Friday, January 23, 2015

Gateway (39)

Post 39 in an ongoing series describing the design and construction of a kabukimon, a type of Japanese gate. This is a project for the Museum of Fine Arts in Boston. Post 1 in this series can be found here if you'd like to start at the beginning. Each post links to the next at the bottom of the page. Recent installments also to be found in the 'Blog archive' index to the right of the page.


Continuing on from yesterday's work, I fitted the double hammerhead keys to the magusa:

Just a look-see to check that they would all enter their respective mortises at the same time:


I then turned my attention to completing the joinery between the nose pieces and the kabuki. Here I'm employing lapped rod tenons running right through the post, secured top and bottom with a pair of tapered parallelogram-shaped keys called shachi-sen. 4 pairs of keys, male and female halves -- four hours of shop time. Here's a video showing a few highlights:

The trenches for the pins lined up okay and I was pleased with the outcome:

The view is with the magusa also in position - I left just enough room at the front face of that stick to slide the key in.

The other side:

A little adjustment to come yet, but seems to be most of the way there.

All for today. Thanks for your visit and hope to see you again. Onward and upward: post 40


  1. Great video, Chris. It's nice to watch the joinery in action.

    1. Tico,

      pleased you liked the video. Thanks for the comment!


  2. It appears that the hammerhead key mortices would be more effective were you to flip the magusa 180º, the the keys would be captured as you drive them home.

    1. Jonny,

      thanks for the comment. I understand your observation however there are a couple of issues with that idea. For one, offsetting the sliding mortises in that direction would mean that at one end of one of the sticks the mortised portion would be quite close to the end of the stick and I'd rather avoid that. For another, there is the matter of separating the parts after checking the fits of the two beams together with the keys in place: while the keys would be captured in one direction, they would slide back an unpredictable amount in the other, which could make the two beams impossible to separate: a disaster. Joinery should, ideally, be reversible, whether for trial assembly or for repair down the line.

      The solution to the 'key sliding problem' is to fit plugs into the mortises on the stick which receives the keys first (place the keys in, drive them tight, then fit plugs into those mortises) thus trapping the keys in position on that stick. Then the assembly can be fitted to the other beam, driven along to lock, and then driven apart. With the use of these plugs, it doesn't matter in which direction the hammerhead keys are inserted in the first stick.

      A final aspect to this is that the plugs serve to block the entry of water into the open mortises, which could happen as the timbers are exposed to the weather - moisture could wick into any gaps which might open between the parts. In this case, the magusa is the piece on the bottom and is more vulnerable to this issue with its key mortises upright and against the kabuki, so it is the magusa which receives the keys first and has its mortises plugged. Make sense?


  3. Replies
    1. Siavosh,

      glad to hear it - will endeavor to continue in that vein.


  4. I was wondering that myself - great explanation.

    1. Owen,

      I presume you mean in reference to the question posed above by JonnyC?

      If so, I'm relieved that my explanation made good sense to you.



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