Deposition rate
How much weld metal a process lays down per hour, and the figure that converts weld length and joint size into arc time on a fabrication quote.
Deposition rate is the bridge between what a drawing shows and what a weldment costs. Measure the total weld length, work out the fillet size each joint calls for, and the volume of deposit follows from geometry. Divide by the deposition rate and you have arc time.
The number varies by process, by position and by operator. A wire process running flat lays down far more per hour than the same joint run out of position, which is why a fixture that cannot rotate the assembly is a cost decision as well as a handling one.
Arc time is not welder time, and confusing the 2 is the most common fabrication estimating error. Repositioning, tacking, cleanup, and the simple fact that nobody welds continuously mean the hours booked are typically well above the calculated arc time.
The ratio between them is worth knowing for your own floor, because it varies with the work and it is the single most useful figure in weldment estimating. It comes from your own job history rather than from a handbook.