Undercarriage Assembly

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Gluing and wedging the legs into the seat is pretty easy if you don’t have stretchers between the legs. But there are still lots of opportunities to mess things up and get into a bind when you open the glue bottle.

Here’s how I prepare for the glue up so I don’t have many surprises.

First I knock the legs into the seat and pencil around all the tenons – both above the seat and below the seat. The mark around the tenon above the seat tells me about where I should crosscut the tenon before assembly. The mark around the tenon below the seat tells me at what point I should stop sawing a kerf for the wedges.

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With the legs still in the seat, I also number each one and mark its position in the seat so the leg’s annular rings run parallel to the grain in the seat. I know that this runs contrary to some sound advice out there. Here’s my rationale:

If the legs are going to shrink, they are going to shrink more in the direction parallel to the rings than they will shrink perpendicular to the rings (that’s the way trees work). So I want to apply a wedge against the annular rings to resist this shrinkage. So the annular rings in my legs run front to back, the grain in the seat runs front to back and the wedge cuts across the legs’ annular rings.

Honest: I am not trying to talk anyone into doing it this way, and I am certain other tactics work. But this is what suits my head at this time.

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Then I kerf the tenons with a tenon saw, stopping short of the pencil line representing the underside of the seat.

I gather all the materials I need for assembly and lay them out on the bench. This includes extra wedges, rags, a toothbrush for cleaning up the glue, a cup of hot water, several mallets and hammers and a 1/2″ chisel.

To assemble, I paint hide glue on the inside of one mortise. Then I paint glue on its tenon and drive the leg home. I strike the leg with a 2-1/2 lb. sledge until its stops moving into the seat when I strike it. Repeat for the other three legs.

I clean up any glue on the underside of the seat then flip it over.

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Usually, driving the legs into the seat will close up the kerfs I just sawed in the tenons. Instead of trying to wedge the closed kerf and risk destroying some wedges, I open up each kerf with a 1/2″ chisel and a few mallet blows. This reduces wedge failure by about 345 percent.

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I paint glue on a wedge and drive it in with my hand sledge. When the wedge stops moving, I stop hitting it.

Finally I clean up all the glue I can find with rags and a toothbrush. I put the chair on a bench and walk away, resisting the urge to fiddle with it too much and make it worse.

— Christopher Schwarz

About Lost Art Press

Publisher of woodworking books and videos specializing in hand tool techniques.
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14 Responses to Undercarriage Assembly

  1. jpassacantando says:

    Again, thank you. These little notes are super helpful for those of us working our way through the Anarchist Design Book.

  2. Christopher
    Do you think 3D PRINTING will change woodworking as we know it nowadays?
    Thanks

    • On the industrial side, absolutely.

      For those who do it as a hobby and are process-driven, likely not in the immediate future.

      Many of us go to the shop to disconnect from the screen, phone and computer code.

      Don’t get me wrong, I love technology. But I’m not personally interested in bringing high tech into the area where I enjoy to explore low tech.

      Not a good answer, I know.

      • jayedcoins says:

        100%!

        What drew me to woodworking — specifically hand tools — was that it could act as an escape from my profession of software development.

        I still quite like my job and will always enjoy having a hand in the software world. But I have come to at least equally love minimizing the amount of computer tinkering I do outside of my job, in exchange for a few hand planes, chisels, and saws.

  3. wilburpan says:

    I have to file this trick away for later use. If the chisel trick reduces the wedge failure rate by 345%, then this process will generate new wedges as you make the chair-leg assembly. That’s a real time-saver!

  4. Thanks Christopher for sharing you’re knowledge! Greetz from Holland

  5. tsstahl says:

    I’ve said for years that I suck at chairs because my 3 forays into arse parking came out so dismally.

    However, I might could do this. I even have the lee valley tenon thing kicking about somewhere from a rustic bench build some years ago. After all, that rustic bench was simply inelegant staked furniture!

  6. jmac406 says:

    This request doesn’t apply specifically to this post but it does to the chairs in the Anarchist Design Book. Living in Montana the wood that I have available to me that might be green or air dried are:
    Pine, Larch, Spruce, Douglas Fir, Cedar, Aspen, Cottonwood, maybe some Willow or Hemlock. Which of these would be a first to try for the especially for the spindles and crest? I’m willing to experiment but it would be nice to start with an educated opinion. Thanks for any help or direction.

  7. Reblogged this on Journal Edge and commented:
    Article Source: blog.lostartpress.com

  8. haurykjo says:

    When using a tapered reamer (such as the basic one from Lee Valley) in a drill press, is there a recommended maximum speed? I’ve been having trouble with mine burning the wood (smoking actually) once it’s fully buried in the pilot hole. My el cheapo Delta drill press only goes down to 620RPM. So I tried it in a powered hand drill, but had the same result. Actually even more smoke. Maybe I have ruined the reamer? I’m actually making Roorkee legs, not Windsor legs.

    -John

    • Lee Valley recommends about 500 rpm so 650 is fine.

      My guess is you might be using too much downward force. Light cuts are essential. If you use too much force, the body of the reamer burnishes the inside of the hole, the edge stops cutting and smoke billows out. If you heat up the edge too much, then you can soften the edge of the tool, worsening the situation.

      My recommendation would be to sharpen the inside edge of the reamer’s cutter. Then use the reamer in a brace to slowly scrape away any burnishing. Then return to the drill press (or finish with the brace).

      One other detail I’ve encountered with students making Roorkhees: It’s best to have the leg clamped down *very securely* when reaming. When the leg wobbles, students would tr to stop the wobbling by overfeeding the reamer, resulting in burnishing.

      Good luck!

  9. haurykjo says:

    I definitely recall pushing down hard with the drill press in order to stop any wobbling, in addition to trying to hold the piece with my off-hand. This may have been the issue. Thanks for the advice.

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