| Abrasive 3 | (english) A substance capable of grinding away another material. |
| Abrasive Wear | (english) The displacement and / or detachment of metallic particles from a surface as a consequence of being exposed to flowing fluids or gases. |
| Abrasive Wheels | (english) Wheels of a hard abrasive, such as Carborundum used for grinding. |
| ABSOLUTE PRESSURE | (english) The indicated value of the weight of the earth's atmosphere. At sea level, this value is approximately 14.65 psi (pounds per square inch). |
| Ac1 | (english) The temperature at which austenite begins to form on heating. |
| Ac3 | (english) In hypoeutectoid steel, the temperature at which transformation of ferrite into austenite is completed upon heating. |
| Accm | (english) In hypereutectoid steel, the temperature at which cementite goes into complete solution with austenite. |
| Accordion Reed Steel | (english) Hardened, tempered, polished and blued or yellow flat steel with dressed edges. Carbon content about 1.00. Material has to possess good flatness, uniform hardness and high elasticity. |
| ACCUMULATOR | (english) A vessel, normally cylindrical, which is used to store fluid and gas for future release of the energy in the compressed fluid and gas. Normally contains a diaphragm or piston between the fluid (liquid) and gas chambers. Fluid is normally introduced at one end and the gas at the opposite end. |
| Accurate | (english) Conforms to a standard or tolerance. |