Joining, smoothing, stabilizing, and finishing a big, wide, long, heavy desktop
Because a lot of people are moving into new home offices, we ate ProTradeCraft will be highlighting videos that will help make that process/result more awesome. Here's a handy video about making a great desktop, which is a critical ingredient in any home office.
Cut the lumber to size
The width of the 8/4 maple desktop will be 32 inches, so each board is ripped to just under 6.5 inches to keep the top consistent and symmetrical. This lumber is surfaced in three sides (S3S), so only one rip is needed to cut the stock to width.
Mark the grain pattern on the ends of the boards (smiles or frowns).
Join the individual pieces of desktop lumber
- Layout the boards so that the smiles and frowns alternate to reduce warping later in the desktop's life. Label the pieces with numbers
- Biscuits are sufficient for aligning and joining the pieces together. You can use dowels or dominoes. Put the first biscuit about four inches from the end and then every ten inches or so.
- Cut all of the biscuit slots.
- Lay the pieces in place and then rotate then such that the edges are facing up, cover the edges with glue. The roller attachment from Rockler seems to work well.
- Insert the biscuits, and then use a cheap brush to paint glue over everything.
- Lay the pieces back down and begin pushing/pulling them together.
- Snug them with the clamps.
- Add opposing clamps on the top between clamps on the bottom.
- Tighten the clamps a little at a time alternating from top to bottom, down the line.
- Scrape off excess glue after it has set up for about ten minutes.
- Let dry overnight.
Smooth the top and bottom, add warping reinforcement
- Remove clamps.
- Flatten the surface. There are many ways, in this video, he uses a Festool orbital sander starting with 60-grit and moving to 80-grit paper.
- For wide, long, or both tops, Brandon uses C-channel inset into the bottom to discourage warping. Cut slots with a router and a 1/4 inch bit. For hard maple like this, cut the slot in several passes.
- Recess the height between the slots about a quarter-inch to allow the cC-channel to sit flush with the tabletop bottom—drill holes for inserts to accept machine screws.
- Brandon uses CA glue to hold the inserts even though he is not sure he needs to. By inserting, backing out, and inserting again, he makes sure to cover all of the threads.
- Lay in the C-channel and insert the bolts.
- Now is an excellent time to square up the ends of the tabletop using a track saw or a circular saw and straight edge.
- Remove the C-channel and sand the bottom of the tabletop using an orbital sander, moving down to 220 grit paper.
- Round over the bottom edged with a round-over bit in a router.
Raise the grain
Water-based finishes can bring the wood fibers up, making a formerly smooth surface feel rough. To eliminate this problem, raise the grain with water first. Spray water on the desktop to pop the grain when dry; it will feel shaggy.
Sand again to 220 grit, and the wood will stay smooth during finishing.
Finish the top
Blow off the top with air and clean all dust from the area before breaking out the polyurethane. Brandon likes water-based poly because it won't yellow over time, keeping the maple looking great.
Apply 2-3 thin coats sanding between each. Use the same process on top, but sand with a Sciotchnrite pad between coats. And double the number of coats to at least four.