Keeping That Top FLAT

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Router Techniques Woodworking

If one or both plywood panels for your tabletop are bowed, don't worry. Orient them with the crowns in. As you apply the clamps along one edge during glue-up, the others will tend to open up. Eventually, the clamps will close the gaps, and the bowing will spread the pressure across the entire surface. The glue bond will be that much better overall, and the bowing of one sheet will counteract that of the other, leaving you with a flat tabletop core.

If one or both plywood panels for your tabletop are bowed, don't worry. Orient them with the crowns in. As you apply the clamps along one edge during glue-up, the others will tend to open up. Eventually, the clamps will close the gaps, and the bowing will spread the pressure across the entire surface. The glue bond will be that much better overall, and the bowing of one sheet will counteract that of the other, leaving you with a flat tabletop core.

How many times have you experienced this at the lumberyard?

You pull the top sheet from the stack of plywood. The exposed face has picked up moisture from the open air, while the other face, having been virtually scaled against the sheet beneath it. has stayed drier. Is this sheet flat? Though we think of sheet goods as being jlat, we all know from experience that they aren't. One face gets damp, the other stays dry: The sheet cups.

If you apply laminate to one side of plywood or particleboard or even medium-density fiberboard (MDF), you are setting it up for a warp. The laminated side will stay dry. but the unlaminated side can pick up moisture. The panel is out of balance. The damper side will expand, and the panel will cup. In context, your router will be in a subtle saucer.

You want a FLAT tabletop. So...

• Laminate both faces to create a balanced panel that will stay flat.

• Seal the edges as well. If you apply hardwood edge banding, seal it with a couple of coats of finish.

• Paint or otherwise seal the edges of the mounting plate opening.

• Forget the miter gauge slot in the tabletop. It's unnecessary (sec the chapter "Router Table Acces-501165"), and it breaches the seal.

Slide one against the other, moving them slightly back and forth. Align the edges. Apply clamps around the edges, letting the core cure overnight with the clamps in place.

3. Prepare your edge-banding stock. As previously noted, it should be made of a hard, straight-grained hardwood like maple, ash, oak, or birch. It should be wide enough to stand slightly proud of the plywood core on both sides, and about V* inch thick. Make it about 1'/«inches wide for a 1-inch-thick core. 1% inches for a 1 '/2-inch core. After it's applied, you'll use a router and flush-trimming bit to—what else?—trim it flush with the plywood on both sides.

4. Unclamp the core, and square it up on the table saw. Cut the edge banding to fit. mitering it at the comers. Glue it in place. After the glue dries, trim the banding flush.

5. Now you are ready for the plastic laminate. Cut the two pieces required to make a balanced, stable, warp-resistant top about a half to a full inch larger than the edge-banded core. Because of the irreversible nature of the bonding process, and because you will trim the edges of the laminate after installation anyway, it's best to cut the pieces with extra length and width.

You can saw laminate with car-bidc-tippcd blades, cut it with carbide router bits, or score and break it. For the last type of process, use a special scoring tool, which you can buy for $3 to $5. Laminate will chip out quite easily as it's sawed, and the chips are hard and sharp. Wear those safety goggles!

6. Contact cement is what bonds the laminate to the substrate. It's a sophisticated rubber cement that you spread on the mating pieces and leave to dry-. When you touch the dried cement on the laminate to the dried cement on the substrate, they stick. Immediately. Therefore, the laminate must be accuratcly aligned before it can be allowed to touch the substrate. A typical approach is to lay dowel rods or sticker strips across the substrate, and then set the laminate on them. Beginning either in the middle or at one end, you pull the spacers out one at a time and press the laminate to the substrate.

Repeat the proccss to apply the laminate to the other side.

7. Complete the top by trimming the laminate, slightly beveling the edge of the laminate and the hardwood

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Wood Working for Amateur Craftsman

Wood Working for Amateur Craftsman

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