Common engineering abbreviations include AC for air conditioning, QTY for quantity, CTR for center, NO for number and LH for left hand. Less easily recognized abbreviations used in engineering include AFL, which stands for either above floor level or above finished level; DN for diameter nominal; FSBL, indicating a full strength butt weld; and UA, or unequal angle.
Other well-known abbreviations used in engineering include SQ for square, MM for millimeters, QC for quality control, DIA for diameter and REQ'D for required. Electrical engineering abbreviations include KWh for kilowatt hour, MHz for megahertz, CKT indicating a circuit and DC for direct current. CU can mean copper, cubic or coefficient of utilization depending on the context. In construction, DD represents either a driveway or deck drain, ELP stands for emergency lighting panel, SSL signifies structural slab level and TB is for tie beam.
Other common engineering abbreviations used to denote various engineering materials include DDS, indicating deep drawing steel, SR for stress relieved, W Steel for weathering grade steel and X Steel for low alloy grade steel. TCT refers to tungsten carbide tipped, SCHQ to special cold heading quality, MMC to metal matrix composite and NHT is for not heat treated.
Engineering abbreviations and acronyms occasionally vary by field of engineering. For example, CASE stands for computer aided software engineering in aeronautics and in automotive engineering for cranking angle sensing error.