Natural Edge Bowl Bottoms

Discussion in 'Newbie' started by loberg, Apr 26, 2009.

  1. loberg

    loberg

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    I turned my first natural edged bowl last night. I shaped the outside, formed a tenon and shaped the inside. This morning I realized I cannot chuck up the face of the bowl and turn the bottom. I have in the past used a tennis ball as a holder (with the tail stock, of course) but the bowl is too big for that to work. Any hints on how to finish the bottom? I have tried to look on You Tube but found nothing relative. The piece is bay and turned nicely.
     
  2. Bob Edwards

    Bob Edwards

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    reverse chuck to address the bottom

    You have not mentioned the size if the bowl but the average for me is anywhere from 4†to 8†across and a max of 7†deep. I have made a number of aids to use for the purpose of finishing the bottom. Basically they are round forms with a tenon to fit the jaws of my chuck and long enough to reach to the bottom of the bowl. They vary in diameter from 2†to 4â€. The end that touches the bottom of the bowl is slightly convex and I have glued a piece of scrap split lather to the face. The trick to using this method is to start the project between centers. There are several advantages to doing this. You can tweak the axes so the high and low points of the edge will appear at the same point, or not if you prefer. When you have turned the tenon and are ready to reverse the bowl and put it in the chuck it is most important that you not destroy the mark made by the live center on what will be the bottom. After you finish the hollowing and reverse the bowl into the leather covered “drive post†the original mark of the live center will be available to find the center of the bottom and insure the bowl will turn true to the original axes. You can then cut off the tenon and shape the bottom leaving a nub about 1/8 to 3/16 in dia. And just proud of the service. You leave it proud and sand it off because if you try and break it or cut it off flush it will most likely tear out and leave a hole. This is long but I hope it helps.
     
  3. John Boyles

    John Boyles

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    Natural Edge Bowl Bottom

    You may be able to mount a cylindrical peice of wood in your scroll chuck and turn a profile on the tailstock end of that peice that will fit against the inside bottom of your natural edge bowl. The length and diameter of the cylindrical peice of wood depends on the diameter and depth of your bowl. The idea is to mount your bowl with the inside against the peice of wood in your scroll chuck the bring up the tail stock and place the tip if the live center against the exact center of the outside bottom of the bowl. Being a natural edge bowl, you made need to make small adjustments to make your bowl turn true after you have it mounted between centers. You can place a paper-towel or peice of cloth between the inside of the bowl and your jam chuck to keep from scratching the insife of your bowl. I realize that this method will leave a small part in the exact center of the bottom of your bowl that may need to be sanded by hand but that is not so bad
     
  4. loberg

    loberg

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    Wow. That was an idea I had not thought of. I was going to use a kid's play ball to chuck up the bowl but your method is better. The bowl is about 4 inches in diameter and about 4 inches deep. As soon as I figure out the digital camera I will try to post pictures. The bowl came out with the bark still attached and looks good. Thanks.
     
  5. drh

    drh

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    You might also try the straka chuck (donut chuck).
    http://www.alanlacer.com/articles/StrakaChuck.pdf
    I made one up and use it all the time for standard rim and natural edge bowls. I use a 4" pipe on natural edge bowls, in your case, 3" would work better. If you leave the tailstock dimple in your tenon, it's real easy to line up the bowl bottom, turn the tenon off with the tail stock in place, then remove the tail stock to take the final center part off (light cuts). Without the tailstock in place, you can then get fancy with the bottom if you choose. I cut the grooves in my plywood disk as described in the article, but it's not necessary as long as you leave the tail stock dimple on your tenon. (I never bother using the grooves to line up my bowls and so would not bother with the grooves)
     
  6. loberg

    loberg

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    I used the drive post method Bob suggested. It worked excellent. I am making a donut chuck for future use and larger pieces. I finished the bottom by putting the 2" sander in a drill press and sanded out the inperfections. Thanks a bunch, I learned a lot.
     
  7. MichaelMouse

    MichaelMouse

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    You could just refuse to play such games and do things up prior to reversing to hollow. That way you let things dry, run your block plane or block-backed sandpaper across the bottom to take off the high center, and call it good.

    http://i35.photobucket.com/albums/d160/GoodOnesGone/Bark-up.jpg

    Haven't found (m)any folks who worry about the slight oval shape of the recess. The bowl looks oval anyway.
     
  8. LHauch

    LHauch

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    Hi,

    I've used both jam and vacuum chucks for finishing the bottoms. If I use the jam chuck (with the tailstock) I will try to get down to 1/8" dia. on the nub, then use a small power (reciprocating) carver to remove the nub (Jimmy Clewes demos this on one of his DVDs) then sand down what's left. Bill Grumbine's DVD shows him using a wood carver's gouge (looks like a #3 sweep spoon gouge.)
    I even use a jam chuck for vases (I made one yesterday from a 4x4 about 14" long.)
    If you decide on the vacuum chucking method, be sure to add a regulator valve to limit the air flow, otherwise you may break a very thin wall bowl.

    Not sure what type of lathe you have, but you can get set to do the vacuum chucking any where from $100 (my Nova) to $400 or more.

    Cheers,
     
  9. odie

    odie

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    Here's an article by Bill Grumbine describing his compression chuck. This can be easily adapted for use with natural edge bowls, and I thought it would be appropriate to add a link to in on this thread......

    http://www.woodcentral.com/bparticles/jamb_chuck.shtml

    ooc
     
  10. john lucas

    john lucas

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    Go to this link and click on the tips section. I have an article on revers chucking bowls. You should be able to find a method that will work.
    www.cumberlandwoodturners.com
     
  11. Joe Greiner

    Joe Greiner

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    Although it won't work for a bowl that small, I've used short pieces of newsprint core for center positioning jam chucks for NE bowls. The cores have very precise standard dimensions, and can be mounted in expansion mode on a scroll chuck. Turn the free end to match the bowl inside slope at that diameter; cushion as needed. For the initial squaring cut, I wrap some wide adding-machine tape secured by masking tape, and cut to its edge with a hacksaw or backsaw.

    While tightening the tailstock end of the mount, wiggle the workpiece around to assure it's concentric (or not, if you like). The last nub of the bottom cut can be just sliced off afterwards. And there's no restriction on the method of mounting (socket or tenon) for the hollowing cuts.

    Unfortunately, this is also a very good way to make funnels.:eek:
     
  12. S. Clark

    S. Clark

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    I just got a kick out of the “power†tool being used. Myself, I’m a man and use a hand saw!

    - Scott
     
  13. loberg

    loberg

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    I'm building a donut chuck. I found an aluminum chuck that is "extra" and will use it to anchor the donut chuck. I found circle plywood at the local hardware store and will use those. All of your suggestions are great and gave me very good ideas.

    Woodturner Catalog now has a bowl chucker pad for sale (pg 39). I am thinking of buying one ($15.99).
     

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