Friday, February 11, 2011

Ming Inspiration (31)

You've arrived at yet another post on this dining table project, a piece based on some structural ideas gleaned from a one-of-a-kind Ming Chinese table. Previous postings are archived to the right of the page, and stretch back into November 2010.

Today I return to the cutting work on the banwancheng, or giant's arm braces. These braces run at an 45˚ plan angle from the central rail to each corner leg, and are curved as well. The cutting work on these four pieces is in fact some of the most difficult on the project due to the nature of the pieces being curved and due to the form the joints take.

In post 29 I showed the roughing out and template routing of the four pieces. I then had used a jig to fix the work in position for subsequent steps. One of the first of those steps involved roughing out the lower end joint on the braces - here is where I left off earlier:


I then used the same jig with the sliding table saw in the upstairs shop to cut the 45˚ abutments. I learned an interesting point about that saw, in regards to it's splitter. When I had the blade tilted over and had completed my cut, unbeknownst to me the splitter was a bit high and my jig got hung up on it as it exited the cut. Withdrawing the jig led to a sudden binding and in a flash one of the cuts was spoiled. Not happy news. I went down to my pile of bubinga to scratch out a replacement. I found one chunk of material which was quite flat grained and with some checks on one face, but otherwise usable. I had no other pieces except for a massive slab I pretty much would rather saw my arm off than cut into. So, I then had to slice a blank out of that chunk, due to its extremely flat grain pattern, by correcting and resawing at an angle, a process that took me half an hour. An hour later though I was up and running again and, with the saw's splitter lowered out of the way, could continue with the saw work. Whew!

Saw work done, I used the same jig to effect the cutting of the upper face of the lower joint, and forgot to take pictures - sorry!

With the shoulders of the lower joint roughed out all around, I could then dimension the 'tenons', which involved taking a 1/4" (6mm) slice off of both faces. Again, my resaw band saw proved rather helpful:


The four pieces now with the lower joints largely roughed out:


Time to clean up the inside acute angles on the beaked portion of the joint alongside the tenon cheeks:


I quickly realized that the flush cutting saw was not the tool of choice here, and went over and grabbed my azebiki and flipped the rip teeth into engagement:


Then a little chisel work:


Some additional paring and a few saw drags and the work was done.

The joints tart to look a bit more cleaned up:


Here's all four:


More to do on those lower ends yet, but I switched gears slightly and started in on the upper end connection on these braces. Again, using the same fixing jig, I made the initial 45˚ slices on the upper ends:


End miters trimmed (leaving a little extra there for paring later on), I then set up to remove a chunk of material from the end so as to leave a tongue. I took the existing fixing jig and built a second jig to hold it at 45˚:


Again, the Hitachi proves itself a superbly accurate machine:


The re-saw produces a kerf which defines the under-surface of the tongue. Next step is to saw across the brace at 45˚, so I went upstairs and set things up on the sliding saw:


You can see the pair of mdf strips in the foreground, with a framing square around them- I always do some test cuts to prove the cut is exactly 45˚ before running the material through. The fixing jig in the background has a brace fitted into it, poking out the bottom.

Then I did some judicious positioning of the fixture jig to locate the cut just right:


And zing! the cut is made:


I love sliding table saws! Although many associate them only with slicing up sheet goods, they are without doubt in my mind the best choice for joinery work. One day I hope to make friends with a Martin T-73..

The result:


A while later, all four pieces were through to the same stage:


And a good while after that, with a bunch of jig set up and fiddling, I had completed the joinery work (not illustrated) on the upper end of the braces:


Completed, that is, save for some chisel clean up at the places where the dovetail meets the underside of the tongue. The dovetails are cut with a Japanese 8mm bit with the dovetail angled at 35˚, and I have tapered the dovetails from insertion to end point 0.5˚ each side, for a total taper of 1˚ along the length. That way the dovetails self-tighten as they are driven inwards. Of course, I'll have to make the dovetail mortises in the central rail (yet to be done) match that taper.

Next up on these braces will be the completion of the joinery work on the lower ends. Then i will be doing some work on the profiles of the braces generally. I should be able to make some progress on that tomorrow, and will be posting up at the end of the day.

Thanks so much for all the comments on the previous post, and I'll be tackling the responses in a couple of minutes.

See you next time on the Carpentry Way. --> on to post 32

2 comments:

  1. I have been loving this project! When I get into a project, I can work on it into the night only to find I worked until 3:00AM and have to get up at 7:00AM. When fitting a joint the sword tip miter, it seems the tiniest shaving takes the longest time to make. . . WOW! that should be a bumper sticker.

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  2. Hi Paul,

    it's not so much that a shaving takes all that long to make, it's more the case that I take a shaving or two, try the fit again, square things up, reassess, mark where I want to remove material, take it apart, pare another pass or two, then resharpen from time to time, and repeat. it eats time. Glad you are enjoying the project - me too!

    ~Chris

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