Pipe wrench Pipe wrench A pipe wrench is any of several types of wrench that are designed to turn threaded pipe and pipe fittings for assembly (tightening) or disassembly (loosening). Especially in North America, the Stillson wrench or Stillson-pattern wrench is the usual form of pipe wrench. (The name comes from the original patent holder, who licensed the pattern to multiple manufacturers; the patent expired decades ago.) Another type of wrench often used on pipes, the plumber wrench, is also often called a pipe wrench, depending on locale. The Stillson type is an adjustable wrench/spanner with hardened serrated teeth on its jaws;
Tool steel to the water-hardening class. These alloys increase the steels' hardenability, and thus require a less severe quenching process and as a result are less likely to crack. They have high surface hardness and are often used to make knife blades. The machinability of the oil hardening grades is high but for the high carbon-chromium types is low. This series includes an O1 type, an O2 type, an O6 type and an O7 type. All steels in this group are typically hardened at 800°C, oil quenched, then tempered at <200°C. The first air-hardening-grade tool steel was mushet steel, which was known