Friday, February 12, 2010

Tréteau XXII

Post 22 in this build of a 19th century French sawhorse- previous posts archived to the right of the page.

On now with the tenons, tenons, and more tenons. I started working on the short side brace pairs first, and the easiest to cut were the tenons meeting leg BN, as it is rotated to be normal to the short axis of the plan. After the preliminary saw cuts, I used my router to define the thickness of the tenon, then lopped off the end:


Next, I trimmed it to its tapered form:


Cleaned up, with exception of the tenon shoulders which will be kerfed to the leg:


The next one was a bit trickier, as it connects to the corner of the faces aplomb leg AO. I roughed out the angled cuts using my circular saw to make a series of kerfs across the face, chopped the waste out and then decked the surfaces as far in as possible (which wasn't very far) using the router. Then I trimmed the end of the tenon:


A while later:


The bottom of the tenon, which is admittedly ridiculously small, oddly shaped and simply inconvenient to cut, needed to have a 90˚ abutment, so I got out my azebiki to make that cut:


Then trimmed the other way using a flush cut saw:


The result:


Onto the the next tenon, which connects to the upper side of leg AO:


Sawing for teens continues:


Finished form of that tenon:


And last is the tenon which connects to the lower end of leg BN:


I cleaned that up a bit and then proceeded to try the fit:


A while later, after several rounds of kerfing and paring, I had the first of the short side brace pairs fitted, more or less, to the legs:


Another view:


I'd show more pictures, but that's the 15 for today. The fit is decent, and the tenons are snug in their mortises, though there is some light around the shoulders of one of the connections at leg AO, which I hope will come out with a little more fiddling. With so many joints coming together at once, and given the splayed form, one has to think carefully about any adjustments to fit, as each change has a cascade of effects.

That's eight tenons down, sixteen to go.

Observation: the lower ends of the braces, fitting as they do into blind mortises, really aren't doing a whole lot. They would be fine for a roof assembly in which the bottoms of the hip rafters would presumably be contained from spreading by some sort of tie beam (or a buttressed wall, say), but in the case of a splayed-leg sawhorse, they need to act to restrain the legs from spreading, and they are not capable of that - even if they were, it would be tension connection, which is a poor choice anyhow. I can't foxtail wedge them due to the unfavorable grain angle and tenon shape in this case. I am debating whether to glue them, or to fasten them through to the legs using a timber screw, and I'm leaning towards using the timber screws. Another option would be some sort of cross-wise wooden draw bar through each lower connection with opposing wedging pins, but that seems a bit ridiculous and would probably be vulnerable to damage. I'll think a little more on this as I continue the cut out. Learning lots as I go.

I remember when I first made a Japanese style splayed leg sawhorse 10 years or so back there were some pretty critical details which I did not grasp and yet the sawhorse went together (albeit poorly and definitely not in the way I thought it was supposed to come out). Making the thing is the key to understanding - despite all the drawing work, and benefits of 3D visualization, it is not until the wood gets cut and fitted does the picture become crystal clear. I have lessons to bring forward from this into the next piece, and that is a victory in and of itself.

Thank you for dropping by, and welcome to the new followers who have signed up in past days.

3 comments:

  1. Great post Chris. My joinery skills have improved a great deal since I've been following your blog. You bring to life what I've only viewed in books. Any possibility of videos in the future?

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  2. woah....i think you are truely insane. those joints are out of this world!

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  3. Dale,

    hey thanks. Now, videos are one area I haven't explored, though it has crossed my mind. I'm a bit mortified to watch myself on video - that's one problem. There is no denying that I live in a culture where the vast majority are strongly conditioned and attuned to the video image, so going that route would be a good way to get stuff out there in to the, uh, stream of consciousness.

    Nick,

    yes, pretty much insane here, with no desire to return to 'normal' anytime soon!

    Glad you like the joints, though personally I would do several of them differently the next time. This sawhorse has been a real mind bender, and the compound joinery cutting is proving to be a workout too. Hopefully it will all come together decently in the end.

    ~Chris

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