Short answers, pulled from the story.
The first chisel emerged from the Neolithic era around 4100 to 2700 BCE in Schleswig-Holstein, Germany. These ancient tools were knapped from stone rather than forged in fire. This innovation allowed early humans to transition from simple scraping to precise carving of hard materials.
Woodworking utilizes a firmer chisel for heavy work, a bevel edge chisel for acute angles, and a mortise chisel for creating timber joints. Other types include the paring chisel for cleaning grooves, the skew chisel with a 60-degree cutting angle, and the dovetail chisel for intricate joints. The corner chisel features an L-shaped edge to clean out square holes and corners.
Cold chisels are made of tempered steel and cut metals without heating torches or forges. The head of a cold chisel is chamfered to slow the formation of a mushroom shape and is left soft to avoid brittle fracture. Hot chisels are used to cut metal that has been heated in a forge to soften it.
Masonry chisels are used to carve or cut stone, bricks, and concrete slabs with heavy force. Types include moil chisels, flat chisels, asphalt cutters, and the plugging chisel which has a tapered edge for cleaning out hardened mortar. These tools are often mounted on a hammer drill or jackhammer and can weigh three pounds or more.
The sweep number system expresses the part of a circle defined by the curve of the blade and ranges from #1 for flat to #9 for a semi-circle. Specialized gouges include the U-shaped #11 and the v-tool or parting tool which may be number #41. This system allows craftspersons to cut into areas not accessible with regular straight-bladed gouges.