Photo 9- When you glue and clamp the slabs, you must ensure that they stay reasonably flat. The layers can "wind" like an oriental fan, producing an interesting sculpture that is useless as a bench top.

Glue up each of the plates as in photo 9. There is a serious danger present when gluing up a long lamination like this, that being that it will not be flat. The clamping pressure can tend to twist it, like an Oriental fan opening. To guarantee against this, place winding sticks on either end of the glue up to check the alignment. These are simply straight boards that show you if both ends of the lamination are parallel or not. Place the sticks perpendicular to the laminations. Align your sight along the tops of the two winding sticks, and you will quickly see if the two tops are not parallel. If not, the lamination is "unwinding" and you need to loosen the clamps, tweak the layers, and clamp up again. You won't be able to get it perfect, but you need to get it fairly close. The router planing jig will flatten minor twisting, but it won't make a silk purse out of a sow's ear.

Photo 10- Flatten each slab with this router planing setup. The two long guide rails upon which the router jig rides must be parallel to each other. The slab surface must be a uniform distance from the long guide rails at all points, or close to it.

Flatten the plates with a router planing setup as in photo 10 after the glue is dry. Use a 1" wide straight flute carbide bit to plane the surface. How flat the resulting surface comes out will be a function of how carefully you set up the guides that the router travels along during the cut. Check and double check your setup before you cut.

The setup consists of two major components. The first is the base to which the router is attached. This is simply two guide bars with a piece of plywood between to which the router base is screwed. These two bars must be parallel to each other, and straight.

The second component is the combination of long guide bars and clamps that you attach to the laminated plate. There are two things to watch for here. First, the two bars must be parallel, and you can check that with winding sticks placed perpendicular across the bars as described above. Secondly, you must locate the top of the plate itself at a uniform distance from the top edges of the two guide bars. It can't be closer to the guide bars on one end than it is on the other. Since the plate isn't flat you can't get it at a perfectly uniform distance everywhere and still keep the bars parallel, but you must get the distances as close as possible to each other given the amount of out-of-flat you are dealing with.

Set the router depth to cut below the area of the plate that is farthest from the long guide bars. Put on your ear plugs and dust mask and plow forth. Then flip the plate, and again align the long guide bars. But this time align the plate so that there is a uniform distance from the bottom side of the plate to the top of the guide bars. This ensures that the planing done on the second side will be parallel to that done on the first. As well, by adjusting the depth of the router on the cut on the second side, you can adjust the final thickness of the plate.

No, it's not 100% precise. My slabs came out fairly flat and straight but not perfect. If you want a perfectly flat top, get out your handplanes after the top is all assembled and get crackin'. Use winding sticks to show you where to reduce the surface. Or, find a 16" face jointer and large planer, but be prepared for the owner’s grimace when you tell them you want to push glue lams through their knives. Glue dullens steel knives fast.

Align the top surfaces of the plates with dowels, located with a dowel jig. Use four or five dowels along each joint, and glue the dowels into only one of the two holes, so the plates can be disassembled.

Use a 1" Forstner bit to enlarge the holes for the threaded rod at the front and rear of the whole slab. Start these holes using a guide block that has a hole cut in it with the same bit. These larger holes allow the nuts and washers on the rod to be recessed within the top.

Photo 11- Attach the rear of the top to the rails with cleats that have small tongues fitted in grooves in the rails. This will allow the top to move with moisture variations.

Secure the top to the top rails with two lag bolts at the front of the rails, and a sliding keeper cleat at the rear. The sliding keeper allows the top to expand and contract with moisture variations through the year. Which raises an interesting question- what will happen to the threaded rod as the wood expands? The wood by the washers will crush, and the rod itself may stretch. Check the nuts from time to time and tighten them as necessary.

Resources for building a Traditional Workbench