Post 33 in an ongoing series.
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Today’s task was to deal with the double hammerhead keys which lock the ends of the breadboard ends to the table slab:
There are two main aspects to the task: mortising the slab and breadboard ends, and making the ebony keys. My goal for today was to complete the mortising.
While these hammerhead joints are somewhat novel perhaps, they are ‘just’ another joint, a series of cut out tasks to be completed. However, what made the work anything but usual was the realization that the parts were not exactly easy to replace should something go wrong. I mean that particularly in reference to the table slab, which started out as a 3″ thick chunk of vertical grain bubinga. I don’t know of any other 3″ thick slabs of bubinga on the market at the moment, or any coming along anytime soon, let along a perfect vertical grain piece. And in any case, if such a piece could be found it would likely be far more material than I actually needed and I’d be looking at several thousand dollars. They don’t just sell 24″ squares of 3″ thick bubinga. So, it was most definitely the case that I did not want anything to go awry in the joint cutting on the table slab. Uh-uh, nope. No way.
Adding to the ‘irreplaceable’ aspect to the slab was the fact that I already had many hours into the fabrication of the top and breadboard ends. Every visit for marking out and cutting is an opportunity to screw something up. And added to that, I would be cutting the joints in a hard wood with a somewhat slender and long router bit at max. extension- I was apprehensive about the chance it might flex slightly, catch and possibly break, possibly ruining something wooden.
So, while not feeling abject terror perhaps, I was a little stressed out and took on the task today with great deliberation and care. Hyper-focus even. Some of the cutting was a mix of routing and chiseling work, back and forth, until the joints were cut. In the end, everything came out well. Whew! The bit did its job without breaking, and the joints are to dimension. I found camellia oil helpful as a cutting lubricant.
Here’s one corner, with the breadboard end re-attached:
Another view of the same corner:
A different corner:
The crosswise mortises are for some 1/4″ (6.35mm) pins which will be wedged at each end to tie the works together.
Another view – not the best picture:
Corner 3:
Corner 4:
I also mortised the central part of the breadboard ends for their connections to the middle tenons on the table slab:
All for today. Tomorrow will be key, if you know what I mean. I’ll try not to get too keyed up about it I guess. :^)
If it is of interest: post 34
CHRIS;
The key to life is the details and turning the key to unlock all that is possible! Double hammerhead looks like it will work out nicely1
J.T.
Hey Chris,
Where did you pick up the router bits with the “hammerhead” profile and what is that profile called for ordering? I've been searching for them here in Japan for some doors I'm working on, but can't find them anywhere. I've seen them used here a while back on a type of router table with the motor above the table… not the safest looking setup. When I went back to the shop to ask about the bits they were using, I found the shop had gone out of business.
By the way, that grain in the table top slab is just sick looking… in a good way. It has such a mossy blotched look that I've never seen in bubinga before.
Thank you,
Kiku
Chris
So i'm trying to figure out that if this hammerhead slot you made isn't on an angle and it's two 90deg cuts how is the key inserted? Is the key 2 parts, the anticipation is killing me, can't wait until tomorrow.
John G.
Kiku,
thanks for the message. I drew the profiles up on the computer and had the bits – 4 different ones – custom made by Ridge Carbide Tool.
I've seen them used in Japan as well – perhaps try contacting a larger maker of shōji, as that is where they see more use. I've seen them set up in a hollow chisel mortiser, using an adapter with a drill chuck mounted. I think a router is better perhaps – debatable.
~C
John G,
I will say for now that the keys are one piece construction. I didn't quite get them finished today – 3 out of 4 corners – so it will be tomorrow until I show them fitted up. As far as how the joint works, I'll save showing that until the final assembly portion of the build, so I'm afraid you'll need to be patient a little while yet. A few other surprises coming as well…
~C