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Thread: a bit confusing and 15 bf later

  1. #1
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    a bit confusing and 15 bf later

    I didnt want to come onto this end of the site and start with all the beginner questions. A few about chucks and lathes, but figured Id wing it from there.
    After alot, and I mean alot of attempts today and tonight at chucking up all size blocks and dowels, I finally figured I can get something cooking.
    I seem not to be able to rechuck a squared piece exactly, so I rounded over a square long piece.
    Then I cut out a simple knob and instead of doing anything to seperate on lathe, I decided to take out of chuck, and cut off with enough extra for mistakes.
    So I had the perfectly round piece, a knob cut out on one end, cut it off, made sure the cut was 90 degrees, and rechucked it with other end so I can dig out a little of the face of the knob.
    Problem is, it keeps coming out off center and I cant figure out why?
    Its the same size round piece, I purposely left an inch of same size to rechuck exact same way, and I cant carve out dead center.
    What am I doing wrong?
    I think I used 15 bf of spanish cedar today to get one knob which I havent gotten yet. I had alot of them crack off, one flew out of chuck.
    This is what I mean off center.
    Attached Thumbnails Attached Thumbnails wood stuff 1369 (Medium).jpg   wood stuff 1373 (Medium).jpg  
    Last edited by allen levine; 10-01-2009 at 12:15 AM.

  2. #2
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    Allen
    I haven't turned much but I can tell you from my metal lathe experance its very hard to re-chuck any thing and be concentric. You do everything you can with one chucking. And if you need to re-chuck you often improve things thing by re-chucking exactly as it was before.

    A four jaw chuck will let you recenter and I have seen these for wood.

    I suspect the woodturners will have much better advice.....

    Garry

  3. #3
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    Allen, I'm not sure what might be causing the problems you're seeing, but I wonder if it's how you're gripping the piece of wood in the chuck. Although it seems counter-intuitive, you don't want the wood to bottom out in the chuck jaws. Instead, you want the face of the jaws to be resting firmly on the should you have cut when cutting the tenon for the chuck. This sketch helps show what I'm talking about:

    Click image for larger version. 

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    Does this resemble what you're trying to do? If not, show a few pics of the piece on the lathe. That should help is troubleshoot the problem.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

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  4. #4
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    OK here goes, maybe this will help.

    Round the piece from end to end.

    On the end away from the chuck (this will be the bottom) turn a dovetail tennon, so the chuck has something to hold onto. Use your parting tool to identify where the bottom will eventually be, by making a shallow cut.

    Now, cut the blank off at the height you want the piece to be.

    Chuck up the tennoned end and adjust to run true.

    Turn the cup into the end.

    Sand and finish.

    Part off, angling towards the center so that the outer edges sit flat.

    That's the way I do it.

    Bruce
    Bruce Shiverdecker - Retired Starving Artist ( No longer a Part timer at Woodcraft, Peoria, Il.)

    "The great thing about turning is that all you have to do is remove what's not needed and you have something beautiful. Nature does the hard part!"

  5. #5
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    Vaughn, I was bottoming it out, but I was cutting it 90degrees on mitre first.
    Bruce, without cutting the dovetail I was chucking it, then figured Id just use an inch extra and cut off. but your way makes more sense.

    I think I discovered the problem with my approach.

    When first cutting round, I spun between centers.
    My mistake was I was using a fine point sharpie, since I cannot visually pinpoint the center with pencil, and just spinning spindles were fine like this.
    But rechucking it, off that tiny cm(mm) or 2, it then spun a bit off center from the original spot.
    I didnt realize how drastic any off center could result in rechucking it.(at least I think that was my problem)

    I got the solution, Bruces way seem easy enough once I gain the talent.

    IM sorry about the stupid question, I will search more and practice more before asking first grade questions.

  6. #6
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    Allen,
    Feel free to ask questions. We are all here to help and to learn.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  7. #7
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    Allen, you haven't asked a stupid question yet. I don't expect you ever will. We're all getting too old for this trial and error stuff. Take advantage of those who've of us already tried and erred.

    Quote Originally Posted by allen levine View Post
    Vaughn, I was bottoming it out, but I was cutting it 90degrees on mitre first...
    That still doesn't really work very well. The chuck gets a LOT of its holding strength and stability from the face of the jaws pressing against the shoulders. The gripping of the jaws is largely just to hold the shoulders to the face of the jaws, not to hold the tenon by squeezing it. Always leave a gap between the end of the tenon and the bottom of the chuck jaws. The only exception I can think of is if you're holding square stock. For me, in those cases I'm turning the whole piece with the tailstock in place, or I'm only holding it that way long enough to cut a tenon on the other end (and I still have the tailstock in place). If I want to hold the piece without a tailstock, I make sure I have a round tenon with a good shoulder.

    Bruce's suggested method will get you headed in the right direction. And keep in mind that pretty much any time you chuck or re-chuck a piece of wood, it'll need to be trued up, at least a little bit. (That's been my experience, anyway.)

    And to drive home a point a bit more, go re-read the first sentence in this post.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  8. #8
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    Allen, no dumb questions. In fact, I have chucked a few things on my lathe in my chuck. But still learned some new things from this post. Keep on asking, if you aren't asking you aren't using your lathe, then if that happens you might as well send it to Larry so it can collect dust on his workbench!!
    Jon

    God and family, the rest is icing on the cake. I'm so far behind, I think I'm in first place!

    Host of the 2015 FAMILY WOODWORKING GATHERING

  9. #9
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    My tip of the day

    If you think you are going to have to rechuck something mark the jaws and their placement on the wood. When you use a compression with a tenon the wood will be squeezed, probably different amounts by each jaw as it is never the exact same density all round so when it goes back in the tenon is misshapened. If you can put it back in where it came out in relationship to the jaws you should find it is far closer to centred.
    Another tip is to mark the centre of the wood if possible before taking out and use the tail to centre up before tightening the jaws when rechucking.

    Pete

  10. #10
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    thanx pete, I did that right away, marking it. I put a tiny piece of blue painters tape on the chuck, and made a pencil mark on the tenon so I could rechuck same spot.......today I went basically with Brians method, and everyone else who told me and realized after chucking I have to round over again, before I start any shaping. 3-4 hours yesterday, 3 hours this morning, I finally got 2 knobs, the most simple of simple knobs, but they are somewhat close, my daughter was home for lunch, said they are fine.
    Two dollars worth of store bought knobs, I spent a day and Im still off.
    IF I could have lifted the lathe, I would have thrown it.
    I started a collection of all the pieces of cutoffs and mistakes, I think its taking on the look of a chess set ready to be made.(maybe in 20 years from now when I know what Im doing)
    Im thinking Id be smart if I just bought three metal knobs for the inside drawers. At the rate Im going, it could be 8 weeks more.

    on a positive note, my scrap bin is finally seeing action and is empyting quickly.
    I also messed up the small gouge on the grinder today. I had the right angle set and everything, but I moved a bit, and lost the curve at the tip. The more I tried to get it back, the more damage I did.
    I see some kind of jig in my near future, or at least before I get any good chisels. It did cut like a razor though.
    Attached Thumbnails Attached Thumbnails wood stuff 1374 (Medium).jpg   wood stuff 1376 (Medium).jpg  
    Last edited by allen levine; 10-01-2009 at 05:31 PM.

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