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Thread: HF question

  1. #1
    Join Date
    May 2008
    Location
    Kansas City, MO
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    151

    HF question

    I have a question for you Hollow Form guys.

    Having not done any hollow forms yet, I would like to know how you creekers block out your green wood to dry for later finish turning.

    Do you hollow the interior, leaving a heavy wall? Do you just drill out the starter hole and hollow later? When you wrap in paper to dry, do you put sawdust or paper inside?

    I have made my own Jamieson style boring bar and am working on an Elbo style holding rig. I am trying to get my ducks in a row to start hollowing. I have a couple of Black Walnut logs that need to be worked over before it gets too cold out in the shop.

    Thanks for your help,

    Chris Colman
    Quando Omni Flunkus - Moritatem!

  2. #2
    Chris, all of my hollowing has been done on dry wood. However, having seen several on here rough turn them green, I do have one "in the making." It should be ready to finish turn by now.

    The suggestions to me were to turn them on the 10% rule, hollowed to approximately 10% thickness in the walls. My form is a little over 6", so I left about 1/2" thick walls, wrapped it in 3-4 sheets of newspaper, taped it up, opened up the entry hole, and laid it on a shelf to dry - some say upside down. Several creekers also use kitty litter to pour inside to soak up the moisture.

    Hopefully, my piece will finish out properly - time will tell!! I am sure you will get some more input on your question from more experienced folks!

  3. #3
    Join Date
    Oct 2006
    Location
    Harvey, Michigan
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    20,801
    Chris - I turn my HFs to 10% thickness (usually 5/8" to 3/4"), soak in denatured alcohol (DNA) and then wrap with brown paper bag with the paper punctured so that air can get to the interior of the form. The idea being to control the rate of drying so that the interior dries slightly faster than the exterior.

    Another thing to do is round over any sharp edges - such as on the lip of the opening - because the wood will dry out on the edge before anywhere else and possibly start cracking at that point. Simply rounding the edge over helps prevent that from happening.

    One thing to pay attention to when hollowing is to make sure the wall thickness is equal - no matter how thick you leave it. If one section - say the shoulder area - is twice as thick as the adjoining walls - the form will crack. Equal wall thickness means equal drying time/equal stress to the walls.

    Have fun! Looking forward to seeing your first hollow form!
    Steve

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  4. #4

    I'm the crazy Uncle

    MOST of the time, I hollow to finished dimensions, sanding the outside to at least 400 before I go inside. Crotch HFs are expected to distort, I like the lumps and bumps that form over a fairly short time as the wood takes its "final" shape."

    Burl material I sometimes turn twice so that I can get a smooth surface. Then, I like to use the 10% rule. If there are voids, more like 15/25%, just in case there is a lot of movement in those areas.
    Voids tempt me to turn to finish and just see what happens.
    I have stopped at just doing the form and drilling to depth leaving the rest for later, but so far, never really "long enough" to get really dry wood at the end (unless it gets stored someplace and uncovered MUCH later).

    As I have said, I like texture, but with really CURLY wood, I use the 10% rule then let it DRY. Curl seems better to me when you can't actually feel it.

    When I turn a "plain ole piece of wood" I usually turn to finish. It may move some, as to shape but the surfaces seem to stay nice and smooth.

    Sometimes, I think the gloss finish I occasionally use, even on green pieces helps protect the outside from cracking... Which, I hate to say, almost never happens to me and the MOST I do is stick some of the pieces in fresh shavings for a few days then move it to a banana box with other stuff to finish later. I tend to leave sharp edges, I know it's bad, and as soon as I "pay" with damage to a favorite piece, I'm sure I'll stop doing that too, but for now its :life on the edge."

    I just did a couple of pieces, with some fairly major voids in black locust burl. I turned them to finish. The first one dried NICELY while the second one was waiting to get turned. Because the first/smaller one came out so well, I turned the second one to finish also. This particular burl seems to have little shrinkage or distortion as it dries. The surfaces stayed about 85/98% original/smooth and shiny.

    So far, for me, it all seems to work. And, it depends on the wood.
    Change One Thing

  5. #5
    Join Date
    Jan 2005
    Location
    Goodland, Kansas
    Posts
    22,605
    Most of my HF's are turned to finish. I turn them mostly to 3/8" or maybe slightly less. I soak them with the first coat of Antique Oil till they won't take anymore. I just keep adding it till the whole surface is flooded with oil. I let them sit for 10 minutes or so and wipe of the excess. So far haven't had on crack on me. Some will distort a little but not to much.
    Bernie

    Never put off until tomorrow what you can do the day after tomorrow.

    To succeed in life, you need three things: a wishbone, a backbone and a funnybone.



