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Collet type wooden chuck jaws

Discussion in 'Tutorials and Tips' started by Don Wattenhofer, Nov 16, 2020.

  1. Don Wattenhofer

    Don Wattenhofer

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    Location (City & State):
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    1. DSC00782.JPG This collet chuck is made from 1 solid piece of wood with a dovetail tenon to mount in a scroll cuck. The procedure to make one is turn round between centers and form the dove tail tenon at the optimal diameter for your chuck. Next mount in your chuck and bore a 3/4 to 1" hole all the way through to allow finials to extend back into the spindle bore. Next determine the form you will be gripping and turn the inside accordingly (for globes similar to the one shown the large diameter should be slightly back from the leading edge to positively grip the piece). The saw cuts can be made by setting a flat top tool rest near center, then with the indexing pin in place use a stiff back saw sliding on the tool rest to make the cuts. ( to get 8 segments equals 4 cuts on 4 index positions). The final step is to add the hose clamp and tape down the tail. The disadvantage of this type is that the work piece will be pulled slightly off center when the hose clamp is tightened.
    2. DSC00792.JPG This collet chuck will use the self centering features of your scroll chuck. The optimal diameter of the dovetail tenon on my chuck is 4.06" (4 1/16th") so I cut a 37" long piece of white oak to 2 1/4" square then cut it in half and glued side to side with craft paper between and when that was set up cut it in half again then glued the halves together being sure that the glue lines/paper meet in the center. The resulting 4 1/2" square block is then mounted between centers with the junction of the 4 pieces as the center point and turned round to about 4 3/8" diameter. The dove tail tenon is carefully cut such that the bottom or end nearest the head stock is in full contact with the jaws as is the outer edge of the jaws ( this is necessary because the wood jaws will be bolted thru the steel jaws). The entire block is then mounted in the scroll chuck, marked for the desired length then parted off and squared off. The next step is to bore the center out and cut the internal form as required. The next step is to remove the piece form the chuck and one steel jaw to use as a boring guide to bore the holes for the mounting bolts. The steel jaw should be positioned on the dove tail end so that the seams are equal distance from each edge then using a drill press and a 15/64th drill bit bore the holes and repeat on all 4 segments. The outer ring cap screws could go all of the way thru or counter bored as I did and it should be obvious that the original flat head screws will not work. The jaws can easily be separated then cleaned up / trimmed on a disk sander. The inside contour can be changed if needed by installing the wood worm screw and tightening the jaws.
    3. DSC00795.JPG
     
  2. Timothy Allen

    Timothy Allen

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    Don, did you give any thought to the grain orientation in the wood chuck jaws? It looks like you've got two that are "plain sawn" (as it were) and two that are "quarter sawn," and I wonder if it makes any difference...?

    Also it sounds like your wood jaws are mounted over top of your steel dovetail jaws, with screws that go through both the wood jaws and the steel jaws to get to the base jaws in the chuck? Is that correct? Is there a reason for that, or could one mount the wood jaws directly to the base jaws in the chuck? I guess maybe it might be difficult to create the appropriate "key" for the wood jaws to mesh with the base jaws. I know Oneway makes "flat jaws" for their chucks for the purpose of mounting wooden top jaws...
     
  3. Don Wattenhofer

    Don Wattenhofer

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    I looked at the flat jaws and could not see a reasonably stable method to attach wood to them for the collet size I want to have. The sandwiching of the steel jaws seams to be the most secure plus I don't have a set of flat jaws. The thread size for the base jaws is M6-.75 I believe but I can't find any long cap screws in that size so I am considering buying a die and make my own out of rethreaded 1/4" cap screws.
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Are you sure that the thread pitch is 0.75 mm and not 1.0 mm? I think that cap screws are often hardened so rethreading could be a problem.
     
  5. RichColvin

    RichColvin

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    Don,

    Consider moving the hose clamp back toward the chuck some. I take a similar approach when turning certain pieces on my rose engine lathe, and I consider the wooden collet chuck to be expendable.

    The picture below has a yellow heart piece, held in an ash chuck.

    51D96F5A-8B51-4E1E-B1B6-815580FF1CC3.jpeg

    Kind regards,
    Rich
     
  6. Don Wattenhofer

    Don Wattenhofer

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    You are right I found someone near me that has a metric tap & die set and one of the original cap screws screwed into a M6-1.0 die plus the 1.0 pitch gauge fit perfectly. The rethreading idea was to use the unthreaded part of a 1/4" hex head cap screw turn it down to 6 MM and thread it for M6-.75 but that is no longer necessary. The reason for the longer cap screw is that after writing the description I realized that a longer screw would be a better way to attach it than the shorter screw and counterbore.
     
  7. Don Wattenhofer

    Don Wattenhofer

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    Location (City & State):
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    The picture you have included does not show a hose clamp.
     
  8. Don Wattenhofer

    Don Wattenhofer

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    Location (City & State):
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    woodJawsend.jpg This is the more refined example using 80 MM long M6-1.0 Philips head machine screws (that is the only 80 MM screws I could find) as shown on the outer ring and 40 MM long on the inner ring. The standard dove tail jaws are sandwiched in between the wood jaws and the scroll slides. The wood jaws did not show any deflection when tightened around the ornament globe and the globe ran true.
     

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