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Thread: Tutorial: Shop Made Cauls

  1. #16
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    FWIW, I use Saran Wrap on my Cauls, and my clamps to keep glue from sticking to them.
    Jr.
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  2. #17

    Thanks

    Thanks for the info.

    Looked at your works and was awed. Great craftsmanship.

  3. #18
    Thank you Mike for a great write-up.

    I know I need to be respectful about advertising policy... but a few thoughts.

    Mike, when asked about tear-out you specify that soft-wood is forgiving...when trying to get pressure, these are 2 factors I typically don't want in the equation...soft and forgiving. But more importantly I think is this...

    The more accurately you can make them the more use-full they become.

    I would like to talk about the types of jobs you are using them for. I think most people when they think of cauls are refering to keeping boards aligned during glue-ups, but rarely beyond that.

    For example... would you trust yours to do this? Not saying it can't be done...but I've certainly never seen it. I'm pretty sure you're just buying more clamps. Expensive parallel jaw ones at that...



    Bowclamp "good caul"

  4. #19
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    Why don't you two just exchange a set of your respective cauls and each do side by side tests to prove each other wrong? The Great Caul-Off of 2010...East Coast v West Coast....Lets get ready to claaaaaaaaaaaammmmmmmmpppppp!

    Actually, I'm pretty serious.
    Last edited by Matt Meiser; 12-08-2009 at 9:42 AM.


  5. #20
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    Quote Originally Posted by Mike Henderson View Post
    Kent - how about some pictures of your setup. It would help to understand what you've done.
    Mike - here you go - sorry for the delay - camera was on vacation in Philly for a few days, but it eventually followed SWMBO back home.

    Simulated glue-up. Real thing has pipe clamps alternating over/under. Also, some type of screw clamp on the glue joint at the ends to pull the joint tight there. The "X" is flat - cauls taper from the "X" to the ends. I center the glue line on the "X" on the bottom cauls, and then use the wrap-around lines to align the top cauls - so the 2" flat spots are centered on the glue line. C-clamp and crank the ponies. Cello packing tape on the "X" caul surfaces. All I need is a card scraper or scraping plane to smooth the joint.

    Photo 001 shows the "U" fixtures nested - they stack real nice that way . The first version - I failed to allow enough room for the C-clamps to slip under the bottom caul - lesson learned - raised the "U" and pipe bracket height.

    FWIW - a section of wall has those PVC clips screwed in vertically-aligned pairs between studs - the pipe clamps snap into place and stay where I put 'em. Also - you'll see PVC clips that slide on the pipe - keeps pipe out of the glue.

    I need to do the "clamp on paper strips" trick noted in an earlier response. Mine seem to work great, but I could never think of how to check the curvature of the earth under clamp pressure - that is the way.
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  6. #21
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    Quote Originally Posted by Matt Meiser View Post
    Why don't you two just exchange a set of your respective cauls and each do side by side tests to prove each other wrong? The Great Caul-Off of 2010...East Coast v West Coast....Lets get ready to claaaaaaaaaaaammmmmmmmpppppp!

    Actually, I'm pretty serious.
    I want to make it very clear that I don't have anything at all against Craig's products. Neither do I assert that the particular shop made cauls I describe in my tutorial can do everything on the face of this earth, including changing the baby when needed.

    I was simply passing along a technique I was taught to make cauls, plus a few things I learned along the way. For what I do, my shop made cauls satisfy my needs - your mileage may differ.

    I will not be drawn into any type of contest between what I described and Craig's products. If you like Craig's products, buy 'em. If you want to make your own, my tutorial is one way to do it (and there may be better ways).

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  7. #22
    Please understand that the last thing I want is a competition either. I am the first to applaud Mike's effort...but as someone said earlier..."why would someone spend good money...?"

    I think it's fair to address that question. I also think it's fair to ask..

    What sort of jobs are you using your home-made versions for? And am I mistaken about their capabilities? And if so, how much time and money and effort did you put in, in order to get there? etc.

    Mike is completely right about this being the way our ancestors did it. But I bet they wished they had a CNC.

    Other small point of note... that flat spot in the middle... will bow backwards when you clamp the ends down, leaving a void.
    Bowclamp "good caul"

  8. #23
    Now that we have covered several methods of how to make cauls, can we discuss their design? for example is their a rule of thumb to determine how much bow they should have base on length or the like?

    I wan't to make some of these, but being the physics geek that I am, my mind keeps saying figure out how much bow the should have. Thus lets say I have some nice SYP all milled up that's 26" long by 3" tall, by 1-1/4" wide, how much bow Do I have to give the cauls?
    -Dan

  9. #24
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    Quote Originally Posted by Craig Feuerzeig View Post
    Other small point of note... that flat spot in the middle... will bow backwards when you clamp the ends down, leaving a void.
    Ummm.......if you notice the photo, you will see that I put the C-Clamps close to the edge of the panel, not way out on the end of the cauls (unless that's where the panel ends).

    And those "voids" you mention must be working pretty doggone good, since with this setup, for nearly 10 years, I have only had to use a card scraper to smooth the glue joint - never the thickness planer. Brings to mind Lincoln's reply when told Grant drank heavily - "In that case, find out what he's drinking, and send a case to each of my generals."

    You can certainly tell me you prefer a different design, but I don't understand how you can assert that mine doesn't work.