  6. #6
    Join Date
    Feb 2003
    Location
    Green Valley, Az.
    Posts
    1,202
    It's been a long time since I've finished turned a wet piece of wood. I don't want any distorted pieces if I'm to add a collar. My system is simple. I rough turn to about 10 percent if it's a wood that will warp a lot. Otherwise, a bit less than 10 percent. Then I merely heavily wax the outside with Johnson's paste wax. I mean slather it on. It then goes on a shelf to dry. I put a date on it and in 6 months or less it's ready to turn. I buy my wax in cases of 6 direct from Johnson.

    I've never seen a need to bother with newpapers, DNA and all the other methods. If a piece is very wet and is a wood that's prone to crack I wax it and brown paper bag it for a few weeks.

    I'll add that I live in hot, dry Arizona and I never have a cracking problem. Right now I have 50 or 60 rough turned pieces waiting to be re-turned. None are cracked. I've been using this method sucessfully for at least 30 years.

    A little tip that I got from the old Master Rude Osolnik. To see if a piece of wood is dry hold it against your cheek. If it's cold it's still wet. If it's warm it's dry. Seems to work.

    Wally
    Last edited by Wally Dickerman; 12-04-2010 at 12:13 PM.

  7. #7
    Join Date
    Jan 2008
    Location
    Bangor, PA
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    1,853
    George,
    How do you avoid having the sandpaper clog when you sand a green from. Do you wet sand or use something special? Then do you finish immediately?

    Bernie,
    You mentioned oiling the outside of the HF. What do you do to the inside and when>
    faust

  8. #8
    Chris,

    try several different methods, see what you like best

    i turn to finish thickness, that means that i hollow 2 inches at a time to final thickness, then do the next 2 inches to final thickness

    i usually sand before hollowing

    i put newspaper inside the hollow form for a couple of days to slow the inside drying

    one of the reasons i do hf instead of bowls is that hfs have less warpage than bowls, i do not have 100 bowls waiting to be finished turned

    the shpae of the hf will tend to hold the vase form, the sanding will dry the hf, if the piece is extremely wet above 30% moisture reading i will bag it and put newspaper inside

    do not put finish on till the piece has lightened in weight, hold the piece in hand after finishing, hold it again several days later, you can feel the differance, and the weight loss is all because the wood has dried

    try several mehtods, remember there is no such word as always
    Last edited by charlie knighton; 12-04-2010 at 12:04 PM.

  9. #9
    Quote Originally Posted by Faust M. Ruggiero View Post
    George,
    How do you avoid having the sandpaper clog when you sand a green from. Do you wet sand or use something special? Then do you finish immediately?

    Bernie,
    You mentioned oiling the outside of the HF. What do you do to the inside and when>
    faust
    Faust,
    I generally power sand with Kukui nut oil or mineral oil, keeping it kind of wet till 220/280, then I use the oil that has soaked in to do the higher grits. I also use a reversing drill. Reversing directions loosens the impacted stuff, at least for a while. When all else fails, I spray a little DNA on the sanding disk and just wipe off the stuck in/on stuff.
    Much of the time, I finish with a microcrystaline wax stick and just burnish it back with a paper towel. The wax doesn't take fingerprints much. It's better than bee's wax in that regard (which I used to use).
    When I apply the VanAqua water based poly, it is right over the freshly sanded piece. No alcohol or anything. I checked with the manufacturer and they suggested a "tape test." Apply finish when dry to touch, apply scotch tape. When the finish is DRY remove the tape. If the finish lifts, it will probably come off at some point, at least in places. If it stays (and this did) it will STAY.
    Change One Thing

  10. #10
    Join Date
    May 2008
    Location
    Kansas City, MO
    Posts
    151
    John,

    I am not sure I understand the 10% rule.

    Do you mean by 10% that the wall thickness should be approximately 10% or the form's height?
    Quando Omni Flunkus - Moritatem!

  11. #11
    Join Date
    Feb 2003
    Location
    Green Valley, Az.
    Posts
    1,202
    Quote Originally Posted by Chris Colman View Post
    John,

    I am not sure I understand the 10% rule.

    Do you mean by 10% that the wall thickness should be approximately 10% or the form's height?
    Wall thickness is 10% of the dia. of the piece. 10 inch piece, 1 inch walls. I usually go a bit thinner unless I expect a lot of warping.

    HF's tend to warp less than open bowls.

    Wally
    Last edited by Wally Dickerman; 12-04-2010 at 5:11 PM.

  12. #12
    When I read that one guy slows the drying on the INSIDE by stuffing newpaper in there, and another guy wraps the paper on the OUTSIDE so the inside dries faster, you then know why I ask advice from all but don't take it for gospel. I woulld suggest doing it your own way and take any suggestions with a bit of healthy skepticism and a grain of salt!

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