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Thread: Day off and Tennon Problems

  1. #1
    Join Date
    Jul 2008
    Palm Springs, Ca

    Day off and Tennon Problems

    Well i got called off work today .....what a shame now ill just have to stay home and turn wood and work in the garage......LOL. Anyway i have an ongoing problem. When i turn my bowls the tennon breaks off very frequently. I have pictures at the bottom to show. The Tennon is about 7/8 in depth and fits into my spigot jaws on my chuck - i hollowed this one by leaving a tennon in the middle of the bowl and hollowed down to the depth i wanted. Then turned the tennon out of it....then with the scrapper showen i started to take shear cuts off the inside (freshly sharpened) and after in a short time the tennon broke off.........luckily i was on my last few cuts so ill be able to hot glue the pc back on and finish sand it.....
    Wondering what others think about why this keep happening or what i can do to make it more secure...........
    Im thinking that because its green wood (hemlock) that it probably stressed cracked when i was hollowing and didnt come apart because i have the tailstock up tight into the interior tennon i left on. Then after removal and still being green....and being far off the rest and deep hollowing it just cant take the stress even in light cuts..........

    Thoughts ?? thanks Dan
    Attached Thumbnails Attached Thumbnails Scrapper (600 x 450).jpg   Chuck (600 x 450).jpg   Tennon1 (600 x 450).jpg   Tennon2 (600 x 450).jpg   Tennon3 (600 x 450).jpg  

    Tennon4 (600 x 450).jpg  

  2. #2
    Join Date
    Jul 2008
    Hardinsburg, KY
    Dan, your tenon is too long. It should not bottom out on the bottom of your chuck. In fact, the top of the chuck jaws should register against the bottom of the bowl. Try it and see if it doesn't work better for you.

  3. #3
    Join Date
    Jul 2007
    Des Moines, IA
    Dan, I agree with Doug, the tenon is too long. Also if the tenon is about the size of the smallest opening of the chuck jaws, the jaws will grip better.

  4. #4

    Good tip.

    That is a good tip for us beginer turners. Thanks.

    Joe Penney

  5. #5
    Join Date
    Nov 2008
    Tampa & NC

    day off tennon problems

    Another thing that wasn't mentioned is that even though you are making a small bottom on your piece ,you don't have to have such a small tennon.You can do as allready said,but have a bigger tennon which will give you more wood for strength,then when you part it off you should be about an inch or so away from the tennon and can make the bottom as small as you like and that should end your troubles.

  6. #6
    Join Date
    Dec 2006
    Goodland, Kansas
    I agree the others. Make your tenon about 5/8" shorter and about a 1/2" larger in diameter. Your tenon is to long and way to small in diameter.
    Bernie W.

    Retirement: Thats when you return from work one day
    and say, Hi, Honey, Im home forever.

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

  7. #7
    hello, i prefer not to use tenon's for this type of work, i always use faceplates and create a waste block and part of above this.
    if you do ues a tenon you can strengthen it by using a couple of drops of CA or make them larger as has already been mentioned-but ideally avoid them.

  8. #8
    Join Date
    Jul 2008
    Alexandria, Virginia
    Thank you George.

  9. #9
    hello folks just to clarify any confusion i may have caused this is how i work to avoid snapping tenons.

    this is a piece of spalted beech 14" long by about 7" wide

    i start between centres

    i cut one end slightly concave for the faceplate

    i then mount my faceplate this one is 6" straight into end grain using sheet metal pan head self tapping screws about 1 3/4" long

    i wont bore you with the rest of these wip pic's and complete hijack this thread so we will skip along to the waste block bit

    in this pic the vase is complete except for sanding and you can see to the left is my waste block( but not always waste!!)

    sanded and oiled

    waste block shaped into a bowl

    i then used a 3"wide by 1/4" deep dovetail tenon to hollow it out and finally got rid of that tenon using a vacum chuck

    the days efforts

    a 3" tenon may strike some of you as excessive for such a samll bowl but splated beech isnt very strong and as i've already mentioned i prefer to have a large tenon if i'm going to use them. I do not know of any chuck jaws which would have given me such a strong hold on this vase- plus it doesnt help matters that i'm also clumsy and heavy handed so i need it to be strong

    hope this helped

    p.s i have quite a few wip pictures of various projects if you would like to see them???

  10. #10
    Join Date
    Jul 2008
    Alexandria, Virginia
    Quote Originally Posted by George Watkins View Post
    p.s i have quite a few wip pictures of various projects if you would like to see them???
    Yes please George. The nice thing about sharing is the ability of turners at all skill levels to interact, share, and gain knowledge.

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