Lay the wooden, wire spool on a 4-by-4-foot sheet of 1/4-inch to 1/2-inch thick plywood. Draw all of the way around the edge of the spool with a carpenter's pencil and set the spool aside.
Set the plywood sheet across a pair of sawhorses. Using clamping blocks between the cups of each C-clamp and the plywood to prevent damage, secure the plywood in four places.
Cut around the outside of the circle you drew on the plywood using a jigsaw.
Make relief cuts as needed, from the edge of the plywood to the edge of the circle you drew, to prevent twisting or binding the saw blade as you cut along the circle. Save the plywood scraps to use as clamping pads or shims for other projects.
Examine the wooden wire spool for any protrusions on the side you intend to use as the tabletop. Sand these protrusions -- which are usually around the spool hole -- with a coarse belt on a sander until they are even with the rest of the spool surface.
Place the plywood circle on top of the sanded side of the wooden wire spool. Use clamping blocks to pad the cups and apply C-clamps in at least three places around the tabletop to secure the plywood to the spool.
Determine what screw length you need. Measure the total thickness of the tabletop from the top surface of the plywood to the underside of the wooden spool. Subtract 1/2 inch. Use 2 1/2-inch long wood screws, for example, if the thickness of the plywood plus the spool is 3 inches.
Mark screw positions on the tabletop, 2 inches from the outside edge, every 6 inches around the perimeter of the table.
Drill a pilot hole for each screw, using a 1/8-inch diameter bit. Switch to a countersink bit.
Countersink each screw hole to accommodate the heads of the wood screws. Position the countersink bit so that you are drilling at a 90-degree angle.
Drill down a little at a time, stop and place the screw in the hole. Remove the screw and drill again if needed to allow the head of the screw to sit below the surface of the wood and leave room for wood filler.
Remove the clamps and clamping blocks and set the plywood sheet aside. Apply carpenter's glue to the entire upper table surface and one side of the plywood circle, using a 3-inch-wide paintbrush. Allow the glue to cure for about 10 to 15 minutes.
Position the plywood circle on top of the glued surface of the spool, glued-side-down with the screw holes aligned. Reapply the clamps and clamping blocks.
Insert all the screws. Tighten them just enough to secure the plywood to the spool without squeezing much glue from between the two surfaces. Wipe away any excess glue around the edge of the tabletop using a clean, soft cloth.
Fill the screw holes with wood putty. Rub a polyester kitchen scrub pad over each hole to smooth the holes and remove any excess putty on the surface of the table. Allow the glue and putty to cure overnight.
Smooth the surface of the table and along the edge using a medium sanding belt on the sander. Wipe away the dust from the medium belt using citrus-based, all-purpose furniture cleaner on a clean, soft cloth.
Switch to the fine belt. Smooth away all sanding marks from the previous belt and wipe away the dust with another clean, soft cloth.
Apply at least three coats of clear acrylic sealant to the entire table, including the underside of the tabletop, the center core of the spool and the upper side of the base. Allow each coat to dry overnight in between coats.