form are you planning on turning? Might make a difference as to how it is held.
    Steve

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  3. #3
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    I start with turning between centers. With big work I use the OneWay Big Bite. Then go to a tenon and chuck. 1" screws are very short, especially if you are using a welded faceplate. Not sure what a machine screw for wood is, but I use stainless steel sheet metal screws.

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    Richard thats the kind of screws I meant - sheet metal screws. One inch because that was a recommendation I read in a turning book, but not specifically for green wood. Steve, they're going to be some small bowls, maybe lidded boxes. Log is about 5.5" diam, so not much room for more. Once I get them roughed out and can turn a tenon, I know what to do, but its that initial roughing out part where I keep getting sudden failures. I assumed it was because the screws wont hold the wet end grain.

  5. #5
    Endgrain does not hold screws as well as side grain, so if using a faceplate longer screws are in order. I use the tailstock whenever possible for roughing. No reason not to turn between centers as Richard says.

  6. #6
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    Quote Originally Posted by Stan Calow View Post
    What's the best way to mount a green workpiece for end-grain hollowing? I've tried faceplates, but the screws (1" machine screws) always pop out with the slightest catch or the general imbalance at the start of turning. Videos and my reference books don't seem to address mounting, just the hollowing.
    Thanks for any input.
    What is the size of the work? Everyone I know uses a chuck for end grain work, in compression mode, meaning first turning a tenon. I (and I think most) do this by first mounting the wood between centers. Relatively small square blanks can be held directly in large enough jaws directly without turning a tenon but the grip is not as secure. Be careful to shape and size the tenon appropriately for the jaws.

    For their Powergrip jaws Teknatool recommends a maximum blank size of 8" diameter x 12" length. The Titan chuck with the Titan Powergrip jaws is rated for up to 14" diameter and 14" length.

    BTW, when tightening a chuck, especially one that has internal pinion gears, you can get a much better grip by repeatedly tightening in both of the chuck key sockets rather than just crank down in just one place. It's amazing how well this works. I heard a demonstrator once recommend "tighten the chuck in all six places."

    JKJ

  7. #7
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    Another tip is to bring up the tailstock during the roughing work.

  8. #8
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    I always start between centers, both because it is safer and because I can re-orient the piece as the grain starts to be revealed. I do almost all the exterior shaping between centers. Then I put a tenon on it and hold it in a chuck for hollowing. I use a big chuck (Vicmarc 150) with the largest jaws that will close on the piece-- the tenon is generally considerably larger than the finished dimension of the foot of the piece, but it holds very securely. (Haven't knocked one off the chuck since acquiring a hollowing rig and TV camera system). I haven't done anything deeper than a foot or so, so haven't had need of a steady rest yet.

  9. #9
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    Thanks everyone for input. I always do the roughing between centers, but have had trouble getting live centers to maintain a grip in green wood, thats why I was trying faceplates. I am only doing relatively small turnings on a midi lathe, so can go to a 4-jaw chuck when I get a tenon, just can't get past the roughing stage.

  10. #10
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    I use a marcantel drive for initial roughing, then use a four jaw chuck. The review posted here will explain how these work. They work quite well, and I don't know why there isn't more mention of them on the forum. This would hold green wood quite well, and not need the extra length for long screws.

    https://sawmillcreek.org/content.php...2s-Chuck-Plate

    Tom
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  11. #11
    I am guessing you were not using the tailstock when the faceplate screws pulled out, correct? A faceplate will work with long enough screws but there's no reason not to use the tailstock as well before hollowing. A spur center does give more adjustability when deciding on the blank's orientation. It's easy to spin out a small spur center when roughing- the larger diameter the better. The Oneway Big Bite Richard Coers mentioned is one good option. I am considering an Elio drive. https://woodturningtoolstore.com/pro...afe-drive-2-5/

  12. #12
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    Quote Originally Posted by Stan Calow View Post
    ... I've tried faceplates, but the screws (1" machine screws) always pop out with the slightest catch or the general imbalance at the start of turning...
    ... they're going to be some small bowls, maybe lidded boxes. Log is about 5.5" diam, so not much room for more. Once I get them roughed out and can turn a tenon, I know what to do, but its that initial roughing out part where I keep getting sudden failures. ...
    ... I always do the roughing between centers, but have had trouble getting live centers to maintain a grip in green wood,.... I am only doing relatively small turnings on a midi lathe, so can go to a 4-jaw chuck when I get a tenon, just can't get past the roughing stage.

    Stan,

    What kind of wood?
    What types of centers?
    What tool(s) are you using?

    It's difficult to know what to suggest without seeing you work. I hesitate to speculate on your tool technique but you really shouldn't be getting any significant catches. But if the piece is coming off the lathe due to imbalance that's a problem you should be able to fix.

    --Some ideas...
    If possible, make the blank as balanced as possible before mounting on the lathe. Some use a chainsaw to make the blank at least octagonal in shape before mounting. I generally use a bandsaw if it will handle the blank height (after squaring off the ends.) I like to lightly mount the wood between points of the centers and without turning on the lathe see how well it is balanced, adjusting the wood a little a time on one or both centers until it is balanced. Then tighten up the tailstock to mark the center points.

