This table is built from an antique game table top and repurposed legs with casters. When using reclaimed and antique materials, always keep the remnants and drops to repurpose in other projects. Finally, check materials for cracks and any other structural damage.
To attach the new base to the top, you will also need a piece of 3/4" plywood and some reclaimed 1x8 material to form the skirt.
With the antique top upside down, determine the best place to mount the new base skirt. Look for underlying structure with enough material to drive wood screws through. The top shown was framed with an underlying square (where the legs folded down) that was an ideal place to attach the base. Cut a piece of 3/4" plywood 1-1/2" smaller than the base skirt but still large enough to fit into the underlying structure. Attach plywood with 1-1/2" wood screws at least 12" on center. Next cut two pieces of reclaimed 1x8 to the same length as two opposing sides of the plywood. Coat the edge with wood glue and attach to the side of the plywood with 15-gauge finish nails.
Cut the remaining two pieces of 1x8 to the outer dimension of the two sides just attached. Check the upper and lower width of the side pieces with a measuring tape and framing square to make sure that they are parallel. Slightly push or pull each side so it is square with pieces three and four prior to attachment. Coat three edges of these pieces and shoot on with finish nails.
To attach the four table legs, cut four 6" triangular gussets from the remaining 3/4" plywood. Leg style will determine mounting method. For table shown, the top was wood glued to the top of the leg; a 3" #10 wood screw was driven down through the gusset into the leg. Mounting method must be secure enough to prevent the legs from racking while rolling. Some legs may already have a threaded rod in the top, which would be an excellent way to attach to the gusset. If the diameter is large enough, drive two screws into the tops of the legs.
Depending on mounting method, it may be easier to attach the gusset first. To attach the gusset, coat the two 6" edges with wood glue and install two 1 1/2" #8 wood screws through the 1x8 on each side.
Several options are available for finishing this coffee table, such as painting, staining and waxing. For table shown, the 1x8s were planed. Much of the original texture and patina still existed under the surface of the wood. A furniture-grade wax was used to protect and bring out the color of the table base. The legs and top needed no additional finishing. If you choose to sand and repaint or refinish, be careful to check for any possible lead-based paint first. Consult the EPA's Renovate Right: Important Lead Hazard Information for Families, Child Care Providers, and Schools pamphlet for further guidance.