For 1000s of years now man has been using stone masonry tools to carve and shape stone, into all kinds of objects and items. Stone masons tools have not changed significantly since the technique of forging steel was developed. The pneumatic hammer was introduced between 1885 and 1890 (powered by huge steam driven air compressors), and has pretty much replaced the wooden mallet and iron hammer. Carbide tipped tools began appearing in the middle of the 20th century. Most limestone carvers still prefer the old hand forged chisels, and keep a wooden mallet close at hand. The basic concepts of carved stone work haven’t changed much in thousands of years, even as the tools have slowly evolved.
The three basic types of chisels remain the same: a point for roughing out the stone, tooth chisels (also called claw tools) for shaping and modelling the forms, and flat chisels for the finished surfaces and details. Within each class there are endless variations; for example gouges, bull-noses and mitre tools are all variations on the flat chisel.
The point is the workhorse of the chisels. It is used for roughing out and removing material quickly. On soft stone, the point chisel can leave a ‘stone bruise’, or white mark, when it has gone deeper into the stone than your intended surface. Care must be taken not to ‘bury’ the chisel into the stone. These unintended white marks will show up when the stone is polished. These bruises can only be removed by carving or filing down into the stone past the depth of the bruise.
The tooth chisel is used after the point chisel has roughed out the basic shape. It further refines the forms and removes the peaks and valleys left by the point chisel.
The flat chisels come into play for smoothing out the texture left by the tooth chisel and prepares the stone for finishing. Any stone bruises left by the point or tooth chisels can be removed with a flat chisel.
The 3 pound mallet or hammer has sufficient weight to effectively drive a point chisel or pitching tool in removing large chunks of stone.
The pitching tool is used for knocking large chunks of stone off the edge of a square block. It can be very effective in removing a lot of stone quickly.
The tracing tool is used for creating a more precise line along the edge of a block.
DO – Sharpen your chisel blade as soon as you notice it is working harder to achieve the same affect.
DO – Grind the striking end of your chisel when it begins to distort – before it begins to "mushroom".
DO – Choose a chisel width that allows full blade contact with the stone. Selecting too wide a chisel for rough or irregular stone can result in carbide breakage.
DO – Allow bushing chisels to move freely (or "dance") on the stone. If held in one position they may jam, which can cause the carbide to break.
DO – Bevel the corners on your carbide chisel blade slightly during sharpening, especially if you are using it on granite or other hard stone. The blade can be sharper if it is being used on marble or softer stone.
DO – Use a green wheel to sharpen carbide blades and a steel wheel to grind or trim steel blades and shanks. The green wheel (silicon carbide) should be 80 grit or finer so as not to leave heavy grind marks on the carbide blade. Remember, when regrinding a chisel, never cool the carbide blade by dipping it in water or oil.
DO – For safety reasons, use stone hammers only as they were intended to be used. Some are designed to strike stone, some to strike hand tools, some to strike another hammer, and some to be struck by another hammer.
DO – Always use safety glasses when using any chisel or hammer.
DON’T – Dip carbide-tipped chisels in water or oil when grinding.
DON’T – Throw or toss carbide-tipped chisels into a toolbox or anywhere else. Place them down with care as they are brittle and can break, especially if they hit steel or another carbide blade.
DON’T – Use the corner of any style chisel blade to strike stone. This is called "pointing" and can easily break the carbide. Use a Hand Point instead – it’s designed to take the abuse.
DON’T – Use a Striking Cap with stone carving chisels. These chisels are intended for use with air tools only.
DON’T – Use tooth chisel on granite or other hard stone. Rather, use a 4-PT or 9-PT solid-tooth bush chisel, rippers, flats or any other bushing tool.