Even with the most careful glue-up job, there will be at least a little board-to-board misalignment when your tabletop comes out of the clamps. This is where cross-grain sanding helps. With an 80-grit abrasive in your belt sander, level your tabletop by working across the wet carpet Brisbane grain instead of parallel to it. This removes wood more quickly, making it easier to create flat results. Move to parallel-grain sanding with the 80-grit belt when all joints are flat, then switch to 120- and 180-grit belts, also run parallel to the grain.
Although it’s tempting to use a random orbit sander to smooth your table top at the final stages, I never do. Finish quality is the reason why. Random orbit sanders often leave behind swirl marks that don’t show up until finishing time. A better option is to complete the sanding process by hand, using 180-, then 220-grit paper only in the direction of wood grain. The finish of a tabletop is more closely examined than wood finishes anywhere else, so you need to eliminate all flaws.
Leave your tabletop longer than necessary until the sanding is done, then cut to final length. Most tabletops are too wide to trim on a tablesaw, even with a crosscut sled, and this is where I use a hand-held circular saw. Clamp a guide strip so it’s square to one edge, then follow it with your saw. Repeat the process on the other end, then carefully use your hand-held belt sander to remove any blade marks on edges.
Tabletop edges take a lot of wear, and rounding them helps the finish on edges to last longer. Even if you prefer the look of a square-edged tabletop (as I do), rounding over with a modest, 1/8” radius router bit does a lot to extend finish life.
When it comes to choosing a finish there are two main choices. The typical approach of stain and urethane creates a smooth, wipeable surface, but when that finish eventually wears through, there’s no way of repairing it attractively. Sanding back to bare wood and refinishing is the only way to make it respectable again. Oil and wax finishes, on the other hand, take more time to apply initially, but they’re easily repaired and rejuvenated with the tabletop in place. Regular reapplication works just fine.
Like all woodworking success, building a tabletop depends on properly completing each step before moving on. The only difference is that tabletops are probably the most obvious and prominent woodworking you’ll ever do. All the more reason to get things right.