    My "project quality" has included dead-nuts repro pieces of Stickley/Ellis, with #1 bookmatched old-growth QSWO - pushing $18/BF from Talarico. I'm not building some paint-grade toy chest for a niece (I did that one without any cauls).

    I am so very happy you have a CNC, but I'm not inclined to apologize for my setup. I wasn't entering some kind of contest or argument, Craig - I was responding to Mike's request for photos. In the way-back-when, I would have jumped on Mike's tutorial, but I had to muddle my way through.

    And no - I'm not advertising anything because I'm not selling anything. Not my furniture. Not my cauls.

    Yeeeesh.
    When I started woodworking, I didn't know squat. I have progressed in 30 years - now I do know squat.

  10. #25
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    [This is in answer to Dan Sherman's question above]

    I don't think there's an easy answer to that question. Let me go into some discussion.

    The ideal curve is a cantenary. If all else if perfect, a cantenary curve will cause the caul to put the same pressure all along the surface. But there are some variables that affect your selection of the cantenary.

    For example, if your cantenary is too curved, you won't be able to pull the ends down. All of your pressure will be in the center and none on the ends. If your cantenary is not curved enough, you will not get even pressure along the surface - there will be a gradient of force along the surface with more on the ends and less in the center.

    So which cantenary should you choose. Well, that depends on the stiffness of your material, and with wood, that will vary from sample to sample.

    But all is not lost. For most caul applications just getting pressure along the caul surface is sufficient.

    A very good technique to get a cantenary curve is the one described by Wes Grass earlier in this thread.

    I don't worry about all the mathematics. I do a trial fit pulling the two cauls together face-to-face and see how much pressure I have to use on the clamps to get the cauls down. When I feel it's enough pressure, I then check the fit of the surface of the cauls to make sure the two faces are touching all along. If they are, I'm good to go. If not, I adjust the surface until they are, using Craig's paper test. I may or may not get perfectly even pressure along the faces, but it works for me.

    Mike

    [Let me add a bit about the cantenary curve. If your curve is too shallow, you can clamp them with equal force along the cauls, but you may not be satisfied with the force. That is, you'll have to put very light force on the ends to get even force along the cauls. If you make the cantenary too curved, but within the bending limits of the wood, you'll have to put a lot of force on the ends to get even force along the caul. So a perfect curve is only perfect for one amount of force on the ends.]
    Last edited by Mike Henderson; 12-08-2009 at 2:17 PM.
    Go into the world and do well. But more importantly, go into the world and do good.

  11. #26
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    Mike,

    What size are the Bessy clamps that you are using in the last set of pictures that you posted, are those 12"?

  12. #27
    Mike, I have an idea, but i will have to ponder it a little longer over lunch, I think we might be able to use the sagulator to calculate the bow.
    -Dan

  13. #28
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    Quote Originally Posted by Ben Martin View Post
    Mike,

    What size are the Bessy clamps that you are using in the last set of pictures that you posted, are those 12"?
    Yep, those are the 12" and I find that I use them quite a bit. When I first got them I thought they would be "special purpose" clamps but they're more like "general purpose" clamps for my use.

    Mike

    [Oops, I hope we're both referring to the same picture. Most of the pictures show the 12" and I think that's what you were referring to.]
    Last edited by Mike Henderson; 12-08-2009 at 2:03 PM.
    Go into the world and do well. But more importantly, go into the world and do good.

  14. #29
    Please don't let's debate the benefits of shopmade cauls vs cnc ones. That's been covered in other threads. Let's keep this one to a 'how to'.

  15. #30
    Quote Originally Posted by Kent A Bathurst View Post
    Ummm.......if you notice the photo, you will see that I put the C-Clamps close to the edge of the panel, not way out on the end of the cauls (unless that's where the panel ends).

    And those "voids" you mention must be working pretty doggone good, since with this setup, for nearly 10 years, I have only had to use a card scraper to smooth the glue joint - never the thickness planer. Brings to mind Lincoln's reply when told Grant drank heavily - "In that case, find out what he's drinking, and send a case to each of my generals."

    You can certainly tell me you prefer a different design, but I don't understand how you can assert that mine doesn't work.

    My "project quality" has included dead-nuts repro pieces of Stickley/Ellis, with #1 bookmatched old-growth QSWO - pushing $18/BF from Talarico. I'm not building some paint-grade toy chest for a niece (I did that one without any cauls).

    I am so very happy you have a CNC, but I'm not inclined to apologize for my setup. I wasn't entering some kind of contest or argument, Craig - I was responding to Mike's request for photos. In the way-back-when, I would have jumped on Mike's tutorial, but I had to muddle my way through.

    And no - I'm not advertising anything because I'm not selling anything. Not my furniture. Not my cauls.

    Yeeeesh.

    Kent I wasn't repying to your post or referencing it in any way. I'm sorry if you think I was. I happen to think it's a nice set-up. I was simply referring to the method of starting to plane 3-4" inches from the center... leaving a flat spot. I was just trying to give a pointer based on experience.

    And the whole point I'm trying to make is that of course it works for you, for the purpose intended. My question to nobody in particular is simply... Do you use them for other jobs around the shop? Do you use yours for veneer work? If you can get rid of those flat spots... maybe you can.
    Bowclamp "good caul"

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