    Squaring off the ends can help a lot with the holding.

    If the wood is soft, driving a large spur center into the end with a hammer before mounting can provide better holding. If the end is not squared a spur drive center with just two spurs may be better than one with four, especially if the wood is hard. I always work with squared ends and prefer holding with steb drive and live centers. (I also almost always turn dry wood.)

    --As for catches, some general points (not to be taken as criticism of your tools or technique since I haven't seen you work!):
    Taking a big bite with a big tool can, of course, cause a big catch. A smaller diameter gouge can take a smaller bite. Smaller and more gentle cuts with a large gouge can work. The gouge, of course, should be razor sharp. (Using flat-topped carbide tools or scrapers to rough a blank can be a challenge.)

    There should be very little side force put on the blank when roughing. Cutting directly into the side of a rough blank can cause large side forces. Making roughing cuts more-or-less parallel to the lathe axis can be very gentle. This is especially important when face turning but also for end grain pieces, generally avoiding cutting "up hill" relative to the grain direction.
    I specifically do NOT recommend this idea if you are already having pieces come off the lathe but once that is solved: increasing the speed can make roughing smoother, assuming the blank is balanced. Not a safe technique with a large, heavy blank or one with cracks and voids!

    Again, without knowing more about your technique and experience I'm just guessing. Just curious, do you have expertise with spindle turning?

    It's difficult in this time of raging pandemic, but it might be very helpful to have another turner see your setup and watch you work. Even Facetime might work.


    BTW, when I turn lidded boxes from green wood I turn a cylinder with tenons on both ends, mount one end in the chuck, part off somewhere to make the blank for the lid, partially hollow first the body then the lid (leaving the walls thick), then set both pieces aside until they are well dried before continuing. When dry, I turn the box "most" of the way then let it sit, at least over night before finish turning - this lets stresses in the wood release and makes it easier to get a perfect fit on the lid. This is a common technique - I learned it from Richard Raffan. A end-grain bowl or hollow form or face turned bowl from green wood, of course, can be done in one sitting.

    JKJ

  13. #13
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    John Stated

    BTW, when tightening a chuck, especially one that has internal pinion gears, you can get a much better grip by repeatedly tightening in both of the chuck key sockets rather than just crank down in just one place. It's amazing how well this works. I heard a demonstrator once recommend "tighten the chuck in all six places.

    Stuart Batty advises a correct size tenon and a shoulder provide the best stability and to check the tightness of the grip of the jaws and retighten during the turning process Especially if you have broken off from turning example gone to lunch
    Axminster tools who manufacturer chucks have a video which echoes John's statement
    Last edited by Brian Deakin; 11-15-2020 at 5:51 AM.

  14. #14
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    Thanks guys. I know its hard to visualize. The problems I've had were when turning green sections of logs mounted on end, not typical cross grain bowl cuts. This has been in maple, ash, elm, redbud, and even basswood. These were sections about 6 inches long, 4-6" diameter. Its spindle turning, and I am just talking about during the roughing stage, trying to make smooth cylinders, (not even getting to the stage of cutting out the center. Turning on centers, the (Steb or 4-point) center to eventually start spinning a hole in the wet green end grain.Because the outside surface of the log is rough, there are tiny little catches (not blowouts) from the bark or surface irregularities, thus creating repeated small stresses on the contact points with the centers, eventually they spin free. I blamed this on the wetness of the end grain.

    So I thought mounting the log sections on a faceplate would be sturdier, again just for the initial roughing turning (with a live center on the tailstock). Again, after a while of roughing a log into a cylinder, the screws pull out of the wet wood and the piece falls off, not the typical explosion of the workpiece. I've used faceplates on dry wood all the time, so I'm comfortable with that. So I am inferring the problem is with wet, green endgrain, and, other than longer screws, if there's a better way to mount a log section. If my lathe were bigger, I'd just get bigger jaws.

    If its a technique issue, I'll accept that answer.
    Last edited by Stan Calow; 11-15-2020 at 10:27 AM.

  15. #15
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    Stan, with all respect, I think you have a different issue, unrelated to how you are holding the work. For pieces of log or quarters of tree trunks up to about 8" in diameter I use a drive like this one:
    one_saf_dri-2.jpg
    in my headstock. No teeth, no screws, no spurs. For bigger work I have a screw-on adapter for it from robust that makes a ~35mm circle. I've driven rough logs over 20" in diameter with that. I will occasionally get a catch that stops the piece spinning, but that is rare (and one of the big advantages of this type of drive). I think you probably have an issue with either sharpness of tools or how you are presenting them to the work or both.

    If at all possible I'd suggest you get together with an experienced mentor on Zoom or in person if conditions in your area make that sensible, to watch what you are doing and provide some coaching. You should not be routinely getting catches that would cause a spur center to slip or even 1" screws to pull out. Too heavy a cut, bad angle between the tool and wood, and dull tools can all contribute to that.

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