Lining up and cutting the bookmatch on big slabs

[William Hamilton]

I have two large 80" x 25" walnut slabs I'm preparing for a trestle table top. Anyone have any tips for lining up the bookmatch and deciding how much to take off the center? The inside edge of each slab is pretty straight so I won't have to take off much, maybe 1" or so tops. They do have a live edge. I do plan on leaving a gap in some places, á la Nakashima. I guess deciding where to cut is largely subjective? Unfortunately I'm also going to have to use a circular saw and long straight edge guide to cut them.

[Myk Rian]

A picture would help.

[William Hamilton]

here you go Myk. The bookmatch isn't perfect, though from what I've read it never is. The slab on the left was further from the pith and thus more narrow, and has some unique figuring to it. I'm thinking of taking just a little off the slab on the right... around 1" from the left edge seems to the right after looking at the grain on both. The ends will be cut later. The gap will stay.188995

[William Hamilton]

also getting rid of the remaining bark on the center with a draw knife

[Jeff Ranck]

You don't have to join them with a straight edge. You can use a curved template and a flush trim bit to follow the grain or whatever curve makes the two match well. I can probably dig up a tutorial somewhere if you decide to take that route.

[Chris Fournier]

While this may be a zig instead of a zag suggestion but I would put the other edges in the middle. I am assuming that you're keeping it close to full length as shown.

Why? Well I think that the present orientation has some challenges because as you point out symmetry is not perfect and you have the sawn waned edge combo which is awkward as it moves around "defect". I would put the other edges into the centre and then look at gently shaping the two ends of the table which would eat up the sawn portions and soften the man made/interferred look a bit.

When I do this kind work I flip and flop until my back can't take moving the flitches any more. To get the centre seam right just lay the flitches overtop of each other various amounts.

While a perfect bookmatch is tough to get it is very nearly achievable if you know which faces are the show faces in a log - then you simply machine these faces as little as possible. If the flitches were all just machined to get them flat, this is simply poor shop practice but perhaps necessary from the seller's standpoint.

[William Hamilton]

i had to flatten and surface these myself as they were pretty cupped/twisted. Thus, getting a nearly perfect bookmatch was impossible, as a lot of material needed to be removed from both sides of each to get them flat. But hey, I paid $370 for two slabs of 10/4 at 99" x 25". Flaws or not, I'm happy with that. It's my first dining table project.
I'd hesitate to put the other edges in the middle because then the bookmatch is entirely lost, and instead it would look like two consecutive boards laying side by side.
I was looking at it this morning and if I do take some from center side of the slab on the right, the figuring should line up nicely. Like you suggested, some shaping will be needed to get it just right. I will lay it on top of the edge of the other slab to get it right, like you said.
There's also going to be a .25" gap between the two slabs as well as 4 butterflies, so I think that will visually help out with any inconsistencies in the bookmatch. Wetting them prior to figuring out the cuts would probably be a good idea too.

[Chris Fournier]

The wood will always dictate how we have to handle it when it comes to pieces like this! I didn't mean to suggest that the bookmatch is anything less than acceptable either; the table will look great given the care that you are putting into design and fabrication.

[Myk Rian]

You might consider inserting a filler piece down the middle section. Matching or contrasting.
That would help to keep the width.

[William Hamilton]

going to keep the gap in there.. when I have kids in a few years maybe I'll screw a trough on the underside of the table under the gap, so food scraps, spilled drinks, etc. can be swept into it easily... maybe a squeegee holder hidden underneath the top as well (?)
Ok seriously though, I think I'm taking just a tad off the center and leaving the gap in there as is. As it stands now it's a total width of 50" so I can take it in a bit.