Friday, February 25, 2011

Ming Inspiration (44)

Post 44 in this thread. All of February's posts would appear to be devoted to this topic. It's been a good run - you'll find previous installments in this thread archived to the right of the page, and if you wish to read about something else, a mosey on over to the labels index might serve you well. Thanks for dropping by.

Yesterday's post ended with the table frame sitting, I mean standing, and ready for the next steps in the process:


The first task on the slate today was to level across all the battens and their associated landings at the points where they connect to the outer and central rails (landings which will become male dovetail stubs soon enough). I devised a jig which rode across the three principal frame members:


Some fiddling and router calibration was required, and then I went to work leveling the surfaces - I removed anywhere from '0' to about 0.015" of material or so from the exposed surfaces:


Another view, after a pass with the router:


I was guiding the router freehand, so I kept my distance from the central protruding rib - the remaining bit of wood left on the raised platforms on either side of that rib I simply trimmed down with a chisel:


It all went pretty well I thought.

Then I thought it was time to change things around a bit - why was I stressing out over those precious bubinga edge grain top panels, when a couple of pieces of Baltic birch ply would surely serve the same task so much more admirably? Why, with the plywood, any concerns about wood movement would just dissolve into irrelevancy and I could make the ply fit the top frame with little to no gaps. That sounded like a good idea! I could even stain the ply to match the bubinga.

So I tossed the bubinga top panels in the trash- they were starting to bug me anyhow - and commenced fitting the pure, lovely white Baltic birch panels:


What do you think of the change? A bit radical I guess, but it's really time I starting getting hip to these modern materials and stopped being such a curmudgeon. Solid wood is so yesterday - that's what they tell me.

Of course, I'm pulling your leg. I hope I had someone going though, even just a little bit!

There was in fact a bit of cutting action today involving the bubinga top panels. I did a little scraping on the back side of the problematic one, which was still quite cupped, and I decided to put it to one side and work the spare piece of material (the leftover slab from earlier in this thread when I had the top panels re-sawn) into a substitute role. That spare slab had once been 1.25" thick or so (or was it 1.5"?), but after a session of many light passes through the planer upstairs, then many, many passes through a thicknesser, I had a new 0.5200" thick replacement. No pictures of that though, however it is, to my considerable relief, nice and flat. Yes! Looks like the crisis of the warped table top panel has been sidestepped, at some loss of material of course. I probably planed away $300 in wood on that one slab....

So, what was up with that last picture and the Baltic birch ply? Well, I am using it to make a large two-piece jig for routing the dovetail slots on the backside of the table top panels. I realized a while back in one of those late night toss and turn sessions that one of the challenges in this project, given my joinery choices, would be getting the dovetail mortises on the underside of the top panels in perfect congruence with the battens. One can imagine that if a batten on one end was slightly misaligned or not exactly on spacing, it would present assembly problems, as the battens must get pre-fitted to the table top as a group. Then that assembly must engage with both the central and outer rails - counting the twin stub tenons and yatoi-sen slot mortise on the outer ends, and the housed box tenons with rod tenons on the central rail, there were 25 points of simultaneous engagement. Yep, it was pretty critical that the alignment of the dovetail battens, in situ, was perfectly reflected on the underside of the table top.

My solution was to create a giant template which referenced directly off of the batten locations, a template that could then serve double duty as a means of producing the dovetail mortises. That was the theory at least. Let's see what unfolded.

With the plywood template secured to the table top in the required position, I flipped the entire top, sans legs, over:


Then I pulled some 2.5" ply strips tight against the sides of each batten and screwed them into place to the master template halves:


I then flipped the entire works over again and ground the protruding screw tips down, a step which later proved to be completely unnecessary:


With both sides done, I extricated the templates from the table frame assembly, and commenced adding small pieces to extend the templated lengths of the battens:


I then had to scab on a strip to one side of the template and place small extension pieces on that side too. Once all that work was complete, I used my jigsaw to rough out the openings between guide strips:


A trim router was then used to trim the openings flush to the guide strips, as seen above.

Here's one side template/jig complete:


Another hour or so later and the other side was also done:


By that point it was getting late in the day and I was pretty tired, so I decided to table the next steps, until later. Sorry - I couldn't help that rather bad play on words!

More to follow tomorrow as I apply these jigs to the table top panels. That should be entertaining to say the least, and a little stressful too.

Hope to see you then! --> on to post 45

2 comments:

  1. Chris

    The table is looking more splendid with every post. Fascinating as always.

    Tom

    ReplyDelete
  2. Tom,

    thanks for the comment and support - I'm getting excited to see this piece come together in the next week!

    ~Chris

    ReplyDelete

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