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Begin the job at a quarry or stone yard and pick out the stone for the table top. Look for something proportional in size to a coffee table: about 3 feet long, 2 feet wide and 2 inches thick (Image 1). When choosing a stone, pick for color and character, but also make sure the stone doesn't have cracks or imperfections that will compromise the strength of the table. Transport the stone back to the work site carefully and lay it flat on a pallet or bed of sand. This will provide adequate support for the stone piece while you work on it.
The base of the coffee table can be made of almost anything as long as it's capable of holding the heavy stone top. Options include an old coffee table base, a tree stump and interesting junk yard finds. If you choose the latter, head to a junk yard to find material for creating a welded steel base. Look for structural steel for welding. You don't want aluminum, stainless steel or cast-iron. A piece of cylindrical schedule-40 pipe (Image 2), a plow disc base and leaf springs from an old truck are an example of a good option.
To get the stone to the desired shape, use a stone hammer and carbide chisel (Image 1). If you want a more geometric shape, you may opt to use a circular saw or grinder to score the initial shape (Image 2). When shaping, you can either freestyle with the hammer and chisel or mark out the design ahead of time with a chip of stone or chalk.
The smaller the section you try to take off at one time, the better. The larger the section you attempt to remove, the more likely the stone is to break in an unexpected place.
Further control the chiseling process by undercutting: cut out the bottom half of the edge with the stone hammer and chisel before chiseling off the top line. Undercutting reduces the amount of stone you're cutting, thus making the cuts more precise.
Once you've chiseled the shape of the stone, follow up with a lighter hammer and a finish carbide chisel to remove sharp edges. Always wear safety glasses when chiseling.
The stone top can be finished whenever you achieve your desired look, but you can choose to add artistic elements to the stone top. Sketch the design out first with chalk, and follow the chalked lines with a saw or grinder, scoring them about an eighth of an inch deep. A circular saw with a diamond blade is best for straight lines and a grinder best for curved lines. If you want the scored lines wider, go over them a second time.
The next step is to add a colored stone inlay to the pattern. The inlay consists of crushed stone, epoxy, and hardener and can be obtained from specialty craft stores (Image 1). Mix the inlay and spread using a syringe (Image 2). Run the syringe slowly in the grooves and try not to overfill. If you add a color, make sure the powder is finely ground as it must travel through the narrow passage of the syringe. Let the inlay harden before doing any additional work on the stone, which takes about four hours depending on the product used.
The stone top can be left uncovered, but certain stones stain easily and all absorb water. You can either seal the stone to get a natural finish or apply a clear resin to give the surface high gloss.
Elevate the stone on top of plywood or scrap wood. Pour the clear resin over the stone, spread and smooth with a tongue depressor, and let it drip over the edges. The resin can be spread on the edges with a tongue depressor or paintbrush. Let the resin dry completely before moving the table top.
With the bulk of the work on the stone tabletop complete, the last major phase of the project is to create the metal base and, finally, join the top to the base. For this piece, the base is created from several pieces of metal salvaged from a junkyard: a piece of cylindrical schedule-40 pipe, a plow disc base and leaf springs from an old truck. Unless you are experienced with welding techniques and safety, take your design and metal to a welding shop or create a different type of base.
You can choose any height that you desire. Cut the pipe to size using a cutoff saw with an abrasive blade (Image 1). Smooth and grind away rust from the cut edges of the pipe. Do the same thing with the plow disc base by tracing the area where the pipe sits and then grinding away the rust in a ring. When welding the pipe to the plow disc base, clean metal should sit on clean metal.
Make sure the pipe is sitting level on top of the base. This is where a magnetic level comes in handy. If you need to make adjustments, use whatever you have, like knives or chisels, to hold it in place until the pieces are welded together. Tack the pipe to the base to hold it in place and then go around welding the entire base in sections (Image 2). Once the two pieces are welded together, clean off the old rust on the new base (Image 3) with an angle grinder and a grinding stone.
The base is nearly complete, but it needs something to provide support along the length of the heavy table top. Place two steel strips nearly parallel into the pipe portion of the base to get this strength. Using a cutoff saw, cut the leaf springs of an old truck to length, cut out two notches on either side of the pipe using a plasma cutter (Image 4) and set the springs into each notch. Level the springs, tack weld them, and then weld the entire thing into place.