Roubo Is Coming… Part 10

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In position, and ready for the reference face to be trued up

After flattening the underside of the slab, the next surface to be processed is the edge which will face outwards when in use. This edge needs to be both straight, and perpendicular to the underside, to facilitate laying out the leg joinery, and because it will be a clamping surface when the bench is in use. With the help of my slab-manouvering assistants, the slab was moved onto my saw benches with the rear edge resting on the saw benches, and clamped to my Sjoberg workbench so that (what will be) the top of the slab was facing the workbench, and the show edge was facing upwards. The staked saw benches I built from the Anarchist’s Design Book are the unsung heroes in my workshop – they are constantly in use and are so versatile that only a fraction of their time is spent being used as saw benches. They have proved to be invaluable for this build, and have even taken the weight of the slab (which is a 4 person lift) without complaining.

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I never thought my No8 would look small, but this project does so

Planing a 110″ long, 6″ wide, edge is very different to jointing a furniture-sized board, and a clear plan is needed if you are to work efficiently and avoid chasing your tail. My plan was to get the long edges straight and flat, and then make adjustments as necessary to bring the edge to a clean 90 degrees from the flattened underside. Before I reached for any planes however, I checked the edge with a 50″ straight edge to see what I was working with. Halfway along the slab was a large knot where a branch had grown. That knot was a fair amount below the surface of the slab, and the edge of the slab had a gentle concave curve, the apex of which was located at this knot. A light swipe with a plane showed that the grain reversed around the knot, so that on each half of the slab the grain flowed from the end towards the knot.

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A sharp low angle plane is perfect for cleaning up wild grain

While this created extra work than if the slab had been closer to flat, it also suggested a straight forward solution. I worked the curve out of the edge, working from each end towards the middle of the length, using my No5 set to a rank cut. Once the curve had largely been removed, I moved to the No8 jointer to get things really straight. The grain around the knot was swirling and generally uncooperative, although moving to a low angle block plane tamed things quite easily. I am sure some folk would have flipped the slab over to avoid this knot, however I decided to stick to this orientation of the slab because the crotch wood, now it has been cleaned up, is really quite striking and will add a nice visual feature. On a practical level, turning the slab around is no trivial matter, and also requires my team of willing helpers to be available, which would slow down progress of the bench build for several  days. So in this orientation the slab will stay.

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It ain’t square until Dr Vesper says its square

Now that the edge was flat and straight I was able to check how close to perpendicular it was to the underside. A few spots required fine tuning, and for this task I quite like a No3 smoothing plane. Set to a fine cut, the smoothing plane is small enough to subtle adjustments to localised spots, which is exactly what I needed here.

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Marking the ends of the bench top

With the reference side and faces processed, I was able to remove the excess length. I deliberately ordered a slab longer than I needed so that I could trim any horrors found at the ends, and this meant that there was just over 8″ to remove to bring it down to the 8 pied a roi final length. The slab was in the perfect position to trim the ends, and so I struck a line with a 0.9mm pencil and 24″ combination square, and then cut to that line with a coarse filed cross-cut saw. The surface left by the Skelton Panel Saw is very good, so I will likely leave the trimmed ends as they currently are, without any dressing from a plane.

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The Skelton Panel Saw is basically a meat-powered chain saw, but cutting a 6″ thick, 23″ wide slab still felt a lot like work.

There is one small task left to do while the slab is in its current position, and then it will be time to flip it over and dress the rear edge. Which means that most of the work on the slab is done for now, and soon it will be time to cut the iconic leg joinery – an operation I am really looking forward to.

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The slab is now trimmed to length, and just needs the rear edge dressing

1 thought on “Roubo Is Coming… Part 10

  1. Pingback: Roubo is Coming… Part 12 | Over the Wireless

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