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Thread: Through Mortise and Tusk Tennon

  1. #1
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    Question Through Mortise and Tusk Tennon

    This is my first post on this forum so let me start out by saying that I am mostly a power tool guy. I build, what I would consider, nice custom furniture for my house and friends. I have seen some truly amazing pieces of art on this and other sites that are amazing and I hope someday to be able to craft such things. My current project is a Mission Style Sofa Table. I decided to use this as an oppertunity to work on some of my hand tool skills. So I sharpened up my chisels, treated myself to a new corner chisel, and built a chisel mallet. (I was going to buy one but when I looked at it, I realized I could build the same thing for half the price)

    To my question: One of the joints I'm using is a Through Mortise and Tusk Tennon. I cheated alittle by using a router to plow out a majority of the waste material but then I used my chisels to shape the corners and trim the mortise to final size. My problem is the front side of the joint fits well but the back side looks sloppy and uneven. What is the best technique to keep this from happening? I sure this is a result from me not holding the chisel at a 90 angle when cutting. Any suggestions would be greatly appreciated.

    John

  2. #2
    First, are you scribing the outline of the mortise with a marking gauge & knife or using a pencil. If you are using a pencil, that is part of the problem. By scribing, you have a definate end point to register the edge of your chisel in for the final paring cut.

    Second, make sure your chisel is very sharp (you should be able to shave the hair off your arm with it) and take light cuts. Don't try to take too much material in a single cut or you will split more than you cut, resulting in a rough joint. Oak is hard stuff with coarse grain so it requires light cuts for a good surface. Also, touch up the edge of your chisel often during your work to keep it sharp. A dull tool does not leave a crisp edge.

    Third, cut only about half way through from each side and meet in the middle. Don't try to cut the entire mortise from one side or the side where the chisel exits will chip, split and otherwise blow out.

    Finally, If you are having trouble keeping the chisel vertical, you can clamp a guide block to the work to register the chisel against while you chop/pare. Of course you will have to continually move the guide block as you remove material but your mortise walls will be square.
    Bob

    "Whether you think you can or think you can't, you're right."

  3. #3
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    I lay out the mortise on both sides of the piece and work toward the center. This also helps to eliminate any tearout as you near the edge.
    "History is strewn with the wrecks of nations which have gained a little progressiveness at the cost of a great deal of hard manliness, and have thus prepared themselves for destruction as soon as the movements of the world gave a chance for it." -Walter Bagehot

  4. #4
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    Welcome to SMC. You'll find a lot of help here.

    I'll be interested in seeing some answers from more experienced guys here, but my initial thought is that I would lay out the through mortise on both surfaces, and cut from both surfaces to the middle.

  5. #5
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    Wow, thanks for the quick response. I have been on other sites before where I had to wait a week to get this many responses.

    I did use a pencil, tape measure, combination square, and hope to lay out my mortises. I put myself through college doing framing construction so these layout techniques are what I'm most comfortable with. Then I used the tennons I'd already cut to check my layout lines. When I was happy with them, I used a knife to scribe the cut lines, (I did this to cut the grain more than improve accuracy).

    I'm realizing that my question really should start with what is the proper way to lay out this joint and how do you transfer that layout to the opposite side of the work.

    Also what is the best way to "touch up" my new corner chisel? For my other chisels I used a combination water stone 1000/4000 I think and a jig that I bought to hold the chisel at the right angle for sharpening. Obviously this won't work for my corner chisel. Any thoughts?

  6. #6
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    OK, I've done some mortise and tenon work, but what is a "tusk tenon"?

    Welcome, John!
    Veni Vidi Vendi Vente! I came, I saw, I bought a large coffee!

  7. #7
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    [quote=Brian Kent;818619]OK, I've done some mortise and tenon work, but what is a "tusk tenon"?

    Tusk tenon - a kind of mortise and tenon joint that uses a wedge-shaped key to hold the joint together


  8. #8
    Quote Originally Posted by John Pahl View Post
    I did use a pencil, tape measure, combination square, and hope to lay out my mortises. I put myself through college doing framing construction so these layout techniques are what I'm most comfortable with. Then I used the tennons I'd already cut to check my layout lines. When I was happy with them, I used a knife to scribe the cut lines, (I did this to cut the grain more than improve accuracy).

    I'm realizing that my question really should start with what is the proper way to lay out this joint and how do you transfer that layout to the opposite side of the work.
    First make sure your stock is straight and square, which I'm assuming you already did with your jointer and planer. Then pick one face and one edge and mark them as reference faces as shown here.



    From here on out, register your square or marking gauge only off one of these two references, this will ensure the most accuracy. Layout the position and height of the mortise on the first side, then transfer the position and height around to the other side with your square. Use a knife, not a pencil. Use a marking or mortise gauge to transfer the width of the mortise to both sides, registering the gauge's stock off the same reference face each time you scribe, similar to this.


    Voila, you have a perfectly aligned mortise layed out on both faces. Now just don't go past your layout lines .
    Bob

    "Whether you think you can or think you can't, you're right."

  9. #9
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    ditto what Robert said...

    Get yourself a mortise gauge, they are vastly superior to measuring and marking by pencil.
    "History is strewn with the wrecks of nations which have gained a little progressiveness at the cost of a great deal of hard manliness, and have thus prepared themselves for destruction as soon as the movements of the world gave a chance for it." -Walter Bagehot

  10. #10
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    Thanks for all the detail. I will be heading back into my Shop ASAP to try this out. I will need to remake the pieces I screwed up but that shouldn't take too long. I will also be looking into a marking guage.

  11. #11
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    Got it. Thanks John.
    Veni Vidi Vendi Vente! I came, I saw, I bought a large coffee!

  12. #12
    Ah....work both sides towards the middle....I'm now confident the next set of through mortises will be MUCH nicer

    No time to redo the ones I made last week because xmas is just around the corner, but the roughness around the edges has been bothering me. It still looks decent...but not nearly as crisp as I'd like.

  13. #13
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    If you don't have a mortise gauge handy and regular marking guage can work as well, preferably two set at different measurements. But you could just change the one marking guage after all the marks for the first measurement are done then go on to the next, a bit more difficult and requires you to look ahead a bit more.

    The biggest difference in what my steps are between yours is that I always cut my mortises first! Then I size my tenons to fit the mortise. Shaving off the faces of tenons that are oversized is much easier for me than cutting the mortise walls to size. And accurate layout with a marking knife is imperitive! Bringing a line from one face to another is most accurately done with a knife, no comparison to a pencil mark.

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