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Thread: Bowed Cauls - Shop Made

  1. #1
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    Bowed Cauls - Shop Made

    You are probably familiar with the idea of bowed cauls. They allow you to place even pressure across a carcass surface where you would not ordinarily be able to get a clamp for glue ups. I made a couple 24" ones awhile back and find them useful for many things including the most touted benefit; reducing the number of clamps required to do a job.

    All that aside, I needed a couple more with a little more oomph so I thought I would share the process. I use some scrap material about as long as the caul will be. Make a mark to use as a reference for the midpoint of the caul's length. I use a shop made fairing stick to select my curve, draw a line from the mid point of the desired caul length to where the stop block will be. Sand to the line to create a template that is slightly more than half of your caul's length.

    I attach a support block for the rear edge and a stop block to register one end. The rear support is set back from the edge of the template the distance that will translate into your caul's height at the midpoint.

    The curve runs from what will be the midpoint of your caul length to the stop block position and beyond to allow a smooth transition of the pattern bit. Rough cut the caul blank to width but cut it precisely to length.

    Click image for larger version. 

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    Run the template from a little more than the halfway mark through one end of the caul to cut half the curve. Flip the blank and repeat for the other end.

    Click image for larger version. 

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    On these two I wanted about 1/8" of rise at each end over 24". The clamp is just snug enough to hold the caul still for the photo.

    Click image for larger version. 

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    Sorry for my photographic skillset (or lack thereof), you can sort of see the gaps at each end in the pic on the left and then I give each clamp a couple turns in the pic on the right. Surprisingly little clamping effort is required to bring it down tight and it really spreads the pressure out nicely.

    Click image for larger version. 

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    Last edited by glenn bradley; 11-05-2009 at 05:36 AM.
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  2. #2
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    Thanks Glenn! I was actually planning on asking the question "How do you make bowed cauls" within the next couple of days. Seriously.
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  3. #3
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    I have seen other methods like bending the blank in some sort of carrier and running it through the table saw as a rip cut. When the tension is released the bow presents itself in the relaxed blank. I went low-tech.
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  4. #4
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    I think I saw something one time about using a jointer to do it as well, something about lowering the outfeed table and keeping all pressure on the outfeed side. Your method just looks much more straightforward.

    What I'm looking forward to is using a set of cauls during the glue up phase on a table top to keep things flat.
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  5. #5
    I have a new way of making curved cauls.

    1. Make the blank for the caul then rip about 1" off the edge.
    2. Select a flat board longer than the caul add a stop to the front edge. (to be used as a sled for the planer)
    3. With double back tape fasten a 1/4" to 1/2" thick spacer at each end of the flat board that the strip from the caul will rest on. I also use double back tape to hold this strip to the spacer.
    4. Run this assembly thru your planer (take off small amounts) and the pressure from the hold down rollers will deflect the center of the caul strip and material will not be removed from the center only from the ends.
    5. Once you have the curve amount you are happy with glue this strip back on the rest of the caul and you will have a curved caul based on the deflection of the actual material.

    I actually do 2 to 4 at a time depending on how many I need.

  6. #6
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    What species of wood do you guys make your cauls out of?
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  7. #7
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    Whatever is in the scrap bin. My current ones are white OAK.
    "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

  8. #8
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    Do you think poplar would work, is it too soft?

    I've got a bunch of 8/4 maple coming (The shipper just called, he is still planning on sending the truck tonight ) so I'll probably use some of that. I'm sure I'll have some offcuts to use.
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  9. #9
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    Poplar would work just fine. I've heard some people have made em out of pine.
    "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

  10. #10
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    I'm not familiar with them, but I think they will solve some of my glue up problems.
    I love all the great idea's I'm learning here.
    Faith, Hope & Charity

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