Screen separators and a screen tensioning system for separators that facilitates rapid measurement of screen tension. Each separator subframe screen is suspended between opposed subframe walls. Suitable linkages distribute vibration during the aggregate sifting process. Screen edge flanges are secured by tensioners that control a screen suspension bracket. A carriage bolt fitted through bracket orifices and the walls coaxially receive a resilient grommet captivated by an adjustable sleeve nut. As the nut is tightened, screen tension increases and the grommet diameter increases. A portable gauge with an internal U-shaped measurement sleeve is fitted over the deformed grommet to measure screen tension. A plurality of gauge calibration points bordering the deformed grommet determine applied screen tension.