If your vat has adjustable tension using a torque wrench when tightening the tension bolts allow you to keep your vats FEP film at an even and consistent tension for printing and between FEP replacements. If you use a gasket on your vat using a torque wrench when tightening your vats clamp bolts ensures an even clamp pressure on the gasket so that the FEP film will not slip under tension and that there is no possibility of resin leaking through a part of the gasket that is over or under tightened.
The torques needed for vat gaskets and tensioning can be surprisingly small, the clamp bolt torque for the bolts on http://projectsinterestsandetcetera.com/drumhead-flexvat-for-the-littlerp-3d-printer/ is only 16 ounce inches on each bolt, the tensioning bolts are also torqued to 16 ounce inches. On a larger vat (since upgraded to a foam gasket) http://projectsinterestsandetcetera.com/sla-3d-printer-drumhead-fep-flexvat/ the bolt torques are 40 ounce inches for the clamp bolts and 130 ounce inches for the tensioning bolts.
Tools for setting torques this low are both expensive and hard to find (I know, I bought both Sturtevant PM5 and Sturtevant PM15 torque screwdrivers for my vat). This torque wrench design which is specifically for flexvats is a reasonably priced alternative to the other available options.
The torque wrench has 2 carbon fiber strip “torsion bars” that can be changed to cover the range of torques commonly needed for flexvats. Uses standard 1/4″ (6.35mm) shank bits or socket adapters.